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Enhancement of thermoelectric performance and mechanical reliability in electrodeposited chitosan nanofiber-bismuth telluride nanocomposite
(2026-07-01)
Tian, Jianghan
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Gobpant, Jakrit
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Van Toan, Nguyen
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Theekhasuk, Nattharika
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Pham, Cong Kha
Thermoelectric generators (TEGs) offer a promising route for converting waste heat into electrical energy; however, the practical implementation of high-performance micro-TEGs (μTEGs) is limited by the material performance and mechanical fragility of thick bismuth telluride (Bi<inf>2</inf>Te<inf>3</inf>) films. Although thick thermoelectric layers are required to sustain sufficient temperature gradients, conventional fabrication often induces residual stress, leading to cracking and structural failure. In this work, we introduce a sustainable synthesis strategy by incorporating bio-derived chitosan nanofibers (ChNFs) into the electrodeposition process. The amino and hydroxyl functional groups of ChNFs promote interfacial bonding and nucleation, enabling the rapid growth of dense, crack-free composite films with thicknesses up to 1000 μm. The introduction of ChNFs also creates abundant phonon-scattering interfaces, significantly reducing lattice thermal conductivity from 1.48 to 0.29 W m−1 K−1 and resulting in a 303% increase in the room-temperature figure of merit (ZT), from 0.12 to 0.50. At an optimal loading of 0.0123 wt%, the composite films exhibit a 15% increase in hardness while maintaining structural integrity. These results demonstrate a multifunctional materials design strategy that simultaneously enhances thermoelectric performance, mechanical robustness, and fabrication scalability. The ChNF–Bi<inf>2</inf>Te<inf>3</inf> nanocomposites provide a viable green pathway for developing reliable thick films for next-generation self-powered electronics and compact waste-heat harvesting systems.
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Chemical etching of glass substrates
(2026-01-01)
Van Toan, Nguyen
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Toda, Masaya
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Xue, Gaopeng
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Gobpant, Jakrit
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Sakulkalavek, Aparporn
MEMS and microfluidics represent the forefront of technological innovation, spearheading a transformative era in precision control over fluids and mechanical components at scales that were once unimaginable. These groundbreaking technologies have transcended conventional boundaries and are now at the heart of numerous applications [1-3], spanning a wide spectrum of industries. From pioneering advancements in advanced medical diagnostics, where the manipulation of minute biological samples is essential, to the intricate networks that facilitate seamless telecommunications [4, 5], MEMS and microfluidics have become indispensable tools, exemplifying unparalleled efficiency, versatility, and cost-effectiveness. The ability to navigate and manipulate the microscopic and nanoscopic realms with precision opens new frontiers, promising advancements that not only redefine our technological landscape but also significantly impact the way we approach challenges across diverse sectors.
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Flexible thermoelectric cooler with optimized fill factor and radiative cooling integration for energy-efficient wearable thermal management
(2025-12-01)
Gobpant, Jakrit
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Sakulkalavek, Aparporn
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Sriniratkul, Pannarai
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Sa-I, Saowanee
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Rudradawong, Chalermpol
The growing demand for skin-interfaced electronics in health monitoring, sports, and personal comfort highlights the need for compact, energy-efficient, and conformable cooling systems. However, existing thermoelectric coolers (TECs) are rigid, bulky, and power-intensive, making them unsuitable for wearable applications. To address this limitation, we present a flexible thermoelectric cooler (FTEC) with a compact footprint of 40 × 40 × 2.26 mm3, featuring discrete p- and n-types thermoelectric leg arrays with systematically varied fill factors (FF = 9 %, 16 %, 25 %, and 36 %). Optimization revealed that the 16 % FF configuration provides the most energy-efficient architecture, achieving a cold-side temperature of −5.9 °C and a coefficient of performance (COP) of 3.25 at 6 W input, while balancing cooling capacity and electrical loss. To improve heat dissipation without increasing bulk, ultrathin graphite and radiative cooling (RC) layers were integrated. Three configurations, including baseline (no thermal layer), graphite-enhanced, and RC-enhanced FTECs, were systematically evaluated. Under ambient conditions (33 °C), the RC- enhanced FTEC maintained a cold-side temperature of approximately 23 °C for 6 h during low-current operation of 0.3 A. Beyond intrinsic performance, the optimized FTEC was benchmarked against both commercial rigid TEC modules and state-of-the-art flexible TECs. Compared to widely used Peltier devices (TEC1–12705 and TEC1–12710), our FTEC achieved comparable ΔT with nearly 65 % lower power consumption, owing to fill factor optimization and RC-enhanced heat rejection. Mechanical flexibility was validated through bending tests, confirming both thermal and electrical stability. Finally, integration with an ESP32-based proportional–integral–derivative (PID) control system enabled real-time wearable cooling, successfully reducing skin temperature from 33 °C to 31 °C in on-body trials. This work demonstrates.
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Flexible thermoelectric generator with radiative cooling for body-heat-driven self-powered Bluetooth low energy sensing system
(2025-10-01)
Gobpant, Jakrit
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Van Toan, Nguyen
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Ono, Takahito
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Tuoi, Truong Thi Kim
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Tran, Ngoc Dang Khoa
Wearable electronics and wireless IoT sensors are increasingly expected to operate in a self-powered manner. However, their practical deployment remains limited due to the lack of compact, flexible, and sustainable energy sources. Thermoelectric generators (TEGs), which convert body heat into electricity, present a promising solution but are typically hindered by small temperature gradients and the requirement of bulky heat sinks that compromise flexibility. To address these challenges, we developed an ultra-thin flexible thermoelectric generator (FTEG) integrated with a radiative cooling (RC) layer that passively enhances heat dissipation under natural convection. The device, fabricated using high-performance thermoelectric materials on a soft silicone substrate, maintained a total thickness of just 2.26 mm. Finite element modeling and experimental validation confirmed that the RC layer effectively increased the temperature gradient across thermoelectric legs, significantly improving the output power compared to conventional graphite-based or no-cooling designs. The FTEG achieved a maximum normalized power density of 3.51 μW/cm2 under temperature conditions representative of wearable use (T<inf>skin</inf> of 32 °C and T<inf>ambient</inf> of 26 °C). The harvested energy was then stored using a power management circuit and capacitor. This stored energy was successfully used to power a Bluetooth Low Energy (BLE) sensing module, enabling stable wireless transmission driven entirely by body heat. These results highlight the practical potential of integrating passive radiative cooling into flexible thermoelectric systems, paving the way for high-performance, battery-free wearable electronics and autonomous IoT applications.
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Optimizing fabrication processes for scalable production of flexible thermoelectric modules: A case study on self-powered IoT systems
(2025-09-01)
Gobpant, Jakrit
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Klongratog, Bhanupol
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Rudradawong, Chalermpol
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Sakdanuphab, Rachsak
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Limsuwan, Pichet
This study explores the optimization of fabrication processes for flexible thermoelectric generators (FTEGs) to enhance their performance and scalability for industrial applications, with a focus on integrating them into self-powered Internet of Things (IoT) systems. The research investigates the impact of silicone layer thickness and applied fabrication pressures on the mechanical stability, energy harvesting efficiency, and power output of FTEGs. Results demonstrate that reducing the thermal conductivity of the silicone filler and optimizing the fabrication pressure significantly improves the performance of FTE modules. The optimized FTEGs, featuring a series-parallel configuration, achieve a power density of 5.2 mW/cm² under a temperature difference of 50 °C, surpassing prior benchmarks. The developed system efficiently harvests waste heat, charges a battery, and powers an IoT module for real-time monitoring of temperature, humidity, and carbon monoxide levels. These findings highlight the potential of FTEGs as a sustainable solution for energy harvesting and self-powered industrial monitoring applications.
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High-performance flexible thermoelectric generator based on silicone rubber and cover with graphite sheet
(2024-01-05)
Gobpant, Jakrit
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Klongratog, Bhanupol
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Rudradawong, Chalermpol
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Sakdanuphab, Rachsak
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Junlabhut, Prasopporn
Harvesting thermal energy through a flexible thermoelectric generator (FTEG) offers an excellent micro-power solution for energizing node sensors in the realm of Internet of Things (IoT) and wearable electronics. Nonetheless, current FTEG suffer from drawbacks including low efficiency, significant thermal resistance, and complex manufacturing procedures. In this study, a high-performance FTEG using silicone rubber was designed and fabricated using a straightforward process. The finite-element method was used to optimize the copper electrode thickness, and the bendable substrate layers with various thermal conductivity were studied for the first time. The copper electrode thickness of 0.1 mm was selected because it offers high flexibility and bendability while still providing a relatively high-power output. The 5 × 5 cm2 FTEG device was fabricated and covered with a bendable substrate. Silicon rubber (0.08 Wm−1K−1), silicon rubber added 5% graphene (0.14 Wm−1K−1), and graphite sheets (15 Wm−1K−1) were used as bendable substrates. The FTEG cover with graphite sheets has a maximum output voltage of 1.1 V under a temperature difference (ΔT) at 65 °C. Its maximum output power is 162.4 mW, corresponding to a power density of 6499.1 µW/cm2 under the same above ΔT. The experimental findings indicated that integrating a bendable substrate with high thermal conductivity and electrical insulation properties enhances the performance of the FTEG.
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Enhancement of thermoelectric properties in rapidly synthesised β-Cu2Se using optimized Cu content and microwave hybrid heating
(2024-01-15)
Sakulkalavek, Aparporn
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Rudradawong, Chalermpol
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Gobpant, Jakrit
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Harnwunggmoung, Adul
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Limsuwan, Pichet
To our knowledge, this is the first study to successfully synthesise high-temperature-phase copper selenide (β-Cu<inf>2</inf>Se) at room temperature using rapid microwave hybrid heating (MHH). Controlling the starting Cu/Se ratio is the critical parameter for adjusting the content of α- and β-phases in the as-synthesised sample. The relatively low Cu composition causes impurities to form in the Cu<inf>3</inf>Se<inf>2</inf> phase, deteriorating the thermoelectric (TE) properties of the Cu<inf>2</inf>Se material. The β phase formation at room temperature promotes electrical conductivity. The thermal conductivities of the Cu<inf>2.0</inf>Se samples were 0.5–0.8 Wm−1K−1 at 303–673 K. A strong electronic-phonon interaction may potentially couple electronic thermal conductivity (κ<inf>e</inf>) and lattice thermal conductivity (κ<inf>L</inf>), resulting in incomplete separability of κ<inf>L</inf> and κ<inf>e</inf> in the β-Cu<inf>2.0</inf>Se sample. The Cu<inf>2.0</inf>Se exhibited a ZT value of 0.65 at 523 K because of its considerably lowered thermal conductivity.
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Graphene addition improved figure of merit in SnTe prepared by the rapid hybrid microwave solid-state method
(2022-02-01)
Gobpant, Jakrit
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Somdock, Nuttakrit
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Limsuwan, Pichet
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Sakulkalavek, Aparporn
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Sakdanuphab, Rachsak
We successfully synthesised SnTe-based powders (SnTe, Sn<inf>0.95</inf>Bi<inf>0.05</inf>Te, and SnTe with graphene addition) by a hybrid microwave solid-state method. This demonstrated comparable thermoelectric performance to the conventional heating method but had low energy consumption and rapid synthesis. Graphene addition to SnTe materials resulted in significant reduction of thermal conductivity. The SnTe with 5 wt% graphene exhibited a reduction in overall thermal conductivity from ∼10 W m−1 K−1 for SnTe to ∼2 W m−1 K−1 at 325 K and showed a moderate power factor. The Debye model was used to explain the origin of the effects of graphene on lattice thermal conductivity. The dimensionless figure of merit was increased by five times, from 0.07 for SnTe to 0.35 for SnTe with 5 wt% graphene. Our results demonstrated an effective method and additive material to synthesise and enhance the thermoelectric properties of SnTe materials.

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