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Kinetic analysis of liquid–solid contact electrification: Using adsorption models as mechanistic probes for hybrid EDL behavior
(2026-08-01)
Chaithaweep, Kanokwan
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Pharino, Utchawadee
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Pongampai, Satana
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Sriphan, Saichon
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Charoonsuk, Thitirat
Liquid–solid interfaces are central to technologies ranging from energy storage to triboelectric nanogenerators (TENGs). Whereas classical electric double layer (EDL) theory describes these interfaces mainly in terms of electrostatic ion adsorption, hybrid EDL concepts suggest that interfacial electron transfer may also contribute importantly to charge generation. However, the hybrid EDL model has so far been discussed primarily at a qualitative level or through complex theoretical and computational treatments, and a simple, experimentally accessible macroscopic kinetic handle that can discriminate, in operando, between adsorption‑dominated and ET‑influenced regimes remains lacking. By analyzing high-resolution charging dynamics over systematically varied H₂SO₄ and HNO₃ concentrations, a clear concentration-dependent kinetic transition is identified. At low ionic strengths, the charging process is described more effectively by pseudo-second-order (PSO) kinetics, consistent with a reaction-influenced interfacial step, whereas at higher concentrations the system becomes pseudo-first-order (PFO) dominated, consistent with transport- and ion-screening-controlled behavior. Although previous studies have provided compelling theoretical and spectroscopic evidence that interfacial electron transfer contributes to liquid–solid contact electrification in TENGs, these mechanisms have rarely been examined through such simple macroscopic kinetic formalisms. In this work, classical adsorption kinetic models are used as operational probes for distinguishing electron-transfer-influenced regimes from ion-transport-dominated regimes at PTFE/liquid interfaces. The PSO-to-PFO crossover reported here is interpreted within the hybrid EDL framework as a kinetic marker of a transition from an electron-transfer-influenced charging regime at low concentration to an ion-transport- and screening-dominated regime at high concentration, thereby demonstrating how adsorption kinetics can serve as a practical diagnostic language for liquid–solid triboelectric systems.
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Harvesting energy from friction: the revolutionary decade of triboelectric nanogenerators
(2026-04-01)
Khanapurarm, Uday Kumar
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Rani, Gokana Mohana
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Panda, Swati
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Charoonsuk, Thitirat
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Mistewicz, Krystian
Triboelectric nanogenerators (TENGs) have rapidly developed into a transformative energy harvesting technology, enabling self-powered, sustainable electronic systems. This review offers the first comprehensive, multidisciplinary perspective that connects the physics of triboelectric charge transfer with material innovation, device engineering, and real-world applications. We systematically categorize and measure the triboelectric series across a wide range of materials, including polymers, 2D materials, MOFs, perovskites, cellulose, and biodegradable frameworks, using experimentally validated methods. In addition to traditional approaches, this work highlights emerging strategies such as machine learning-guided material discovery, 3D printing, and advanced structural engineering to improve charge retention, durability, and power output. Unlike existing reviews, it uniquely combines theory and application insights, presents diverse uses from biomedical sensing and environmental monitoring to underwater communication and mechanoluminescence, and outlines a forward-looking plan for sustainable energy harvesting. This comprehensive synthesis serves as an essential resource for researchers and technologists designing next-generation TENGs and multifunctional self-powered devices.
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Complex Impedance Formalism for Probing Dehydration, Dehydroxylation, and Rehydroxylation Dynamics of UiO-66-Based Metal–Organic Frameworks
(2026-02-12)
Maluangnont, Tosapol
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Chaithaweep, Kanokwan
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Sriphan, Saichon
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Meejaiyen, Parinya
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Anutrasakda, Wipark
It is known that the UiO-66 metal–organic framework (MOF) undergoes dehydration of physisorbed water and dehydroxylation of the zirconium clusters from RT to ∼300 °C, while the porous structure remains intact. These two processes are typically studied by thermogravimetric analysis and its derivative method (TGA/DTG), as well as differential scanning calorimetry (DSC). Here, we probe the same phenomena using temperature-dependent complex impedance spectroscopy. Peaks observed in the AC conductivity and in the real and imaginary parts of the dielectric permittivity (σ<inf>AC</inf>, ε′, and ε″) are due to thermally accelerated proton (Grotthuss) hopping competing with the loss of proton carriers during guest removal and dehydroxylation up to 350 °C. Meanwhile, peaks in the loss tangent (tan δ) and phase shift (Θ) identify the temperature at which dielectric-to-heat conversion is maximized. Additionally, peaks in the imaginary part of the impedance (−Z″) and in the real part of the electric modulus (M′) mark the temperature at which the material exhibits its highest insulating character. The MOFs examined include UiO-66 with the 1,4-benzenedicarboxylate linker and UiO-66-Py with the 2,5-pyridinedicarboxylate linker, the latter further modified through trifluoroacetic acid modulation, 1-bromopropane functionalization, and optional intermediate heat treatment. Impedance measurements under cooling reveal composition-dependent rehydroxylation behavior, with the conductivity recovery as early as at 250 °C in some Py-based derivatives vs flat response in pristine UiO-66. Overall, our work provides a comprehensive analysis of several complex electrical quantities and their physical interpretation, offering complementary insights into the dehydration, dehydroxylation, and rehydroxylation dynamics of UiO-66-based MOFs.
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Application of Heywang model to the apparent PTCR effect in water-adsorbing layered materials
(2026-01-01)
Pulphol, Phieraya
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Sriphan, Saichon
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Chaithaweep, Kanokwan
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Vittayakorn, Naratip
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Maluangnont, Tosapol
Surface proton/hydroxide conduction predominates at ambient conditions prior to levelling off at elevated temperatures due to water evaporation and subsequent loss of charge carriers. This water-induced charge transport results in the “apparent” positive temperature coefficient of resistivity (PTCR) effect. Herein, we show that Heywang model typical of classical ferroelectric PTCR ceramics is applicable to a wide range of water-adsorbing layered materials (0.17–4.76 wt% H<inf>2</inf>O). Several examples include layered alkali titanates with negatively-charge sheets; one van der Waals material (g‒C<inf>3</inf>N<inf>4</inf>) with neutral sheets; and a NiFe layered double hydroxide with positively-charge sheets. The linear log ρ<inf>DC</inf> vs (ε′<inf>DC</inf>T)-1 plots (ρ<inf>DC</inf> = static resistivity, ε′<inf>DC</inf> = static dielectric permittivity, and T temperature) are observed from 25 to 250 °C where resistivity and dielectric permittivity varied up to five orders of magnitude. Using Cs<inf>2</inf>Ti<inf>6</inf>O<inf>13</inf> as a representative sample, the density of acceptor states at the grain boundary N<inf>s</inf> (the exact nature to be elucidated) is ∼1010-1011 cm-2, slightly dependent on the heating/cooling rates (0.5, 2 and 5 °C·min-1). Complex plane analyses show that capacitances at grain/grain boundaries alike are constant regardless of temperatures, but resistances in both cases peak at 150–200 °C. While rigorous theoretical basis is yet to be constructed, the observed linearity suggests that there could be a common foundation between these two classes of PTCR materials which have been treated separately so far.
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Flexible and Self-Powered Wearable Sensors for Tremor Monitoring in Parkinson'S Disease: Recent Advances in Materials and Device Architectures
(2026-01-01)
Ukasi, Sirinya
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Hajra, Sugato
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Kim, Hoe Joon
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Sriphan, Saichon
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Pongampai, Satana
Parkinson's disease (PD) is a progressive neurodegenerative disorder where tremor remains one of the most prominent and disabling motor symptoms. Traditional clinical rating scales for disease severity rely on clinician observation and patient self-report, often failing to capture the dynamic and continuous nature of tremors in daily life. This drives the development of objective monitoring technologies, such as wearable sensors, for more accurate evaluation of PD severity. However, many existing systems use rigid materials that lack the mechanical compliance and skin conformability required for stable biointegration. This review summarizes advances in flexible wearable sensors for PD tremor assessment from material innovations to a device engineering perspective, covering inertial measurement units (IMUs), electromyography (EMG), and emerging self-powered systems such as triboelectric (TENG) and piezoelectric nanogenerators (PENG). This review highlightshow functional materials, microstructural design, and device architectures govern sensing mechanisms and performance, with particular emphasis on the transition from rigid components to soft, skin-interfaced technologies. Recent patent activity reflects a shift toward multimodal, wireless, and clinically integrated platforms. Despite progress, challenges remain, including motion artifacts, durability, and limited large-scale clinical validation. Integration of flexible materials, self-powered designs, and AI-driven analytics enables continuous, personalized monitoring, moving closer to real-world clinical deployment and improved patient care.
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A Self-Powered and Chemically Responsive Triboelectric Nanogenerator Based on Surface Protonation in SrO2Nanopowder/Graphene Oxide/epoxy Composite for pH Sensing
(2025-12-05)
Saengpoe, Prasert
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Supasai, Wisut
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Amorntep, Narong
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Nilnumpetch, Chatree
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Nokkaew, Manussawee
Practical implementation of triboelectric nanogenerators (TENGs) in autonomous systems is frequently impeded by their inadequate durability in chemically harsh environments. To address this limitation, we present a durable TENG utilizing a strontium dioxide nanopowders/graphene oxide/epoxy resin (SrO<inf>2</inf>NPOs/GO/ER) composite, positioning SrO<inf>2</inf>NPOs as an innovative, high-permittivity filler for triboelectric applications. By synergistically integrating the elevated dielectric constant of SrO<inf>2</inf>NPOs with the interfacial polarization of GO NPOs, our optimized composite achieves an outstanding output of approximately 136 V and 2.3 μA/cm2under a 100 N force, exceeding the performance of numerous advanced TENGs. Significantly, we convert a common degradation mechanism, i.e., surface protonation, into a functional sensing approach. The device leverages reversible protonation–deprotonation dynamics to convert environmental pH into distinct electrical signals, enabling self-powered, real-time pH sensing. The sensor exhibits excellent linearity (R2> 0.97) across three distinct operational regions (pH 1–12), demonstrating high sensitivity to acidity changes. The device has demonstrated remarkable durability, completing approximately 11,000 mechanical cycles. Also, the proposed device serves high chemical durability, maintaining stable performance (up to 6000 cycles) after 24 h immersion in neutral and alkaline solutions. Our work establishes a resilient, multifunctional platform that simultaneously harvests energy and senses its chemical surroundings by reframing protonation as a design principle. This breakthrough paves the way for next-generation TENGs for use in environmental monitoring, resilient IoT networks, and adaptive self-powered electronics that can function under conditions where the chemical environment changes.
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Hybrid Textile Nanogenerators Based on Cotton-PANI/CNT Composites for Simultaneous Harvesting of Mechanical and Thermal Energy
(2025-06-09)
Navatragulpisit, Suchanat
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Saetang, Chanachot
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Mohsom, Phitchayaphorn
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Sriphan, Saichon
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Pakawanit, Phakkhananan
Rapid advancements in wearable electronics (WEs) have accelerated the development of textile-based triboelectric nanogenerators (T-TENGs) as flexible and sustainable power sources. However, one major challenge lies in mitigating the charge loss due to heat generation during repeated mechanical operations. In this work, we demonstrate a hybrid energy-harvesting textile that integrates both triboelectric and thermoelectric functionalities. Cotton (cot-) fabric serves as the triboelectric substrate, coated with a polyaniline/carbon nanotube (PANI/CNT) thermoelectric composite, enabling the simultaneous harvesting of mechanical and thermal energy. The optimized cot-PANI/CNT device exhibits a high Seebeck coefficient (98.5 mV/K), a power factor of ∼9 μW/mK2, and improved electrical conductivity, while maintaining fabric flexibility. The hybrid system achieves an open-circuit voltage (V<inf>OC</inf>) of ∼40.0 V and a short-circuit current (I<inf>SC</inf>) of ∼77.3 μA, yielding a maximum output power of ∼272.3 μW (30.3 μW/cm2). The device successfully powers wearable-scale electronics, and mechanistic insights are provided into the synergistic charge generation pathways between the triboelectric and thermoelectric components.
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AC Electrical Properties of a NiFe-Layered Double Hydroxide with an Exceptionally Low Charge Density
(2025-05-08)
Maluangnont, Tosapol
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Sriphan, Saichon
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Chaithaweep, Kanokwan
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Vittayakorn, Naratip
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Wijitwongwan, Rattanawadee Ploy
Single-phase NiFe-layered double hydroxides (LDHs) with low and high charge densities [CD, 0.85 vs 3.23 nm-2; FeIII/(NiII + FeIII) = 0.05 and 0.25] were successfully prepared via urea-assisted coprecipitation in aqueous glycerol under hydrothermal conditions. The low-CD NiFe-LDH showed decreased apparent activation energies of water evaporation and of glycerol thermal decomposition, suggesting diminished intercalate/layer interactions relative to the high-CD one. The alternating current properties of the two samples were investigated on frequency and temperature domains by several formalisms that highlight distinct electrical components. We found that the low-CD NiFe-LDH exhibited smaller static dielectric permittivity and slower relaxation time, and it was less conducting than the high-CD analog. Complex plane analyses revealed the temperature dependence of resistance and capacitance at grain and grain boundary, varying by 7-10 orders of magnitude due to water loss and glycerol loss (∼9.5 and 11.3 wt %, respectively). Our work provides insights into intercalate dynamics in a low charge density LDH, which is difficult to obtain so far, from ambient to elevated temperatures (RT-250 °C) prior to decarbonation and layer collapse.
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High-Performance Droplet-Based Triboelectric Nanogenerators: A Comparison of Device Configuration and Operating Parameters
(2025-05-06)
Chaithaweep, Kanokwan
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Pharino, Utchawadee
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Pongampai, Satana
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Hajra, Sugato
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Kim, Hoe Joon
Droplet-based electricity generators (DEGs) harness liquid-solid electrification to convert water droplets impacts into electrical energy. This study systematically examines how droplet height, droplet volume, flow rate, and substrate tilt angle influence DEG performance using polytetrafluoroethylene (PTFE) as a triboelectric layer and deionized water. Three electrode designs (double, top, bottom) are evaluated, revealing that the double-electrode configuration delivers the highest output. This enhanced performance arises from synergistic droplet motion, electrical double-layer formation, and charge discharge, as validated by an equivalent circuit model. By varying droplet heights from 1–20 cm, volumes of 7.7–50 µL, flow rates of 50–300 drops/min, and tilt angles of 0–90°, an optimized setup yields −70 V and 22 mA, translating to a power density of 0.28 µW cm−2. High-speed imaging correlates these outputs with droplet impact dynamics and the resulting charge transfer. Additionally, the optimized DEG can power small electronic devices, charge capacitors, and monitor artificial acid rain in real-time, displaying distinct electrical signals compared to typical rainwater. These findings underscore the potential of DEGs as renewable energy harvesters and smart environmental sensors, paving the way for advanced on-demand power generation in diverse settings.
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A highly sensitive disease pre-screening approach for glycosuria: Triboelectric sensing at the liquid-solid interface
(2025-03-15)
Pharino, Utchawadee
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Chaithaweep, Kanokwan
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Pongampai, Satana
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Chanlek, Narong
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Kothan, Suchart
Prescreening and disease detection offer significant benefits in the prevention of serious illnesses. Traditional screening methods for disease identification have been complex and expensive, often requiring invasive procedures, which can be both harmful and uncomfortable. To address these limitations, various non-invasive screening technologies have been developed. Among recent innovations, the liquid–solid interface concept has emerged as a promising avenue for nanogenerator applications, enabling the harvesting and sensing of liquid energy and substances. In this study, we introduce a liquid–solid interface triboelectric sensor (LS-TES) for non-invasive disease screening and sensing. The LS-TES, utilizing a double-electrode configuration, delivers an immediate electrical response upon droplet contact with the solid surface and top electrode. In the case of urine glucose monitoring, our findings demonstrate a significant reduction in electrical signals with increasing concentrations of glucose, as glucose molecules hinder electron transfer from water to the solid surface, thereby disrupting the formation of the electrical double layer at the liquid–solid interface. The sensor exhibits excellent glucose sensing performance within a concentration range of 0.2 mM to 14 mM, with a detection limit of 0.25 mM and a rapid response time of 5–10 s. The LS-TES is cost-effective, highly stable, and reusable, maintaining consistent electrical responses across ten cycles of alternating droplet measurements. This work presents a preclinical assessment approach, specifically for urine glucose monitoring, utilizing an innovative sensor based on the liquid–solid interface. The proposed concept has the potential to serve as an individual indicator for early medical symptom detection, offering relief to a large number of patients.

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