Dynamic electrical double layers at solid-liquid interfaces for energy-information flow

Classical EDL models at conductive solid-liquid interfaces

Early studies focused on conductive solid-liquid interfaces, where interfacial charges originate from electrochemical reactions and are compensated by counterions in the adjacent electrolyte. The resulting charge distribution is governed by a balance between electrostatic attraction, thermal motion, and ion diffusion. To describe this behavior, classical models including Helmholtz, Gouy-Chapman, and Gouy-Chapman-Stern (GCS) frameworks were developed [Figure 2]. These models progressively refined the understanding of interfacial screening by incorporating increasingly realistic physical effects. The Helmholtz model treats the interface as a rigid capacitor composed of a charged surface and a compact counterion layer, resulting in a linear potential drop and a strictly localized screening region [Figure 2A]^[50]. While conceptually simple, it neglects thermal motion and ionic redistribution. The Gouy-Chapman model introduces thermal fluctuations and ionic diffusion, leading to a spatially extended diffuse layer where ions are distributed according to Boltzmann statistics [Figure 2B]^[51,52]. This framework captures the exponential decay of potential into the bulk electrolyte but assumes point-like ions, which becomes invalid under high surface charge density. To resolve these limitations, the GCS model integrates a compact Stern layer with a diffuse layer [Figure 2C], explicitly accounting for finite ion size, specific adsorption, and spatial charge separation^[53]. This hybrid structure provides a more accurate description of real electrochemical interfaces, especially under moderate-to-high ionic strength conditions^[101-104]. This regime establishes a passive ionic screening framework governed by electrostatic equilibrium, forming the first stage of EDL evolution.

Figure 2. Evolution of classical EDL models at conductive solid-liquid interfaces. (A) Helmholtz model; (B) Gouy-Chapman model; (C) Gouy-Chapman-Stern model.

Two-step EDL model at non-conductive solid-liquid interfaces

Unlike conductive interfaces, non-conductive solid-liquid interfaces generate surface charges dynamically through interfacial processes. Consequently, EDL formation is no longer governed solely by ionic screening of fixed surface charges but by the coupled evolution of interfacial charge generation and ionic redistribution. The two-step EDL model [Figure 3], introduced by Wang et al., extended classical EDL theory by identifying interfacial electron transfer and surface ionization as the initiating processes of surface charge generation, followed by ionic redistribution to establish the EDL^[54-56]. Electron-cloud overlap between liquid molecules and non-conductive surfaces enables partial electron transfer, while simultaneous ion adsorption and dissociation further contribute to net surface charge accumulation. These charges define the inner Helmholtz plane (IHP), which acts as the driving source for subsequent ionic rearrangement. In the second step, the electrostatic field generated by these interfacial charges induces ion migration in the electrolyte, leading to the formation of the outer Helmholtz plane (OHP) and an extended diffuse layer governed by thermal motion and electrostatic interactions.

Figure 3. Schematic illustration of the two-step EDL model at non-conductive solid-liquid interfaces. Reprinted with permission from^[56] Copyright © 2022 American Chemical Society.

From a physical perspective, contact electrification at solid-liquid interfaces involves multiple characteristic scales spanning molecular charge transfer, interfacial electrostatic interactions, and ionic redistribution. The initial charge generation process originates from molecular-level interactions at the interface, including electron transfer and ion-related surface reactions, typically occurring within sub-nanometer to nanometer-scale interfacial regions. The associated energy landscape is governed by differences in interfacial electronic states, chemical potentials, hydration energies, and electrostatic interactions. Following charge generation, the compensating ionic rearrangement extends beyond the immediate contact region to establish Stern layers and diffuse layers, with characteristic dimensions determined by surface charge density and electrolyte properties, such as ionic strength and Debye length. The corresponding timescales span from rapid interfacial charge redistribution to slower ionic diffusion and relaxation processes, which regulate the transient and dynamic evolution of EDL structures. Understanding these coupled spatial, energetic, and temporal scales is essential for revealing how microscopic contact electrification events evolve into macroscopic energy conversion and information transduction phenomena. Unlike classical models, this framework explicitly couples charge formation and ionic redistribution as a unified process, revealing that non-conductive interfaces actively participate in EDL construction rather than serving as passive boundaries. This regime marks the transition from equilibrium screening to coupled interfacial charge generation and ionic reorganization.

Triboiontronics driven by triboelectrically induced ion polarization

The two-step EDL model resolved the formation mechanism of EDLs at non-conductive solid-liquid interfaces, yet it remained fundamentally a quasi-equilibrium description. A subsequent conceptual advance emerged with triboiontronics, in which triboelectrically induced ion polarization transforms EDLs from passively formed interfacial structures into dynamically reconfigurable ionic-electronic interfaces. In triboiontronic systems, triboelectrically generated surface charges create a long-range electrostatic field that penetrates the dielectric substrate and dynamically modulates interfacial ionic distributions. Recognizing this fundamentally nonequilibrium process, Li et al. established the triboiontronic dynamic EDL model [Figure 4], which extends the two-step EDL framework from describing interfacial charge formation to quantitatively capturing the spatiotemporal evolution of dynamic EDLs driven by triboelectrically induced ion polarization^[57]. This external field simultaneously influences both the Stern layer and diffuse layer, enabling dynamic tuning of ionic concentration, spatial asymmetry, and charge polarity. As a result, the EDL no longer behaves as a static equilibrium structure but evolves into a reconfigurable ionic system. Under forward triboelectric polarization [Figure 4A], the induced electric field drives anion accumulation at the interface while repelling cations, strengthening interfacial charge density and enhancing local potential gradients^[57]. In contrast, reverse polarization reverses the field direction [Figure 4B], triggering ion redistribution in the opposite direction and leading to complete reconstruction of the EDL configuration, including polarity inversion^[57]. Through this mechanism, ionic distributions become continuously programmable via mechanical stimuli, establishing a dynamic ionic regulation regime that bridges mechanical energy and interfacial ionic transport. This regime represents a transition from static formation-controlled interfaces to actively programmable ionic systems.

Figure 4. Triboelectrically induced ion polarization enables dynamic reconstruction of EDLs at non-conductive solid-liquid interfaces. (A) Forward polarization-induced EDL reconstruction; (B) Reverse polarization-induced EDL reconstruction.

Iontrovoltaic effect enabled by semiconductor–liquid EDL-SCR coupling

The evolution of dynamic EDLs extends interfacial physicochemistry beyond dielectric solid-liquid systems toward semiconductor-liquid interfaces, where electrolyte ion redistribution becomes intrinsically coupled with electronic carrier modulation in the semiconductor. This transition represents a further advancement of EDL theory, from purely ionic interfacial structures to coupled ionic-electronic interfaces governed by the mutual interaction between the EDL and the semiconductor SCR through a shared interfacial electric field. Within this framework, Li et al. recently introduced the iontrovoltaic effect [Figure 5], which describes interfacial energy conversion arising from dynamic EDL-SCR coupling^[94]. Unlike conventional electrochemical or photovoltaic processes, the iontrovoltaic effect originates from actively reconfigurable ionic-electronic interfacial fields, in which ionic redistribution and electronic carrier separation are simultaneously regulated by interfacial electrostatics without the need for external bias^[94].

Figure 5. Dynamic EDL-SCR coupling underlying iontrovoltaic effects. Reprinted with permission from^[94] Copyright © 2026, Springer Nature. (A) Formation of coupled SCR-EDL structures at semiconductor-liquid interfaces; (B) Triboelectric polarization enhances interfacial field strength and modulates EDL-SCR coupling; (C) Asymmetric EDLs induce ionic chemical potential gradients, enabling directional ion and carrier transport.

When a liquid droplet contacts a semiconductor surface [Figure 5A], contact electrification and electrochemical potential equilibration drive interfacial charge redistribution, simultaneously generating an SCR in the semiconductor and a compensating EDL at the contact interface^[94]. This process establishes an EDL-SCR structure with a built-in electric field that governs carrier separation in the semiconductor. Importantly, this field is not static but dynamically evolves with interfacial conditions, making the system highly sensitive to external perturbations. To further regulate this coupled system, triboelectric polarization can be introduced [Figure 5B]. The externally generated electrostatic field extends across the interface, coupling the electronic response of the semiconductor with the ionic response of the electrolyte. In the semiconductor, it intensifies band bending and SCR formation, while in the electrolyte, it drives ion redistribution and dynamic EDL polarization. This reciprocal ionic-electronic modulation amplifies the interfacial electric field, giving rise to a highly coupled EDL-SCR state that underpins iontrovoltaic signal generation. Quantitatively, the strength of EDL-SCR coupling is governed by the charge densities and capacitances of the liquid-side EDL and semiconductor SCR, together with the corresponding interfacial potential drops. Variations in EDL charge density regulate ionic screening and local interfacial potential, whereas changes in SCR charge density modify band bending and carrier separation. Because the EDL and SCR are electrostatically coupled across the same interface, redistribution of charge on either side alters the overall interfacial electric field. The temporal response of this coupled state is further determined by the characteristic timescales of ionic redistribution in the electrolyte and carrier relaxation in the semiconductor, which together control how rapidly the interfacial energy landscape can be reconstructed under external stimulation. When a second semiconductor-liquid interface with a different interfacial state is introduced [Figure 5C], asymmetric EDL-SCR coupling is established across the electrolyte. This asymmetry generates an ionic chemical potential gradient that drives directional ion migration, while the coupled SCRs in the semiconductor electrodes regulate carrier transport. The coordinated evolution of ionic and electronic processes enables synchronized ionic-electronic responses across the entire system. Beyond triboelectric regulation, optical excitation provides an additional modulation pathway. Photoexcited carriers are separated by the interfacial electric field, while interfacial redox reactions continuously reshape local ionic distributions and reinforce EDL asymmetry. In parallel, photothermal effects enhance ionic mobility, accelerating interfacial charge redistribution dynamics. Through the synergistic coupling of triboelectric polarization, optical excitation, thermal modulation, EDL reconstruction, SCR regulation, and carrier separation, a dynamically reconfigurable ionic-electronic energy landscape is established. The iontrovoltaic effect therefore represents a new paradigm of interfacial energy conversion, in which ionic transport in electrolytes and electronic carrier dynamics in semiconductors are no longer independent processes, but are intrinsically coupled through a unified and dynamically evolving interfacial electric field. Within this EDL-SCR framework, semiconductor-liquid interfaces are transformed from passive charge-transfer boundaries into adaptive ionic-electronic systems governed by coupled electrostatic, ionic, and electronic degrees of freedom. This concept provides a unified physical foundation for iontrovoltaic energy conversion and the development of emerging iontronic technologies.

Collectively, the four EDL frameworks represent a progressive expansion in both interfacial scope and regulatory capability. Classical EDL models, including the Helmholtz, Gouy-Chapman, and GCS frameworks, mainly describe equilibrium or near-equilibrium ionic screening at conductive solid-liquid interfaces, providing the fundamental electrostatic basis for understanding interfacial charge compensation, but without explicitly considering the generation of surface charge or externally driven nonequilibrium reconstruction. The two-step EDL model extends this description to non-conductive interfaces by coupling interfacial charge generation, including electron transfer and surface ionization, with subsequent ionic redistribution, thereby explaining how EDLs are established at dielectric interfaces, although the model is still primarily concerned with EDL formation and relaxation toward quasi-equilibrium states. The triboiontronic dynamic EDL model further introduces triboelectrically induced ion polarization as an external driving mechanism, enabling active, reversible, and programmable reconstruction of ionic concentration distributions and interfacial charge states beyond spontaneous equilibration, but it mainly focuses on ionic redistribution and electrostatic regulation without explicitly incorporating semiconductor carrier energetics. The semiconductor-liquid EDL-SCR framework further expands this picture by coupling liquid-side ionic redistribution with semiconductor SCR formation, band bending, and carrier transport through a shared interfacial electric field, thereby extending EDL regulation from purely ionic processes to coupled ionic-electronic interfaces. Therefore, these four models should not be regarded as mutually exclusive replacements, but rather as progressively expanded descriptions of solid-liquid interfacial physics, evolving from passive ionic screening, to charge-generation and ion-redistribution coupling, to actively programmable ionic regulation, and ultimately to dynamic ionic-electronic coupling.

S-L TENGs

Energy conversion at solid-liquid interfaces is fundamentally governed by interfacial charge generation, separation, and transport. For conventional S-L TENGs, the basic operating mechanism is based on the coupling between contact electrification and electrostatic induction. At dielectric solid-liquid interfaces, contact electrification generates interfacial surface charges, corresponding to the initial charge-generation step of the two-step EDL model, while subsequent redistribution of mobile ions establishes the compensating EDL. Dynamic EDLs therefore provide a liquid-side ionic framework in which charge redistribution, ionic migration, and electrostatic field modulation are intrinsically coupled. Other factors, including wetting behavior, charge trapping, surface properties, and liquid composition, can further regulate charge generation, retention, ionic screening, and consequently the output performance. S-L TENGs are among the earliest and most representative systems in which contact electrification, dynamic EDL evolution, and electrostatic induction are coupled at dielectric solid-liquid interfaces^[108-112]. Since the first demonstration of S-L TENG by Wang et al., they have enabled efficient conversion of low-frequency mechanical energy from droplets, waves, and fluid flows into electricity^[92,113-118]. In contrast to solid-solid systems, the presence of a liquid introduces mobile ions, making EDL formation and evolution an inherent part of the energy conversion process^[119,120]. Quantitatively, the ionic contribution to S-L TENG operation is governed by several interfacial parameters, including surface charge density, Debye length, and EDL capacitance. The surface charge density generated by contact electrification determines the electrostatic driving strength for ionic redistribution, while the Debye length defines the characteristic spatial scale of ionic screening in the liquid and decreases with increasing ionic strength. Correspondingly, the EDL capacitance reflects the ability of the interface to accommodate compensating ionic charge and determines the relationship between interfacial charge accumulation and potential variation. These parameters collectively regulate the degree of ionic screening and the magnitude of interfacial potential modulation, thereby influencing the electrostatic-induction output of S-L TENGs.

S-L TENG operation can be interpreted as a cyclic evolution of dynamic EDLs, where interfacial contact induces charge generation and EDL formation, while separation triggers EDL disruption and ionic redistribution, generating transient interfacial electric fields that drive electron flow in external circuits [Figure 6]. Upon contact between a dielectric surface and a liquid, interfacial charge transfer associated with contact electrification induces ionic redistribution in the electrolyte, leading to the formation of an EDL at the interface [Figure 6A]. During separation, the disruption of this equilibrium state drives diffuse ions away from the interface, weakens electrostatic screening, and generates a transient interfacial electric field that drives electron flow in the external circuit [Figure 6B]. When complete separation is achieved, ionic redistribution approaches a quasi-equilibrium state and the output gradually diminishes [Figure 6C]. Upon re-approach, the interfacial electric field is re-established in the opposite direction, triggering EDL reconstruction and restoring ionic screening, thereby producing alternating current output [Figure 6D]. From this perspective, the operation of S-L TENGs is not solely governed by triboelectric charge induction but is fundamentally dictated by the cyclic reconstruction of dynamic EDLs. This process continuously modulates interfacial electrostatics and governs the coupling between ionic transport in the electrolyte and electron flow in the external circuit. Accordingly, the cyclic evolution of EDLs represents the intrinsic physicochemical origin of energy conversion in S-L TENG systems.

Figure 6. Dynamic EDL-mediated energy-conversion mechanism of S-L TENGs. (A) Contact between a dielectric surface and a liquid induces interfacial charge transfer and ionic redistribution, leading to EDL formation at the interface; (B) Subsequent separation disrupts the EDL, driving ionic migration and generating a transient interfacial electric field that induces electron flow in the external circuit; (C) At complete separation, ionic redistribution approaches a quasi-equilibrium state, corresponding to a maximum charge-separated condition with negligible current output; (D) Re-approach of the dielectric surface reconstructs the EDL, reverses ionic migration, and restores the interfacial electric field, resulting in alternating current output.

The evolution of S-L TENGs reflects the expanding understanding of interfacial ionic processes and dynamic EDLs at dielectric solid-liquid interfaces^[121-127]. Although the concept of dynamic EDLs was not explicitly formulated during the early stage of research, accumulating experimental evidence gradually revealed that interfacial ions and their redistribution play a decisive role in liquid-solid energy conversion, providing the experimental basis for later dynamic EDL theory. The first breakthrough was achieved in 2013, when Lin et al. demonstrated a water-based S-L TENG that converts mechanical energy from liquid waves into electricity through contact electrification between water and dielectric polymer surfaces [Figure 7A(i)]^[92]. At this stage, interfacial charge generation was interpreted primarily within the framework of triboelectric charge transfer; however, the presence of water inherently introduces an ionic environment, implying the formation of an interfacial ionic screening layer adjacent to the charged dielectric surface. From a modern perspective, this process corresponds to the establishment of an EDL, in which interfacial charges on the dielectric induce counterion accumulation and ionic rearrangement in the electrolyte. The device achieved an open-circuit voltage (V_OC) of ~80 V, a short-circuit current (I_SC) in the microampere range, and a peak power (P_R) density of ~50 mW m^-2 [Figure 7A(ii and iii)], confirming the feasibility of liquid-mediated triboelectric energy harvesting.

Figure 7. Pioneering developments of dynamic EDL-enabled S-L TENGs. (A) The first water-based S-L TENG (2013) provided early evidence that ionic structures at the liquid side participate in solid-liquid triboelectric energy conversion. Reprinted with permission from^[92] Copyright © 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim; (B) The droplet-driven S-L TENG (2014) revealed that droplet dynamics induce spatiotemporal evolution of interfacial charge distribution and dynamic EDL modulation. Reprinted with permission from^[128] Copyright © 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim; (C) The wave-driven S-L TENG (2014) demonstrated that continuous interfacial perturbations lead to dynamic EDL evolution and ionic redistribution, which directly govern macroscopic energy conversion behavior. Reprinted with permission from^[129] Copyright © 2014 American Chemical Society.

Subsequently, the system was extended to droplet-based S-L TENGs proposed by Lin et al. in 2014 [Figure 7B(i)], in which discrete droplet dynamics introduced a strongly time-dependent interfacial boundary condition^[128]. The droplet impact process, including approach, wetting, spreading, retraction, and detachment, induces continuous reconfiguration of the solid-liquid contact area and associated interfacial charge distribution. This dynamic evolution drives repeated formation, perturbation, and relaxation of ionic screening layers at the interface, which can now be interpreted as spatiotemporally evolving EDL structures. Importantly, this system provided clearer evidence that interfacial charge transfer and ionic redistribution are not independent processes but are intrinsically coupled through interfacial electrostatics. The device delivered a V_OC of up to ~9.3 V and an I_SC of ~17 μA [Figure 7B(ii and iii)], highlighting the sensitivity of interfacial energy conversion to dynamic wetting and ionic redistribution processes. A further conceptual advance was achieved in wave-driven S-L TENGs proposed by Zhu et al. in 2014 [Figure 7C(i)], where continuous water-level oscillations introduce a quasi-periodic modulation of the solid-liquid contact interface^[129]. In this configuration, interfacial charge accumulation on the dielectric surface and ionic rearrangement in the electrolyte occur simultaneously but continuously evolve with the instantaneous contact area. The resulting spatially distributed EDLs exhibit time-dependent restructuring along the interface, generating dynamic interfacial potential gradients that drive electron transport in the external circuit. This represents one of the earliest demonstrations that spatially and temporally evolving EDLs can directly govern macroscopic energy conversion behavior. The device achieved a V_OC of ~160 V, transferred charge (Q_SC) of ~75 nC, and P_R of ~0.12 mW, with performance positively correlated with wave velocity, indicating enhanced interfacial ion dynamics under stronger hydrodynamic perturbations [Figure 7C(ii and iii)].

The recognition of dynamic EDLs as active interfacial regulators has shifted the development of solid-liquid triboelectric systems from empirical optimization toward rational engineering of interfacial ionic processes for enhanced energy conversion^[130-135]. Rather than relying solely on conventional surface morphology design or material selection, recent studies have increasingly targeted the manipulation of ionic redistribution, interfacial polarization, and EDL evolution as key parameters governing charge-transfer efficiency and energy-conversion behavior. A representative example was reported by Chen et al. (2025), who demonstrated active enhancement of dynamic EDLs through interfacial polarization engineering [Figure 8A(i)]^[133]. By introducing a dielectric mismatch in a bilayer structure [Figure 8A(ii)], Maxwell-Wagner polarization generated a localized electric field enhancement at the solid-liquid interface. This intensified interfacial field strengthens charge trapping and promotes EDL formation, thereby enhancing charge separation during droplet impact. As a result, significantly improved electrical outputs were achieved, including a V_OC of ~540 V, an I_SC approaching 2 mA, highlighting the effectiveness of polarization-engineered EDL regulation [Figure 8A(iii)]. More recently, Gong et al. (2026) further extended interfacial engineering strategies to three-phase force-regulated solid-liquid systems [Figure 8B(i)]^[136]. By tuning surface tension, Laplace pressure, viscous resistance, and contact-line dynamics, stable liquid-slider operation was achieved while maintaining conformal solid-liquid contact [Figure 8B(ii)]. This configuration effectively optimizes interfacial charge transfer by simultaneously enhancing contact area, reducing mechanical losses, and stabilizing dynamic EDL evolution. The device delivered a Q_SC of ~580 nC, an I_SC of 5 μA, and a P_R of 3.14 mW, while maintaining long-term stability and achieving an energy conversion efficiency of 63.47%. Moreover, ionic content in the liquid was identified as a critical factor, where deionized water enabled higher outputs due to reduced electrostatic screening compared with ionic-rich tap water, further confirming the dominant role of EDL screening in interfacial energy conversion [Figure 8B(iii)].

Figure 8. Representative strategies for enhancing energy conversion of S-L TENG through interfacial ionic regulation and engineering. (A) An interfacial polarization-enhanced liquid-droplet triboelectric nanogenerator based on dielectric-constant mismatch and Maxwell-Wagner polarization was developed by Chen et al. in 2025. Reprinted with permission from^[133] Copyright © 2025 WILEY‐VCH GmbH; (B) A three-phase interfacial force-regulated solid-like liquid-slider triboelectric nanogenerator for highly efficient and robust energy harvesting was developed by Gong et al. in 2026. Reprinted with permission from^[136] Copyright © 2025 WILEY‐VCH GmbH.

Collectively, advances in S-L TENGs demonstrate a continuous evolution from simple triboelectric charge transfer to interfacial energy conversion governed by dynamic EDL regulation. Across different engineering strategies, including physicochemical environment tuning, interfacial polarization enhancement, and three-phase force modulation, the interfacial ionic environment emerges as a central parameter that governs charge separation, electrostatic field formation, and energy-conversion efficiency. In this framework, the EDL evolves from a passive ionic screening structure into a dynamically reconfigurable interfacial entity that mediates the coupling between ionic transport in the electrolyte and electrostatic induction in the external circuit. The performance of S-L TENGs is therefore fundamentally determined by the interplay between interfacial charge generation, ionic redistribution, and EDL screening dynamics, rather than solely by surface morphology or material properties. This unified perspective establishes dynamic EDL regulation as a general design principle for solid-liquid energy harvesting systems, providing a mechanistic foundation for optimizing interfacial electrostatics, enhancing charge-transfer efficiency, and enabling scalable energy conversion from complex fluid environments.

TINGs enabled by ionic migration between asymmetric EDLs

While dynamic EDLs in S-L TENGs primarily facilitate electron-mediated energy conversion through electrostatic induction, recent advances in interfacial physicochemistry have revealed a broader functionality of dynamic EDLs: their capacity to actively regulate ionic transport. In biological systems, dynamically regulated physicochemical interfaces establish and maintain ionic concentration gradients that drive directional ion migration, enabling efficient energy transfer and information signaling. Inspired by these principles, Li et al. developed TING in 2024 based on asymmetric dynamic EDLs at coupled solid-liquid interfaces^[137]. This work established dynamic EDLs as programmable ionic regulators capable of mediating not only charge accumulation but also directional ionic transport and information encoding [Figure 9]. In this system, sequential contact between a water droplet and two metal/dielectric hybrid interfaces with different contact histories leads to spatially asymmetric charge distributions. According to the two-step EDL framework, each contact event induces the formation of an EDL through interfacial charge transfer and ionic redistribution. Because the two interfaces are generated under different interfacial states, asymmetric EDL configurations are established across the liquid phase. This asymmetry gives rise to a sustained ionic concentration gradient, which drives directional ionic migration through the electrolyte. Quantitatively, the driving force for this directional ionic transport is governed by the electrochemical-potential difference established between the asymmetric EDLs, which contains contributions from both the ionic concentration gradient and the interfacial electric-potential gradient. A larger concentration difference between the two interfaces generally produces a stronger chemical-potential imbalance and enhances directional ionic flux, while the resulting transport rate is further influenced by ion mobility, diffusivity, valence, and the effective transport distance. In the temporal domain, the persistence of the asymmetric EDL state relative to ionic diffusion and relaxation timescales determines how long the concentration gradient can be maintained and therefore directly affects the duration and stability. Concurrently, ionic-electronic coupling at the interfaces enables charge extraction in the external circuit, resulting in a stable direct-current (DC) output. From the perspective of dynamic EDL evolution, the key advance of TINGs lies in transitioning from transient electrostatic modulation to the deliberate construction of spatially asymmetric EDL architectures that sustain ionic chemical potential gradients. In this regime, triboelectrically induced interfacial polarization is converted into a persistent driving force for ionic transport, fundamentally distinguishing TINGs from S-L TENGs. This establishes dynamic EDLs not only as regulators of interfacial electrostatics but also as active mediators of ionic flux, providing the physicochemical basis for triboiontronic energy transfer and ionic signal transport systems^[137].

Figure 9. Schematic illustration of the operating mechanism of TINGs, where asymmetric dynamic EDLs at coupled solid-liquid interfaces establish ionic concentration gradients that drive directional ionic migration and enable DC energy conversion.

Based on the asymmetric EDL-driven ionic migration mechanism, a TING was developed using Au/FEP (fluorinated ethylene propylene) hybrid films in 2024 [Figure 10A]^[137]. In this architecture, the Au layer serves as an efficient charge-collecting electrode, while the exposed FEP regions enable robust EDL formation through contact electrification with water, providing a well-defined platform for investigating asymmetric interfacial ionic transport. To validate the governing mechanism, controlled wetting-sequence experiments were performed [Figure 10B]. The device output exhibited a clear dependence on the temporal order of interfacial EDL formation: wetting of the lower interface prior to the upper interface produced a positive output, whereas reversing the sequence led to polarity inversion. Nearly synchronous wetting resulted in negligible signals. Moreover, increasing the temporal asymmetry between the two interfaces significantly enhanced the output intensity, confirming that the electrical response originates from asymmetric EDL-induced ionic concentration gradients rather than conventional electrostatic induction. These results establish a direct correlation between EDL asymmetry and directional ionic transport. The role of the hybrid architecture was further clarified by tuning Au sputtering time [Figure 10C]. Increasing Au coverage enhances electrical conductivity and facilitates ionic-electronic coupling, whereas excessive deposition reduces exposed FEP area, thereby weakening interfacial charge generation and EDL formation. This competition leads to an optimal structural balance, highlighting the necessity of simultaneously optimizing charge collection efficiency and interfacial electrostatic activity. To further elucidate the origin of asymmetric EDL formation, interfacial charge behaviors on dielectric, metallic, and hybrid surfaces were systematically compared [Figure 10D]. Dielectric interfaces favor strong contact electrification and pronounced EDL formation but suffer from limited charge extraction. Metallic interfaces provide efficient electron transport pathways, but exhibit weakened EDL formation due to rapid charge dissipation. In contrast, Au/FEP hybrid interfaces integrate both advantages: the dielectric component sustains robust EDL formation, while the metallic layer ensures efficient charge collection and external circuit coupling. This synergistic configuration enables the coexistence of asymmetric EDL construction, sustained ionic concentration gradients, and effective ionic-electronic coupling, thereby forming the physical basis of triboiontronic energy conversion.

Figure 10. Asymmetric EDL-driven ionic transport and ionic-electronic coupled energy conversion in TINGs. Reprinted with permission from^[137] Copyright © 2024 Springer Nature. (A) Construction of a TING based on Au/FEP hybrid interfaces enabling asymmetric EDL formation and ionic transport; (B) Experimental verification of directional ion migration induced by asymmetric EDLs through controlled wetting-sequence measurements; (C) Regulation of triboiontronic output via structural optimization of metal/dielectric hybrid interfaces, balancing charge collection and EDL formation; (D) Comparative EDL configurations at dielectric, metallic, and hybrid interfaces, highlighting their distinct roles in charge generation and transport; (E) DC output arising solely from asymmetric EDL-driven ionic migration; (F) Enhancement of ionic transport through synergistic coupling between asymmetric EDL-induced concentration gradients and interfacial redox reactions; (G) Overall performance enhancement of triboiontronic energy conversion enabled by asymmetric EDL-redox coupling.

Following the identification of asymmetric EDL-driven ionic transport as the dominant mechanism, the electrical characteristics of TINGs arising exclusively from EDL asymmetry were systematically investigated. Owing to sustained directional ion migration induced by coupled asymmetric EDLs, the device generates stable DC outputs. Under optimized conditions, the TING achieves an I_SC of 2.60 mA and a V_OC of 0.25 V. More importantly, the Q_SC density and P_R density reach 412.54 mC m^-2 [Figure 10E] and 8.45 W m^-2, respectively, confirming that asymmetric EDLs alone can continuously convert interfacial ionic concentration gradients into electrical energy without requiring external bias, mechanical pumping, or electrochemical driving forces. This establishes asymmetric EDLs as an intrinsic ionic transport medium for triboiontronic energy conversion. To further enhance ionic transport, metallic current-collecting layers with tunable electrochemical activity were introduced to couple asymmetric EDL-driven ion migration with interfacial redox reactions [Figure 10F(i)]. In addition to the ionic concentration gradients generated by asymmetric EDLs, spontaneous oxidation-reduction processes at the metal-liquid interface continuously produce additional ionic species and reinforce interfacial chemical potential differences. The coupling effect was validated through controlled wetting-sequence experiments [Figure 10F(ii)]. Ionic flux driven by EDL asymmetry could either synergize with or oppose redox-induced ionic transport. When both contributions aligned, ionic transport and electrical outputs were significantly enhanced; when they opposed each other, partial cancellation occurred, leading to reduced performance. Benefiting from this synergistic EDL-redox coupling, substantially enhanced triboiontronic outputs were achieved. Compared with the asymmetric EDL-only configuration, the coupled system exhibits markedly improved current, charge transfer, and power generation capabilities, reaching an I_SC of 5.58 mA, a Q_SC density of 540.70 mC m^-2, and a P_R density of 38.64 W m^-2 [Figure 10G(i-iii)]^[137]. These enhancements originate from the cooperative interaction between EDL-induced ionic concentration gradients and redox-generated ionic flux, which together amplify both ion migration and ionic-electronic coupling efficiency. Collectively, this work establishes asymmetric EDL formation as the fundamental driving force for triboiontronic energy conversion and demonstrates that ionic transport can be further amplified through coupling with interfacial redox chemistry. More importantly, it redefines dynamic EDLs from passive charge-screening structures into active ionic transport and energy conversion interfaces, providing a systematic experimental foundation for asymmetric EDL-driven triboiontronics.

A further advance in triboiontronics was achieved through triboelectrically induced ion polarization, which enables active reconstruction of ionic concentration distributions within EDLs at solid-liquid interfaces. Unlike conventional TINGs, where ionic transport is governed by spontaneously formed asymmetric EDLs, this polarization strategy introduces an externally generated triboelectric field that actively modulates existing EDL structures, providing an additional degree of freedom for regulating ionic distribution and ionic-electronic coupling^[93]. This concept establishes a route toward programmable control of ionic flux and lays the physicochemical foundation for neuromimetic iontronic systems. The operating mechanism is illustrated in Figure 11. Upon contact between the water droplet and the bottom Au/FEP hybrid film, interfacial contact electrification occurs at the exposed dielectric regions, leading to the formation of an EDL at the solid-liquid interface [Figure 11A]. Subsequently, the top Au/FEP electrode undergoes solid-solid contact electrification with an electropositive fur layer, generating triboelectric charges on the FEP surface [Figure 11B]. After separation, the retained surface charges establish a localized electric field that penetrates the liquid phase and modulates ion distribution within the pre-existing bottom EDL [Figure 11C]. Under this field, ionic concentration within the EDL becomes strongly polarized, with enhanced accumulation of anions near the interface and redistribution of cations toward the diffuse layer, leading to a pronounced nonequilibrium ionic asymmetry. When the top electrode recontacts the droplet, a second EDL is formed at the upper interface [Figure 11D]. Because the bottom EDL has already been externally polarized, a significant ionic concentration difference is established between the two interfaces, which drives rapid directional ion migration through the liquid phase. The resulting ionic flux induces charge redistribution at the electrodes via ionic-electronic coupling, enabling efficient electrical signal generation. More importantly, triboelectrically induced ion polarization fundamentally extends the regulatory capability of dynamic EDLs from spontaneous formation processes to active, field-programmable reconstruction of interfacial ionic states. In this regime, EDLs are no longer passive screening layers but reconfigurable electrochemical interfaces capable of encoding, amplifying, and directing ionic fluxes. This mechanism not only enhances triboiontronic energy conversion but also provides a general strategy for coupling ionic transport with signal modulation, offering a key step toward dynamic EDL-enabled energy-information integration.

Figure 11. Dynamic regulation of EDLs via triboelectrically induced ion polarization for enhanced triboiontronic energy conversion in TINGs. (A) Formation of the initial EDL at the bottom Au/FEP-water interface through solid-liquid contact electrification; (B) Generation of triboelectric charges on the top FEP surface via solid-solid contact electrification with an electropositive fur layer; (C) Triboelectrically induced polarization field modulates the pre-formed EDL, driving active redistribution of ionic concentration and enhancing interfacial ionic asymmetry; (D) Formation of coupled asymmetric EDLs and amplified ionic concentration gradients, enabling directional ion migration and ionic-electronic coupled energy conversion.

Li et al. further developed a TING enhanced by triboelectrically induced ion polarization in 2025, enabling active regulation of interfacial ionic distributions for enhanced ionic energy conversion and programmable ionic transport [Figure 12A]^[93]. Inspired by Maxwell’s demon and biological ion pumps [Figure 12A(i and ii)], this concept establishes a unified framework in which triboelectric energy is converted into an external electrostatic driving field that actively reconstructs ionic configurations within EDLs [Figure 12A(iii)]. Analogous to adenosine triphosphate (ATP)-driven ion pumps that maintain nonequilibrium ionic gradients across neuronal membranes, triboelectrically induced polarization injects mechanical energy into the interfacial system, enabling ions to be driven against equilibrium distributions and forming highly polarized asymmetric EDL states. The resulting amplified ionic concentration gradients provide an enhanced driving force for directional ion migration and ionic-electronic coupled energy conversion. To verify this mechanism, remote ionic regulation experiments were conducted using a water droplet-polyethylene terephthalate (PET) interface [Figure 12B]. A triboelectrically charged FEP film or electropositive fur layer was positioned above the interface without physical contact, generating a remote polarization field. Experimental results show that a negatively charged FEP layer increases the droplet charge from 0.54 to 0.94 nC and shifts the substrate potential negatively, whereas a positively charged layer reduces the droplet charge to 0.25 nC. These observations confirm that externally applied triboelectric fields can non-contactly modulate ionic distributions within EDLs. Within the two-step EDL framework, the negative electrostatic field enhances anion accumulation at the interface and increases EDL charge density, whereas the positive electrostatic field weakens interfacial ionic asymmetry by promoting ion redistribution toward equilibrium. This establishes triboelectrically induced ion polarization as a Maxwell’s demon-like interfacial regulator that actively reconstructs EDL charge states through externally supplied mechanical energy. Having established active EDL regulation, the influence of interface architecture on triboiontronic output was further investigated [Figure 12C]. Pure dielectric interfaces enable strong EDL formation and large ionic concentration gradients but suffer from poor charge extraction due to limited conductivity. In contrast, metallic interfaces provide efficient electron transport, but exhibit weakened EDL formation. Hybrid metal/dielectric interfaces integrate these advantages: the dielectric component sustains asymmetric EDL formation, while the metallic layer enables efficient ionic-electronic coupling and charge collection. As a result, conventional TINGs based on Au/FEP hybrid interfaces generate an I_SC of 23.6 μA. More importantly, introducing triboelectrically induced ion polarization further amplifies EDL asymmetry, increasing the I_SC to 31.1 μA, thereby demonstrating that active field-driven reconstruction of EDLs provides an effective route to enhance ionic transport and triboiontronic energy conversion.

Figure 12. Triboelectrically induced ion polarization enabling active regulation of EDLs and higher-performance triboiontronic energy conversion. Reprinted with permission from^[93] Copyright © 2025 Elsevier Inc. (A) Conceptual framework of a triboiontronic Maxwell’s demon inspired by classical Maxwell’s demon and biological ion pumps, where triboelectric energy is converted into an external electrostatic field to actively generate nonequilibrium ionic concentration gradients within coupled EDLs; (B) Experimental demonstration of triboelectrically induced ion polarization via remote modulation of EDL charge distributions and interfacial electrostatic potentials; (C) Comparison of triboiontronic energy conversion performance across dielectric, metallic, and metal/dielectric hybrid interfaces, highlighting the synergistic roles of robust EDL formation and efficient ionic-electronic coupling; (D) Effects of electrolyte properties, including ionic concentration, valence state, and diffusion kinetics, on triboiontronic energy conversion behavior; (E) Demonstration of enhanced and programmable triboiontronic outputs enabled by triboelectrically induced ion polarization; (F) Synergistic enhancement of ionic transport and energy conversion through coupling triboelectrically induced ion polarization with interfacial redox reactions.

After optimizing the solid-phase interface, the role of ionic charge carriers in triboiontronic energy conversion was systematically investigated [Figure 12D]. Increasing the LiCl concentration from 10^-4 M to saturation continuously enhanced the I_SC from 0.14 to 2.22 mA. This improvement arises from the synergistic effects of increased ionic density within the EDL and enhanced electrolyte conductivity, both of which strengthen ionic transport and ionic-electronic coupling across the interface. Further enhancement was observed by tuning ion valence. Replacing Li⁺ with divalent Mg²⁺ ions increased the charge-carrying capacity of the electrolyte, leading to a maximum I_SC of 4.22 mA in saturated MgCl₂ solutions. This result highlights the critical role of ionic valence in governing interfacial charge density and EDL-mediated transport efficiency. Interestingly, AlCl₃ exhibits distinct transport behavior compared with monovalent and divalent electrolytes. Although lower-concentration AlCl₃ solutions produce higher outputs, the performance decreases at higher concentrations and eventually reverses polarity under saturated conditions. Molecular dynamics simulations reveal a nontrivial hierarchy of ion mobility (H⁺ > Cl^- > Al³⁺ In concentrated AlCl₃ solutions, strong hydrolysis leads to the dominance of highly mobile H⁺ species, which reshapes the effective EDL structure and alters the primary charge-transfer pathway, ultimately resulting in output polarity inversion. These results reveal that ionic transport in triboiontronic systems is dictated by a complex interplay among ionic concentration, valence, hydration structure, and diffusion kinetics, rather than by concentration and charge state alone. Rational co-engineering of interfacial architectures and ionic species therefore provides an effective strategy for enhancing triboiontronic outputs. Under optimized conditions, the TING delivered a P_R of 6.89 mW [Figure 12E]. More importantly, the system demonstrates that ionic transport directionality can be fundamentally regulated through electrolyte-dependent EDL reconstruction, enabling controllable modulation of output magnitude and polarity, with stable negative output reaching -1.79 mW. To further enhance both output magnitude and operational stability, interfacial redox reactions were integrated into the triboelectrically polarized system, forming a synergistically enhanced TING configuration. In this hybrid system, redox processes continuously generate additional ionic species and reinforce interfacial concentration gradients, thereby sustaining directional ion migration and strengthening ionic-electronic coupling. As a result, the ES-TING achieved a P_R of 34.67 mW [Figure 12F]. Correspondingly, the Q_SC density and P_R density reached 5,237.51 mC m^-2 and 346.7 W m^-2, respectively. These findings demonstrate that coupling triboelectrically induced ion polarization with interfacial redox chemistry provides a robust strategy to simultaneously amplify EDL asymmetry, sustain ionic transport, and enhance ionic-electronic energy conversion efficiency.

Taken together, TINGs represent a transition of dynamic EDLs from electrostatic induction-mediated interfaces to ion-transport-dominated energy conversion systems. In contrast to S-L TENGs, which rely on transient charge screening, TINGs exploit asymmetric EDLs to establish sustained ionic concentration gradients that drive directional ion migration and enable DC output. With triboelectrically induced ion polarization, EDLs are further transformed into actively tunable interfacial systems, where ionic distributions can be dynamically reconstructed to regulate ion flux direction, transport intensity, and output polarity. This introduces a programmable ionic transport mode beyond spontaneous interfacial equilibration. Furthermore, coupling interfacial redox reactions with polarized EDLs enhances both ionic generation and transport continuity, leading to improved ionic-electronic coupling and energy conversion efficiency. Collectively, TINGs establish a hierarchical evolution from asymmetric ionic transport to actively programmable ionic regulation.

IVNGs enabled by EDL-SCR coupling

Triboiontronic systems are fundamentally governed by asymmetric EDL-mediated ionic transport within electrolytes. Extending dynamic EDL regulation to semiconductor-liquid interfaces enables the coupling of ionic migration with electronic carrier modulation, representing a transition from purely ionic regulation toward integrated ionic-electronic functionality. Building upon the dynamic coupling between EDLs and semiconductor SCRs, the semiconductor-liquid iontrovoltaic effect introduces a new paradigm of interfacial energy conversion in which ionic and electronic processes are simultaneously regulated by a shared interfacial electric field [Figure 5]. Introduced by Li et al. in 2026, IVNGs represent a further evolution of dynamic EDL systems, extending their regulatory capability from charge generation and ionic transport at interfaces to coupled modulation of semiconductor carrier dynamics [Figure 13A]^[94]. In contrast to TINGs, where energy conversion is governed primarily by asymmetric EDL-driven ionic migration, IVNGs introduce semiconductor SCRs as an additional regulatory degree of freedom, enabling coordinated control of ionic redistribution in the electrolyte and carrier energetics in the semiconductor. To validate this concept, a series of experiments was performed to determine whether triboelectrically induced ion polarization can simultaneously modulate ionic distributions within EDLs and electronic states within SCRs. Local pH measurements showed reversible changes in H⁺ concentration under opposite polarization states [Figure 13B(i and ii)], providing direct evidence that external electrostatic fields can dynamically reconstruct interfacial ionic distributions and regulate the local electrochemical environment. At the same time, the effect of triboelectrically induced ion polarization on semiconductor energetics was investigated using Kelvin probe force microscopy (KPFM) and operando electrochemical characterization based on Mott-Schottky analysis. KPFM measurements revealed reversible shifts in the surface potential and work function of p-type silicon under opposite polarization states, demonstrating that the external electrostatic field can effectively modulate the electronic energy levels of the semiconductor [Figure 13C]. To further determine whether this regulation persists under realistic semiconductor-liquid operating conditions, in situ Mott-Schottky measurements were performed to probe the SCR properties at the semiconductor-electrolyte interface. Consistent shifts in flat-band potential were observed under different polarization conditions, confirming that triboelectric polarization can dynamically regulate semiconductor band bending and the interfacial electric field [Figure 13D]. Taken together, these results provide compelling evidence that triboelectrically induced ion polarization simultaneously modulates ionic distributions within EDLs and carrier energetics within SCRs. Such dynamic EDL-SCR coupling substantially strengthens the interfacial electric field and enhances the cooperative regulation of ionic and electronic charge distributions. As a consequence, IVNGs exhibit stronger ionic concentration gradients in the electrolyte, greater charge accumulation in the semiconductor, and more efficient directional ionic migration, ultimately leading to significantly enhanced electrical output [Figure 13E]. These findings demonstrate that dynamic EDL-SCR coupling establishes a new mechanism for iontronic energy conversion, in which ionic transport and semiconductor carrier dynamics are intrinsically integrated within a unified interfacial framework.

Figure 13. IVNG was developed by Li et al., and the dynamic EDL-SCR coupling and photo-enhanced iontrovoltaic energy conversion were experimentally verified. Reprinted with permission from^[94] Copyright © 2026, Springer Nature. (A) Device structure of the IVNG; (B) Experimental verification of triboelectric-polarization-induced ionic redistribution within EDLs through reversible variations in local pH and proton concentration under opposite polarization states; (C) Surface-potential characterization showing semiconductor work function modulation by triboelectrically induced ion polarization; (D) Semiconductor band bending and SCR charge density could be regulated by triboelectrically induced ion polarization; (E) Enhanced electrical output enabled by triboelectric-polarization-strengthened EDL-SCR interactions. (F) Photoexcitation introduces a further level of coupling between ionic transport and semiconductor carrier dynamics; (G) Synergistic enhancement of iontrovoltaic energy conversion through the cooperative effects of triboelectric polarization and photoexcitation.

Photoexcitation provides an additional pathway for coupling ionic transport with semiconductor carrier dynamics, further expanding the regulatory dimensions of dynamic EDL-SCR interfaces [Figure 13F(i)]. Under illumination, photogenerated electron-hole pairs are efficiently separated by the enhanced interfacial electric field within the coupled EDL-SCR system. Concurrently, photogenerated holes migrate toward the semiconductor-liquid interface, where they participate in interfacial oxidation reactions that generate additional ionic species, thereby further amplifying EDL asymmetry. As a result, photoinduced carrier separation and ionic transport become intrinsically interdependent rather than independent processes. The rapid disappearance of the enhanced output upon removal of illumination confirms that the observed response originates from reversible interfacial electrostatic modulation and electrochemical reactions, rather than irreversible chemical changes [Figure 13F(ii)]. When photoexcitation is coupled with triboelectric polarization, a pronounced synergistic enhancement is observed [Figure 13G]. The strengthened EDL-SCR electric field simultaneously promotes carrier separation in the semiconductor and accelerates interfacial redox kinetics, while photoinduced ionic generation continuously reinforces interfacial charge asymmetry. This positive-feedback loop establishes a dynamically reinforced EDL-SCR coupling state, leading to significantly enhanced ionic transport and energy conversion efficiency. Notably, the efficiency of this iontrovoltaic process critically depends on the directionality of the built-in interfacial electric field within the coupled EDL-SCR region. Only when the interfacial field simultaneously favors carrier separation and interfacial redox activation can photoexcitation effectively amplify ionic asymmetry and directional ion migration. These results highlight the central role of SCR energetics in governing ionic-electronic coupling and establish dynamic EDL-SCR interactions as the fundamental mechanism underpinning iontrovoltaic energy conversion.

Following the establishment of dynamic EDL-SCR coupling as the basis of the iontrovoltaic effect, research has shifted towards the rational design of ionic-electronic interfaces with controllable energy landscapes. As iontrovoltaic conversion is governed by the coupled evolution of ionic redistribution, semiconductor carrier dynamics and interfacial electrochemical processes, its performance can be optimized through simultaneous manipulation of band alignment, interfacial asymmetry, electrolyte chemistry and external-field interactions. Among these strategies, semiconductor work-function engineering provides the first demonstration that electronic energy landscapes can be tailored to regulate EDL-SCR coupling and iontrovoltaic output [Figure 14A]. By coupling p-type silicon with metal current collectors of different work functions, the iontrovoltaic output was found to be strongly dependent on metal-semiconductor band alignment. Low-work-function metals facilitate carrier extraction and interfacial charge transfer, whereas high-work-function metals induce interfacial field opposition that suppresses carrier collection. These results highlight band engineering as an effective route to regulate carrier dynamics and strengthen ionic-electronic coupling at semiconductor-liquid interfaces. Building on this principle, interfacial energetic asymmetry was further introduced to enhance dynamic EDL-SCR coupling. By replacing the top Au/p-Si electrode with a metal/FEP hybrid interface, a highly asymmetric dual-EDL configuration was constructed [Figure 14B(i)], which simultaneously enhances directional ionic migration and promotes hole-driven interfacial oxidation reactions. The generated ionic products further reinforce interfacial charge asymmetry, establishing a self-amplifying ionic environment that strengthens both EDL formation and ionic transport. As a result, a redox-coupled iontrovoltaic nanogenerator (RC-IVNG) was realized, in which ionic migration and interfacial electrochemical reactions jointly contribute to energy conversion. Finally, the integration of triboelectric polarization and photoexcitation further amplifies this coupled system. Triboelectrically induced ion polarization enhances both EDL asymmetry and SCR band bending, while photoexcited carriers participate in interfacial redox reactions that continuously generate additional ionic species. These processes collectively establish a positive-feedback loop among carrier separation, ionic generation, and directional ion transport. The RC-IVNG achieves significantly enhanced ionic transport and energy conversion performance, demonstrating a unified strategy for engineering higher-efficiency iontrovoltaic systems [Figure 14B(ii)].

Figure 14. Multidimensional engineering of dynamic EDL-SCR coupling toward higher-performance iontrovoltaic energy conversion. Reprinted with permission from^[94] Copyright © 2026, Springer Nature. (A) Solid-state band engineering via work-function modulation to regulate carrier energetics in semiconductor-liquid interfaces; (B) Enhancement of dynamic EDL-SCR coupling through redox-assisted ionic enrichment, strengthening interfacial electric fields and ionic-electronic interactions; (C) Electrolyte engineering for modulating EDL structure, ionic concentration, and transport kinetics; (D) Alkaline electrolyte-enabled ionic generation and enhanced photoactivated iontrovoltaic transduction via improved wettability and continuous interfacial redox processes; (E) Photothermal regulation of ionic mobility and transport kinetics within asymmetric EDLs under infrared irradiation. (F) Under optimized conditions, the RC-IVNG delivers an I_SC of ~12.6 mA and a P_R density of 541 W m^-2.

Beyond semiconductor band structures and interfacial asymmetry, electrolyte composition provides a critical handle for manipulating ionic transport, EDL evolution, and the resulting ionic-electronic coupling in iontrovoltaic systems [Figure 14C]. Increasing ionic strength compresses the EDL, reduces the Debye length, and accelerates ion migration within coupled EDL structures^[94]. In addition, electrolyte chemistry simultaneously modulates interfacial wettability and redox kinetics, thereby jointly influencing EDL formation density and ion-generation efficiency. Among various electrolytes, alkaline media exhibit particularly pronounced enhancement effects. In concentrated NaOH solutions, improved wettability promotes the formation of dense and stable EDLs, while non-passivating silicon oxidation continuously generates soluble ionic species, sustaining long-term interfacial charge replenishment and directional ion transport [Figure 14D(i)]. Under UV illumination, the resulting photoactivated RC-IVNG achieves milliampere-level current output, demonstrating the capability of dynamic EDL-SCR systems for high-flux ionic energy conversion [Figure 14D(ii)]. To further accelerate ionic transport, photothermal regulation was introduced via infrared irradiation [Figure 14E]. Owing to the strong absorption of water in the infrared regime, localized heating increases ionic mobility, decreases viscosity, and reduces internal resistance, thereby significantly enhancing ion diffusivity and transport kinetics within asymmetric EDLs. When photothermal activation is combined with triboelectric polarization, photoexcitation, and redox-driven ionic generation, a pronounced multiphysical-field synergistic effect emerges. Under optimized conditions, the RC-IVNG delivers an I_SC of ~12.6 mA [Figure 14F(i)], corresponding to a P_R density of 541 W m^-2 [Figure 14F(ii)]. This performance represents one of the highest reported outputs for dynamic EDL-enabled ionic energy conversion systems. Overall, IVNGs demonstrate that dynamic EDLs can extend beyond conventional ionic transport regulation and directly couple with semiconductor carrier dynamics through SCR modulation. The resulting EDL-SCR hybrid system enables coordinated control of interfacial electric fields, ionic migration, carrier separation, and redox reactions, establishing a unified framework for multiphysical-field iontronic energy conversion. These findings position dynamic EDL-SCR coupling as a general paradigm for next-generation solid-liquid interfacial energy transduction.

Experimentally, the iontrovoltaic contribution should be distinguished from conventional photoelectrochemical, redox/corrosion, and concentration-cell processes by examining the origin, controllability, and reversibility of the interfacial driving force. In a baseline IVNG, directional output can be generated in the absence of illumination and external bias through deliberately established asymmetry between coupled semiconductor-liquid EDL-SCR interfaces, distinguishing it from a purely photoelectrochemical process. The iontrovoltaic output is further correlated with reversible modulation of both liquid-side ionic distributions and semiconductor-side carrier energetics, as evidenced by polarization-dependent local ion-concentration changes, surface-potential/work-function shifts, and flat-band-potential variations. In contrast, conventional concentration cells derive their electromotive force primarily from a pre-existing bulk concentration difference between two electrolytes, whereas iontrovoltaic systems generate the relevant ionic chemical-potential asymmetry through dynamically differentiated interfacial EDL states even when the bulk liquid composition is nominally identical. Redox or corrosion reactions can coexist with and amplify iontrovoltaic conversion, as in RC-IVNGs, but they are treated as additional Faradaic contributions rather than the defining origin of the iontrovoltaic effect. Accordingly, control experiments under dark conditions, identical bulk electrolyte composition, reversed interfacial polarization/asymmetry, and reversible field modulation, together with operando characterization of EDL and SCR states, provide practical criteria for separating iontrovoltaic transduction from conventional electrochemical contributions.

Collectively, the evolution of S-L TENGs, TINGs, and IVNGs establishes a unified framework for dynamic EDL-enabled energy transduction at solid-liquid interfaces. As summarized in Table 1, these three systems exhibit distinct physical boundaries in terms of dominant interface, driving force, output mode, and characteristic electrical performance, while their representative voltage, current, power density, active area, operating conditions, and normalization methods also differ substantially. Therefore, the reported performance values should be interpreted within their respective experimental contexts rather than as directly comparable benchmarks. It should also be recognized that these three device categories are currently at different stages of development. S-L TENGs constitute a comparatively mature field that has been extensively investigated by many independent research groups, with their operation generally understood within the established framework of contact electrification and electrostatic induction, while wetting behavior, charge trapping, surface chemistry, and liquid composition can further modulate the interfacial charge dynamics and electrical output. In contrast, TINGs and IVNGs are more recently introduced concepts, and the literature explicitly adopting these device definitions and corresponding mechanistic frameworks remains comparatively limited. Their present interpretation therefore relies mainly on the initially demonstrated asymmetric-EDL-driven ionic transport and EDL-SCR-coupled ionic-electronic transduction, respectively, while related independent studies on nonequilibrium EDL regulation, concentration-gradient-driven ion migration, semiconductor-liquid charge redistribution, and interfacial ionic-electronic coupling provide important complementary physical context. Further independent validation across different materials, electrolytes, device architectures, and operating conditions will be important for establishing the generality and physical boundaries of these emerging mechanisms. Across these systems, interfacial EDLs evolve from passive charge-screening structures in S-L TENGs, to actively reconfigurable ionic transport media governed by asymmetric concentration gradients in TINGs, and ultimately to fully coupled ionic-electronic interfaces integrating semiconductor SCRs in IVNGs. This progression reflects a fundamental shift in the role of EDLs, from static electrostatic screening layers to dynamically programmable interfacial units capable of regulating charge generation, ionic migration, and carrier dynamics in a coordinated manner. Accordingly, the dominant energy-conversion mechanism transitions from electrostatic induction, to ion-driven transport, and finally to coupled ionic-electronic transduction under multiphysical-field regulation. Importantly, this evolution reveals that interfacial energy conversion is not governed by a single charge-carrier type, but emerges from hierarchical coupling among ionic distributions, interfacial electrostatics, and electronic band structures. Within this framework, dynamic EDLs serve as a unifying physicochemical platform linking mechanical stimuli, ionic transport, and electronic responses, thereby enabling the continuous transformation of environmental energy into electrical output.

Interfacial charge probing via S-L TENGs

Among the various information-transduction functions enabled by dynamic EDLs, interfacial charge probing represents one of the most direct routes for extracting physicochemical information from solid-liquid interfaces^[154-160]. In contrast to conventional electrochemical techniques that often require conductive substrates, external bias, or equilibrium conditions, triboelectrified interfaces intrinsically generate electrical signals that are directly coupled to interfacial charge transfer, ionic redistribution, and EDL evolution. As a result, triboelectric outputs can serve as sensitive, real-time fingerprints of interfacial processes, enabling operando monitoring of charge dynamics at solid-liquid interfaces. Over recent years, triboelectric probing has evolved from simple charge-transfer quantification to spatiotemporal charge imaging and, more recently, to chemical-information decoding, establishing a new paradigm for self-powered interfacial interrogation. An initial milestone was reported in 2021, when Zhang et al. developed a droplet-driven S-L TENG as a self-powered probe for interfacial charge-transfer analysis [Figure 15A(i)]^[161]. By using spatially separated electrodes beneath a dielectric substrate, the device enabled position-resolved monitoring of charge accumulation during droplet motion. The results revealed a continuous increase in transferred charge along the droplet trajectory, demonstrating that liquid-solid contact electrification is a progressive process rather than an instantaneous event [Figure 15A(ii)]. Systematic comparisons across aqueous, electrolyte, and organic systems further confirmed that electron transfer dominates interfacial charge generation, while dissolved ions primarily modulate the process through EDL formation and electrostatic screening [Figure 15A(iii)]. Beyond mechanistic insights, this platform also exhibited sensitivity to electrolyte concentration, solvent composition, and molecular interactions, highlighting its potential for self-powered interfacial-state sensing.

Figure 15. S-L TENGs-enabled interfacial information sensing via triboelectric charge probing. (A) Droplet-driven S-L TENG-based interfacial charge-transfer measurement at solid-liquid interfaces. Reprinted with permission from^[161] Copyright © 2021 American Chemical Society; (B) Spatiotemporal charge-transfer imaging using a pixeled S-L TENG array for real-time visualization of interfacial charge evolution. Reprinted with permission from^[162] Copyright © 2023 American Chemical Society; (C) Time-resolved charge-transfer mapping for chemical-information extraction, enabling operando monitoring of interfacial reactions and catalyst dynamics. Reprinted with permission from^[163] Copyright © 2026 WILEY‐VCH GmbH.

To further enhance spatial resolution, a pixeled S-L TENG array was subsequently developed for spatiotemporal mapping of interfacial charge evolution [Figure 15B(i)]^[162]. By integrating 432 independently addressable electrodes with 0.4 mm resolution, two-dimensional charge-transfer distributions during droplet motion could be directly reconstructed [Figure 15B(ii)]. The resulting charge maps revealed pronounced spatial heterogeneity in interfacial charge accumulation, providing experimental support for the coupled nature of electron transfer and ion-driven EDL screening. Importantly, the platform demonstrated the capability to encode both physical parameters (e.g., droplet velocity, light intensity) and chemical properties (e.g., pH), indicating that triboelectric charge patterns inherently contain multidimensional information [Figure 15B(iii)]. This marked a transition from scalar charge measurement to spatially resolved interfacial information imaging. Building on this concept, triboelectric charge mapping was further extended to operando chemical-information extraction [Figure 15C(i)]^[163]. By correlating dynamic charge-transfer patterns with interfacial chemical processes, the system enabled real-time monitoring of redox reactions, catalytic transformations, and molecular conversions. For example, oxidation of Fe²⁺ to Fe³⁺, enzymatic hydrolysis, and catalyst evolution processes each produced distinct charge-transfer signatures, allowing direct visualization of reaction kinetics and interfacial state evolution [Figure 15C(ii)]. These results demonstrate that triboelectric signals can serve not only as indicators of charge dynamics but also as encoded representations of underlying chemical processes. Collectively, these advances reveal a continuous evolution of dynamic EDLs from charge-transfer reporters to adaptive information-processing interfaces. By exploiting the coupled dynamics of ionic redistribution and charge transfer, dynamic EDLs provide an intrinsic mechanism for encoding and decoding interfacial physical and chemical states. In this context, S-L TENG-based triboelectric probing represents more than a self-powered sensing strategy; it establishes a general framework for operando interrogation of interfacial processes and the development of future electroionic information systems.

Operando EDL probing via S-L TENGs

Beyond interfacial charge probing, triboelectric outputs from S-L TENGs can be interpreted as real-time signatures of interfacial ionic redistribution and dynamic EDL evolution, enabling operando reconstruction of dielectric interfaces. Unlike conductive solid-liquid systems, where EDL structures can be readily characterized using conventional electrochemical techniques under applied bias and well-defined electrode configurations, dielectric solid-liquid interfaces represent a fundamentally more challenging regime for operando investigation. This limitation arises from the absence of intrinsic electronic conduction pathways in the dielectric solid phase, as well as the strongly coupled nature of interfacial charge generation, ionic redistribution, and electrostatic screening. Consequently, the formation and evolution of EDLs at dielectric interfaces cannot be directly accessed using traditional electrochemical or spectroscopic methods, leaving their dynamic behavior largely unresolved. Within this framework, a particularly insightful demonstration was reported in 2024 by Wei et al.^[69], who developed a single-electrode S-L TENG-based triboelectric probing platform to investigate the interfacial transition from ice-dielectric contact electrification to water-dielectric electrochemical interfaces. This approach enabled direct monitoring of the emergence, transformation, and evolution of interfacial EDLs during the solid-liquid phase transition.

To resolve the evolution pathway, the phase transition was divided into four representative stages: ice, initial melting, partial melting, and complete melting. During early melting, the emergence of microscale water regions increases effective contact area, leading to enhanced charge transfer and a peak output approximately six times higher than that of pure ice. As melting progresses, however, the increasing liquid fraction introduces ion-mediated screening, and the gradually forming EDL begins to attenuate interfacial charge accumulation. Upon complete melting, a stable solid-liquid interface with a fully developed EDL is established, resulting in a reduced but steady triboelectric output. The initial ice state is governed by electron-dominated solid-solid contact electrification. With partial melting, interfacial water introduces ions and initiates EDL formation, including the development of Stern and diffuse layers. Concurrently, the growing EDL progressively screens triboelectrically generated surface charges, leading to a competition between contact-area enhancement and electrostatic screening. At full melting, the system reaches a quasi-equilibrium EDL state, where charge generation and screening are balanced, producing stable triboelectric signals. Collectively, this work demonstrates that triboelectric outputs can serve as sensitive operando fingerprints of dynamic EDL evolution. More importantly, it establishes a unified picture linking phase transition, interfacial charge transfer, and EDL formation, providing a powerful platform for visualizing nonequilibrium interfacial electrochemical processes.

A further advance in dynamic EDL-enabled information sensing was achieved through the development of a triboelectric probing strategy capable of directly resolving electrolyte-dependent EDL structures at dielectric solid-liquid interfaces. Unlike previous studies focused primarily on charge-transfer processes or phase-transition-induced EDL evolution, this approach employs S-L TENGs as operando probes to establish a direct correlation between triboelectric outputs and interfacial ionic configurations, enabling quantitative visualization of EDL reconstruction under different electrolyte conditions. Wei et al. demonstrated that triboelectric signals encode electrolyte-dependent EDL configurations, transforming triboelectric measurements into a self-powered strategy for deciphering ion-specific interfacial organization^[164]. As illustrated in Figure 16A, a vertical contact-separation S-L TENG was utilized as a triboelectric charge-transfer probe. During repeated contact between a polytetrafluoroethylene (PTFE) dielectric surface and various electrolyte solutions, the transferred triboelectric charge was continuously recorded as a real-time indicator of interfacial charge distribution and EDL evolution. Three representative electrolyte systems were systematically investigated: symmetric electrolyte LiCl, large-anion asymmetric electrolyte Li[TFSI], and large-cation asymmetric electrolyte [EMIM]Cl. Owing to their distinct ionic sizes, mobilities, and interfacial affinities, these systems provide a model platform for elucidating ion-specific effects on EDL regulation at dielectric interfaces.

Figure 16. Dynamic EDL probing reveals electrolyte-dependent interfacial ionic structures at dielectric solid-liquid interfaces developed by Wei et al. in 2025. Reprinted with permission from^[164] Copyright © 2025 Springer Nature. (A) S-L TENG-based triboelectric charge-transfer probing platform for operando characterization of EDLs formed in different electrolyte environments at dielectric solid-liquid interfaces; (B) Evolution of triboelectric signals with increasing electrolyte concentration for LiCl, Li[TFSI], and [EMIM]Cl, revealing distinct pathways of EDL reconstruction and interfacial charge regulation; (C-E) Proposed models of electrolyte-dependent EDL evolution, showing EDL compression in LiCl and charge inversion induced by ion-specific adsorption and mobility asymmetry in concentrated Li[TFSI] and [EMIM]Cl electrolytes.

The concentration-dependent triboelectric responses are summarized in Figure 16B. For LiCl solutions, the Q_SC monotonically decreases with increasing concentration while maintaining constant polarity [Figure 16B(i)], indicating progressive EDL compression and enhanced electrostatic screening under increasing ionic strength^[164]. In contrast, both Li[TFSI] and [EMIM]Cl exhibit pronounced polarity inversion at high concentrations [Figure 16B(ii and iii)]. While their lower-concentration behavior resembles that of LiCl, a critical concentration (~10^-1 M) triggers a transition from monotonic attenuation to charge inversion, indicating a fundamental reconstruction of interfacial charge distribution and EDL structure in concentrated asymmetric electrolytes. To rationalize these behaviors, concentration-dependent EDL evolution models were proposed [Figure 16C]. For LiCl [Figure 16C(i and ii)], the EDL follows a classical two-step structure composed of an IHP, OHP, and diffuse layer. Increasing ionic strength compresses the diffuse layer and strengthens charge screening, but the overall charge polarity remains unchanged. For Li[TFSI] [Figure 16D(i and ii)], the large steric size and reduced mobility of [TFSI]^- anions suppress their participation in interfacial screening, while Li⁺ ions preferentially accumulate near the interface^[164]. At high concentrations, excessive cation accumulation leads to overcompensation of surface charge, resulting in EDL reconstruction and charge inversion driven by mobility asymmetry. For [EMIM]Cl [Figure 16E(i and ii)], EDL inversion originates from strong interfacial adsorption of hydrophobic [EMIM]⁺ cations, which dominate the OHP at elevated concentrations and induce positive charge overcompensation. In this case, charge inversion is governed primarily by ion-specific adsorption rather than transport asymmetry. These results demonstrate that triboelectric outputs can serve as highly sensitive operando fingerprints of electrolyte-dependent EDL reconstruction. More importantly, S-L TENG-based probing provides a direct experimental route to resolve ion-specific effects in dielectric interfacial electrochemistry, revealing how ionic size, mobility, and interfacial affinity collectively govern EDL structure and its dynamic evolution.

Collectively, these two representative studies establish S-L TENGs as a universal operando platform for probing EDLs at dielectric solid-liquid interfaces. By converting interfacial charge-transfer processes into measurable electrical signals, this strategy enables real-time visualization of both phase-transition-induced EDL evolution and electrolyte-dependent EDL reconstruction. Importantly, these results demonstrate that triboelectric outputs are not only sensitive to interfacial charge generation but also encode the structural dynamics of ion distributions within EDLs. Therefore, S-L TENGs provide a unified experimental framework for decoding dielectric interfacial electrostatics under nonequilibrium conditions, bridging charge transfer, ionic organization, and EDL formation within a single operando sensing paradigm.

Interfacial information sensing via S-L TENGs

Dynamic EDLs not only serve as sensitive probes of interfacial physicochemical processes but also function as intrinsic transducers that convert external stimuli into measurable electrical signals. As evidenced by operando studies of phase transitions and electrolyte-dependent EDL reconstruction, variations in temperature, ionic composition, molecular adsorption, and interfacial states continuously regulate EDL structures and modulate interfacial charge-transfer behavior. Consequently, the electrical outputs of S-L TENGs are inherently governed by dynamic EDL evolution, effectively encoding rich information about the surrounding environment. Building upon this principle, dynamic EDLs have emerged as universal interfacial information-encoding media, enabling liquid identification, thermal sensing, chemical monitoring, and physiological signal detection in self-powered environmental and biomedical systems^[165-169]. One of the earliest demonstrations of dynamic EDL-enabled environmental recognition was reported in 2023 by Wei et al., who developed a self-powered triboelectric taste-sensing platform based on the S-L TENG^[170]. Different liquids exhibit distinct ionic compositions, polarities, viscosities, and interfacial affinities, leading to characteristic EDL configurations and charge-transfer behaviors during solid-liquid contact electrification. These differences generate unique triboelectric signal patterns, which can be decoded as electrical fingerprints for liquid identification. Coupled with machine-learning analysis, the system achieved recognition accuracies exceeding 91%, demonstrating that dynamic EDLs can effectively encode complex physicochemical information into electrical signals. Beyond liquid identification, dynamic EDLs are also highly sensitive to thermal stimuli. In 2022, Feng et al. reported a thermoresponsive S-L TENG based on a temperature-responsive copolymer [Figure 17A(i)]^[171]. The temperature-induced conformational transition near the lower critical solution temperature modulates interfacial hydration structure, wettability, and EDL configuration. These coupled variations significantly alter interfacial charge transfer, resulting in a ~27-fold increase in output current from 20 to 60 °C [Figure 17A(ii)]. This result demonstrates that dynamic EDLs can efficiently transduce thermal signals into electrical outputs through temperature-dependent interfacial ionic reorganization.

Figure 17. Dynamic EDL-enabled environmental and physiological sensing via S-L TENGs. (A) Temperature sensing enabled by thermally regulated interfacial hydration structures and dynamic EDL evolution, developed by Feng et al. in 2022. Reprinted with permission from^[171] Copyright © 2022 WILEY‐VCH GmbH; (B) Chemical-information sensing through ion- and contaminant-induced EDL reconstruction at solid-liquid interfaces, developed by Kaswan et al. in 2025. Reprinted with permission from^[172] Copyright © 2025 WILEY-VCH GmbH; (C) Physiological-information sensing through sweat-ion-mediated modulation of interfacial EDLs and triboelectric outputs in wearable systems, developed by Li et al. in 2025. Reprinted with permission from^[173] Copyright © 2025 WILEY-VCH GmbH.

Dynamic EDLs can further encode chemical information in aqueous environments. In 2021, Kaswan et al. developed a droplet-based triboelectric nanosensor integrated with molecular recognition interfaces for chemical sensing [Figure 17B(i)]^[172]. Selective adsorption of target ions or molecules continuously reconstructs interfacial charge distributions and EDL structures, producing measurable changes in triboelectric outputs [Figure 17B(ii)]. The platform enabled sensitive detection of heavy-metal ions below regulatory thresholds and extended to biological species monitoring through adsorption-induced interfacial modulation [Figure 17B(iii)]. These findings establish that dynamic EDLs can transduce subtle chemical variations into electrical signals, enabling self-powered water-quality and biochemical sensing. More recently, dynamic EDL-enabled sensing has been extended from environmental monitoring to physiological signal detection in wearable systems. In 2024, Li et al. developed a bioinspired heterogeneous-wettability TENG for sweat analysis [Figure 17C(i)]^[173]. Driven by wettability-gradient-induced transport and capillary pressure, sweat ions are continuously enriched at the interface, dynamically modulating EDL structures and enhancing triboelectric outputs. The device exhibited a V_OC increase from 82 to 148 V with rising electrolyte concentration [Figure 17C(ii)] and achieved a signal-to-noise ratio of 51 dB. By integrating ion-selective membranes, selective detection of Na⁺, K⁺, and Ca²⁺ ions was further realized, enabling real-time physiological monitoring [Figure 17C(iii)]. This work highlights the potential of dynamic EDLs as a bridge between interfacial electrochemistry and wearable biosensing, opening new opportunities for self-powered health monitoring systems. These studies demonstrate that dynamic EDLs provide a universal interfacial mechanism for encoding environmental and physiological information into electrical signals via S-L TENGs. By coupling interfacial ionic redistribution with charge-transfer processes, diverse external stimuli, including chemical composition, temperature, molecular adsorption, and biological ion flux, can be effectively transduced into distinct triboelectric signatures. This establishes dynamic EDLs as a general information-encoding platform for self-powered sensing systems, bridging interfacial electrochemistry with environmental monitoring and wearable bioelectronics.

Bionic logic control via TINGs

S-L TENGs establish dynamic EDLs as interfacial information-encoding media for sensing external physicochemical stimuli, and further TINGs extend this functionality from signal generation to ionic information transmission and processing. This transition relies on the programmable regulation of ionic distributions, polarity, and transport direction within dynamic EDLs. In biological nervous systems, information is encoded and transmitted through dynamic ionic concentration gradients and membrane-potential variations across cell membranes. Inspired by this principle, triboiontronics explores whether dynamic EDLs at solid-liquid interfaces can function as programmable ionic-information carriers rather than merely as energy-conversion or sensing interfaces. A pioneering advance was reported by Li et al. in 2023, who demonstrated dynamic regulation of EDL charge distributions through triboelectrically induced ion polarization^[57]. Triboiontronic systems use triboelectrically generated electrostatic fields to actively regulate ionic distributions within both the Stern layer and diffuse layer. Through this process, ionic polarity, ionic concentration, and ionic transport direction can be dynamically programmed, enabling bidirectional ionic-electronic signal conversion and establishing dynamic EDLs as functional units for ionic information transmission and logic regulation.

To demonstrate this concept, a triboiontronic bionic neurologic circuit was constructed for bidirectional ionic-electronic signal conversion. In the initial state, the naturally formed EDL generated only weak ionic signals because of the limited charge density within the diffuse layer. When positively charged fur contacted the PET substrate, triboelectric polarization enhanced the negative charge density within the Stern layer, inducing cation enrichment in the diffuse layer and generating positive ionic signals. These ionic signals were subsequently converted into forward electronic currents through interfacial ionic-electronic coupling. After removal of the fur, residual negative triboelectric charges on the PET surface reversed the interfacial ionic distribution, promoting anion enrichment and producing negative ionic signals, which generated reverse electronic currents in the external circuit. Through reversible switching among these EDL states, physical contact events were encoded into ionic polarity states and further converted into corresponding electronic outputs without an external power supply. As a proof-of-concept demonstration, the triboiontronic neurologic circuit was used to regulate the rhythmic motion of a virtual robot. This work demonstrated that dynamic EDLs can function not only as ionic-information carriers but also as active information-processing interfaces capable of implementing neuromimetic signal transmission, polarity regulation, and logic control.

Beyond ionic signal polarity regulation, dynamic EDLs can also control the transport behavior of charged liquid carriers, enabling programmable logic control. In 2025, Li et al. developed a triboelectric-programmed droplet manipulation strategy based on dynamic EDL regulation and triboelectric wetting^[70]. In this system, the triboelectric charge polarity carried by droplets was programmed by tailoring ionic distributions within the solid-liquid interfacial EDLs, allowing droplet motion to be controlled by external triboelectric fields. To reveal the role of dynamic EDLs in droplet information regulation, the authors investigated the influence of ionic species and concentration on droplet triboelectric charging. For conventional LiCl solutions, droplets remained positively charged over a broad concentration range after contact electrification with PTFE. In contrast, [EMIM]Cl droplets exhibited a concentration-dependent polarity transition. At low concentrations, they behaved similarly to LiCl droplets and carried positive charges. At higher concentrations, however, the droplet polarity gradually reversed and became negative. This polarity inversion originates from concentration-dependent EDL reconstruction, where asymmetric ionic packing and interfacial adsorption alter the dominant charge-transfer pathway during solid-liquid contact electrification. Based on this mechanism, droplets with different programmed charge polarities exhibited opposite transport behaviors under the same triboelectric field. Positively charged droplets were attracted toward negatively charged field regions, whereas negatively charged droplets were repelled and transported in the opposite direction. Because droplet polarity was determined by the underlying EDL structure, dynamic EDL regulation effectively translated interfacial ionic information into programmable droplet trajectories. The system achieved ultrafast droplet transport velocities approaching 450 mm s^-1 on common dielectric surfaces without chemical surface modification, demonstrating efficient EDL-mediated control of ionic carriers. More importantly, this EDL-programmed droplet transport enabled ionic logic functions. By arranging positive and negative triboelectric-field regions along the transport pathway, droplets with different charge polarities could be selectively routed toward distinct output terminals. Through this process, ionic information encoded in EDL structures was converted into droplet-motion pathways and then translated into distinct electrical outputs. The resulting system further demonstrated robotic motion control without external power supplies or complex electronic circuits.

Collectively, these studies establish TINGs as dynamic EDL-enabled platforms for ionic information transmission and bionic logic control. Compared with S-L TENG-based information sensing, where EDL evolution is mainly used to encode external stimuli into electrical fingerprints, TING-based information systems actively manipulate ionic polarity, ionic flux, and ionic carrier transport pathways. This transition extends the role of dynamic EDLs from passive information encoding to programmable information routing and logic execution. Dynamic EDLs therefore evolve into active ionic-information-processing units, providing a promising route toward autonomous iontronic logic systems and embodied ionic intelligence.

Information transmission via TINGs

Dynamic EDLs can regulate ionic polarity and support logic operations at individual solid-liquid interfaces, and further extending such local ionic signaling into efficient long-range information transmission remains a major challenge. In biological nervous systems, ionic concentration gradients across cell membranes not only encode information but also support signal propagation over macroscopic distances through coordinated ionic transport and continuous maintenance of nonequilibrium electrochemical states. Inspired by this principle, Li et al. demonstrated in 2025 that dynamically regulated asymmetric EDLs can function not only as local ionic-information-processing interfaces but also as long-range ionic-information transmission channels, thereby enabling wireless underwater communication through coupled triboiontronic interfaces^[93]. Building upon the asymmetric EDL-driven ionic migration mechanism of TINGs, a wireless underwater triboiontronic communication platform was developed. In this system, periodic contact-separation motion at the transmitting interface generated time-dependent ionic pulses through the dynamic formation and reconstruction of asymmetric EDLs. These ionic pulses propagated through the aqueous medium and were subsequently converted into electrical signals at the receiving terminal through interfacial ionic-electronic coupling. In this way, mechanical stimuli were encoded into ionic fluxes and transmitted underwater without relying on conventional acoustic, optical, or electromagnetic communication modes.

To evaluate the capability for long-distance ionic-information transmission, the distance between two coupled Au/FEP-liquid interfaces was systematically varied in different aqueous environments. Benefiting from triboelectrically enhanced asymmetric EDLs, stable ionic communication was achieved over distances of up to 30 cm, despite each triboiontronic unit having an active area of only 1 cm². Reliable signal transmission was observed in deionized water, tap water, artificial seawater, and saturated MgCl₂ solution, with I_SC of approximately 20, 40, 110, and 420 μA, respectively. These results indicate that increasing ionic conductivity and carrier concentration substantially promotes directional ionic migration and enhances long-range communication performance. More importantly, the realization of centimeter-scale signal propagation demonstrates that dynamic EDL coupling can effectively overcome the spatial confinement of individual interfacial EDLs. The received electrical pulses were further decoded using an ASCII-based encoding protocol to reconstruct character information. To improve communication reliability and suppress environmental interference, the initial pulses were designed as a judgment region, where the characteristic attenuation behavior of triboiontronic signals was used to identify the information source, while the subsequent pulses constituted the information region encoding the message. Using this strategy, the character sequence “OK” was successfully transmitted and decoded underwater. Collectively, this work demonstrates that dynamically evolving asymmetric EDLs can serve not only as ionic transport pathways but also as active ionic-information carriers capable of encoding, transmitting, and regenerating signals over macroscopic distances. More fundamentally, it reveals that dynamic EDLs are not restricted to localized interfacial charge regulation; through coupled asymmetric EDL construction and triboelectrically induced ion polarization, they can be extended into long-range iontronic communication channels. This advance marks an important transition from ionic information encoding and local logic regulation toward distributed ionic communication networks, opening new opportunities for underwater communication, large-scale iontronic systems, and future iontronic embodied intelligence^[174].

Light-gated iontronic computing via IVNGs

Dynamic EDLs in S-L TENGs and TINGs enable information acquisition and ionic information transmission, respectively, and their functionality can be further extended toward iontronic computing through dynamic EDL-SCR coupling in IVNGs. This transition is critical because iontronic computing enables dynamic EDL systems to move beyond sensing and communication toward active information processing, providing a key step toward energy-information-integrated iontronic intelligence^[48,175-181]. By introducing semiconductor carrier dynamics into iontronic systems, IVNGs provide an additional degree of freedom for regulating ionic information states. This enables programmable iontronic computing through cooperative interactions among photocarrier excitation, interfacial electrochemical reactions, SCR modulation, and asymmetric EDL-mediated ionic transport. A representative example was recently demonstrated by Li et al., who developed a light-gated iontronic computing architecture based on RC-IVNGs [Figure 18]^[94]. Owing to the strong coupling among photocarrier generation, interfacial oxidation, and dynamic EDL-SCR interactions, the RC-IVNG exhibited two stable and distinguishable ionic-current states under different illumination conditions. In the absence of UV irradiation, the device remained in a low-current state. Under UV illumination, photogenerated carriers were separated by the coupled EDL-SCR electric field, while interfacial oxidation reactions generated additional ionic species and reinforced EDL asymmetry, resulting in a significantly enhanced ionic current [Figure 18A]. These reproducible current states provide a robust physical basis for optically encoded iontronic information. As a result, the ionic transport state of the device can be programmably switched between different information states through external optical inputs.

Figure 18. Light-gated iontronic computing enabled by dynamic EDL-SCR coupling in RC-IVNGs, developed by Li et al. in 2026. Reprinted with permission from^[94] Copyright © 2026 Springer Nature. (A) Optical encoding of binary iontronic information states through illumination-controlled ionic-current outputs in RC-IVNG units; (B) Construction of a light-gated iontronic computing architecture using independently addressable RC-IVNG input nodes; (C-F) Realization of representative Boolean logic functions, including OR, AND, NOR, and NAND operations, through optically regulated ionic transport and dynamic EDL-SCR interactions.

Based on this principle, two RC-IVNG units were employed as independently addressable input nodes, where the illumination-off and illumination-on states were assigned as logical “0” and “1”, respectively. Because each RC-IVNG generated distinct ionic-current outputs under different optical conditions, the resulting ionic signals could be combined and processed through specific coupling configurations [Figure 18B]. By defining appropriate output-current thresholds, representative Boolean logic functions, including OR, AND, NOR, and NAND operations, were successfully realized [Figure 18C-F]. Importantly, these operations were achieved directly through optically regulated ionic transport without relying on transistors, external bias voltages, or conventional electronic logic components. More significantly, the logical behavior of RC-IVNGs originates from intrinsic matter-energy-information coupling at semiconductor-liquid interfaces. Ionic species act as physical information carriers, optical excitation serves as a programmable energy input, semiconductor carrier dynamics regulate interfacial electronic states, and dynamic EDL-SCR coupling governs the evolution of ionic information states. Within this framework, information encoding, signal modulation, and logic computation are integrated within a single interfacial iontronic system. IVNG-based light-gated computing demonstrates that dynamic EDLs can evolve beyond sensing interfaces and ionic communication channels into active computational units capable of regulating ionic fluxes and processing information. By integrating photonic stimulation, semiconductor carrier dynamics, ionic transport, and Boolean logic operations, IVNGs establish a new paradigm for light-gated iontronic information processing.

Collectively, S-L TENGs, TINGs, and IVNGs reveal a continuous evolution of dynamic EDLs from interfacial information-encoding media to programmable ionic-information channels and ionic-electronic computational units. In S-L TENGs, dynamic EDLs encode external stimuli into triboelectric fingerprints; in TINGs, asymmetric EDLs enable bionic logic control and long-range iontronic communication; and in IVNGs, EDL-SCR coupling integrates semiconductor carrier dynamics to realize light-gated iontronic computing. This progression establishes dynamic EDLs as a unified physicochemical platform for sensing, communication, and computation at solid-liquid interfaces, providing an essential foundation for self-powered iontronic intelligence and matter-energy-information integrated systems. In terms of experimental evidence, the mechanisms discussed above can be distinguished according to the nature and extent of their validation. For S-L TENGs, contact electrification and electrostatic induction constitute the well-established operating framework, with interfacial ionic screening and EDL evolution extensively supported across diverse solid-liquid systems. For TINGs, asymmetric-EDL-driven directional ionic transport has been experimentally validated through controlled interfacial asymmetry, polarity-dependent responses, wetting-sequence regulation, and corresponding ionic-transport behavior. For IVNGs, dynamic EDL-SCR coupling has been supported by complementary measurements of local ionic redistribution, semiconductor surface potential and work function, flat-band potential, and electrical output under controlled interfacial regulation. These results provide strong experimental support for the proposed TING and IVNG mechanisms, while continued studies across broader material and device systems will further expand their general applicability. In contrast, large-scale adaptive iontronic networks and iontronic embodied intelligence remain prospective directions rather than experimentally established capabilities.