Vittayakorn, Naratip

Preferred name

Alternative Name

Vittayakorn, N.

Vittayakorn, Narathip

Main Affiliation

School of Science

naratip.vi@kmitl.ac.th

Now showing 1 - 10 of 28

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Tailoring charge affinity, dielectric property, and band gap of bacterial cellulose paper by multifunctional Ti2NbO7 nanosheets for improving triboelectric nanogenerator performance
(2023-02-01)
Sriphan, Saichon
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Pharino, Utchawadee
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Charoonsuk, Thitirat
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Pulphol, Phieraya
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Pakawanit, Phakkhananan
Transparent, flexible, and high-performance triboelectric nanogenerator (TENG) from nature-derived materials are required for sustainable society development. However, low triboelectricity from natural material is generally observed. Tunable electronic band diagram (EBD) through facile manipulation is one of the efficient methods to promote the TENG output, requiring fundamental, in depth understanding. Herein, we employed the high quality, single crystal-like Ti<inf>2</inf>NbO<inf>7</inf> nanosheets (NSs) with dual dielectric and semiconducting properties as filler for bacterial cellulose (BC)-based TENG. Several techniques including X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), ultraviolet—visible (UV—vis) absorption, energy dispersive X-ray spectroscopy (EDS), and synchrotron radiation X-ray tomographic microscopy (SRXTM) were applied to characterize the long-range structure, microstructure, optical properties, elemental composition, and three-dimensional (3D) distribution of components in the composites. The semi-transparent and flexible 5 vol.% Ti<inf>2</inf>NbO<inf>7</inf> NSs/BC preserved the integrity of cellulose, contained well-dispersed nanosheets, reduced optical band gap (4.20 vs. 5.75 eV for BC), and increased surface roughness. The dielectric permittivity and conductivity increased with nanosheets content. Adding negatively-charged Ti<inf>2</inf>NbO<inf>7</inf> NSs could regulate the charge affinity of BC composite via shifting of Fermi energy over that of Al. It is found that adding 5 vol.% NSs into the BC film improved electrical outputs (~ 36 V and ~ 8.8 µA), which are 2–4 times higher than that of pure BC, even when paired with Al which lies adjacent in triboelectric series. Our work demonstrated the method to enhance BC-based TENG performance through EBD regulation using multifunctional Ti<inf>2</inf>NbO<inf>7</inf> NSs. [Figure not available: see fulltext.]
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Highly Flexible Tribovoltaic Nanogenerator Based-on P-N Junction Interface: Comparative Study on Output Dependency Dominated by Photovoltaic Effect in Freestanding-Mode
(2023-10-18)
Sriphan, Saichon
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Worathat, Supakarn
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Pharino, Utchawadee
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Chanlek, Narong
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Pakawanit, Phakkhananan
The emergence of tribovoltaic nanogenerators (TVNGs) paves the way for developing a new kind of semiconductor-based energy harvester that overcomes the restriction of low output current in a conventional approach. The traditional TVNG generally depends on the frictional pair between two rigid semiconductors (or metal-semiconductor), limiting the practicability of flexible and portable electronics. Recent developments require the fundamental understanding of charge generation in diverse operating modes and structures. Here, a flexible TVNG based on the p-Cu<inf>2</inf>O/n-g-C<inf>3</inf>N<inf>4</inf> interface is presented. Operating in a freestanding mode, the proposed TVNG can generate a stable signal in any optical conditions including UV illumination, dark, and ambient. Under UV illumination, the electrical outputs of the TVNG reach 0.43 V and 2.1 µA cm−2, which are significantly larger than those obtained from dark and ambient conditions. The results demonstrate the coupling effect of three phenomena: tribovoltaic, photovoltaic, and triboelectric effects, and the unique mechanism to the observed signal is proposed. Additionally, the TVNG shows the practical feasibility of energy harvesting with capacitor charging and charge-boosting circuits. This study showcases the unique concept with potential for developing a novel flexible nanogenerator in many aspects, including material, structure, and fundamental mechanism.
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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
;
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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AC Conductivity and dielectric properties of lepidocrocite-type alkali titanate tunable by interlayer cation and intralayer metal
(2020-11-02)
Charoonsuk, Thitirat
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Sriphan, Saichon
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Pulphol, Phieraya
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Vittayakorn, Wanwilai
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Vittayakorn, Naratip
The lepidocrocite-type layered alkali titanate AxMyTi2-yO4 has diverse chemical compositions with variation in charge per formula unit x, the interlayer cation A+, and the intralayer metal M. Despite this multivariable nature, the composition dependence of physical properties is not well explored. We report herein the AC conductivity and the complementary dielectric properties of Cs0.7M0.35Ti1.65O4, K0.8M0.4Ti1.6O4 (M = Zn, Ni), and the mixed-interlayer ion Cs0.6K0.1Zn0.35Ti1.65O4. For Cs0.7Zn0.35Ti1.65O4, the total AC conductivity is ~7 × 10-8 to 2 × 10-6 S·cm-1 at 200-350 °C, associating with an activation energy Ea ∼865 meV. Meanwhile, the conductivity of K0.8Zn0.4Ti1.6O4 is higher by 1 order of magnitude at much lower temperature (25-150 °C) and a smaller Ea ∼250 meV. This difference originates from the compositional robustness of the cesium-containing samples, contrasting with the sintering-induced changes in the potassium analogues. For the latter, the loss of the interlayer K+ ion results in (i) generation of carriers due to charge compensation, (ii) reduction of sheet charge density and weakening of electrostatic attraction, and (iii) widening of the interlayer distance, all contributing to a lower Ea in K0.8M0.4Ti1.6O4. The angular frequency dependence of conductivity, dielectric permittivity (up to a colossal value of 109), and dielectric loss follows the universal power law. Our work demonstrates the potential of simple compositional variation for electrical properties tuning, prompting a more in-depth investigation covering a wider range of possible candidates of x, A+, and M in lepidocrocite titanate.
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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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Effect of Adsorbed Water and Temperature on the Universal Power Law Behavior of Lepidocrocite-Type Alkali Titanate Ceramics
(2021-06-17)
Sriphan, Saichon
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Pulphol, Phieraya
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Charoonsuk, Thitirat
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Maluangnont, Tosapol
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Vittayakorn, Naratip
The ubiquitous (re)adsorption of atmospheric water by functional ceramics leads to some applications such as humidity sensing; at the same time, this phenomenon complicates the understanding of the nature of original conducting species. We presented herein the effects of adsorbed water on the electrical properties and charge transport of K0.8Zn0.4Ti1.6O4, Cs0.7Zn0.35Ti1.65O4, and Cs0.6K0.1Zn0.35Ti1.65O4 lepidocrocite-type alkali titanate ceramics. A small amount of atmospheric water (0.02-0.33 mol/mol) is merely adsorbed on the external surface but not intercalated into the interlayer space. In temperature scan experiments, water sorption leads to the dielectric permittivity/loss hysteresis loops, where the values upon cooling are unusually larger than those upon heating. In frequency scan experiments, multiple frequency- and temperature-dependent anomalies are detected. The AC conductivity was fitted to the Jonscher universal power law response (σ′AC = σDC + Aωs) from 101 to 106 Hz and 400-25 °C. We observed an uncommon U-shaped A(T) but an inverted U-shaped s(T), regardless of the interlayer ion, charge per formula unit, or pellet density. These plots allow a qualitative description of (i) the apparent activation energy, (ii) the effective dimension of the conduction pathway, and (iii) the charge carrier concentration, all as a function of the temperature under the influence of atmospheric water. Our physical interpretation is potentially applicable to other systems, providing insights into the (unintentional) water-induced conductions and complementing rigorous but time-consuming investigations by controlled humidity experiments.
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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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Hybrid piezoelectric-triboelectric nanogenerators for flexible electronics: Recent advances and perspectives
(2022-09-01)
Sriphan, Saichon
;
Vittayakorn, Naratip
For several decades, a focus has been placed on the development of future flexible electronics, including electronic skin, wearable devices, environmental monitoring systems and the Internet of things (IoT) network. The triboelectric nanogenerator (TENG) attracted attention by developing this technology due to its high-performance, facile design/fabrication, light-weight and high flexibility. However, in some cases, the use of pristine triboelectric material for a TENG operation might be insufficient for efficiently driving/sensing small-to-medium electronic systems without modification. Hence, a hybrid strategy between piezoelectric and triboelectric effects from piezoelectric nanogenerator (PENG) and TENG is proposed. This unique characteristic serves as a combination of polarized charges from the piezoelectricity and surface charges from the triboelectric effect when the hybrid device is subjected to mechanical stress. This provides a higher yield of charge density, which relates to a higher magnitude of output current. Through outstanding performance, the hybrid PENG and TENG can be applied in various fields, especially in flexible electronics technology. Herein, an overview of recent advances for hybrid PENG and TENG development is presented, including basic mechanisms, related theories, coupling effect, performance factors, and potential applications. The final part also discusses the challenges and perspectives for further development and the opportunity for the commercialization of this nanogenerator.
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Simple Fabrication of Porous 3D Substrate Polydimethylsiloxane (PDMS) Composited with Polyvinylidene Fluoride-co-Hexafluoropropylene (PVDF-HFP) for Triboelectric Nanogenerator
(2022-01-01)
Pakawanit, Phakkhananan
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Pharino, Utchawadee
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Charoonsuk, Thitirat
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Sriphan, Saichon
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Pongampai, Satana
Owing to their structural advantages over bulk polymers, porous 3D substrates possess immense potential in triboelectric energy generation. This work reports the effective effort to fabricate the porous structure of polydimethylsiloxane, also known as the sponge-PDMS, by a simple template method. The sodium chloride salt from commodity product is used to create the 300 μm size of pores within the PDMS elastomeric layers, turning affects to the mechanical deformability of the triboelectric nanogenerator (TENG). The inner face of those pores is composited with the PVDF-HFP particles as a piezoelectric fillers. The presence of those fillers can be confirmed and their distribution within porous PDMS is 3D visualized by the synchrotron radiation X-ray tomography. The spatial distribution of the PVDF-HFP made it possible to fabricate the piezo-embedded macroporous TENG with high output power of 7.84 μW, giving over 2-fold enhancement, compared with the sponge-PDMS and even more when compared with the flat PDMS film under the same mechanical force.
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Equivalent circuit model and simulation for dynamic sliding droplet-based triboelectric nanogenerators
(2024-11-01)
Sriphan, Saichon
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Pharino, Utchawadee
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Chaithaweep, Kanokwan
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Vittayakorn, Naratip
Recently, there has been an increase of attention to employing liquid-solid contact to harvest or sense energy from water flow. Water's considerable deformability, however, makes it challenging to investigate how water moves dynamically in relation to a water-based triboelectric nanogenerator's (TENG) output characteristic. There are a few studies examining the fundamental mechanism of a droplet-based energy generator (DEG). In addition, such an electrical model has been established based on the consideration of instantaneous output at a specific period in a saturated state. Here, we first propose the circuit model and governing equations for simulating the double-electrode DEG's electrical output, comprehensively covering the L-S contact's dynamic process. Four essential stages of charge generation of the DEG are considered in unsaturated and saturated stages. The proposed model is verified systematically with the experimental data. The relationship between structural parameters and output performance of the DEG, such as internal capacitance, residual charge, dielectric constant, droplet spreading size, and dielectric thickness, has emerged. In summary, our model effectively establishes theoretical guidance, which paves the way for high-performance supply and sensor applications based on the L-S interface.

Vittayakorn, Naratip

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