Klongratog, Bhanupol

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Klongratog, Bhanupol
Alternative Name
Klongratog, B.
Klongratog, Bhanupo
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Email
bhanupol.kl@kmitl.ac.th

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    High-performance flexible thermoelectric generator based on silicone rubber and cover with graphite sheet
    (2024-01-05)
    Gobpant, Jakrit
    ;
    Klongratog, Bhanupol
    ;
    Rudradawong, Chalermpol
    ;
    Sakdanuphab, Rachsak
    ;
    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 cm<sup>2</sup> FTEG device was fabricated and covered with a bendable substrate. Silicon rubber (0.08 Wm<sup>−1</sup>K<sup>−1</sup>), silicon rubber added 5% graphene (0.14 Wm<sup>−1</sup>K<sup>−1</sup>), and graphite sheets (15 Wm<sup>−1</sup>K<sup>−1</sup>) 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/cm<sup>2</sup> 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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    Flexible thermoelectric generator with radiative cooling for body-heat-driven self-powered Bluetooth low energy sensing system
    (2025-10-01)
    Gobpant, Jakrit
    ;
    Van Toan, Nguyen
    ;
    Ono, Takahito
    ;
    Tuoi, Truong Thi Kim
    ;
    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/cm<sup>2</sup> 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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    Synthesis of Fe–Cu Alloys via Ball Milling for Electrode Fabrication Used in Electrochemical Nitrate Removal from Wastewater
    (2025-07-01)
    Hayeedah, Hannanatullgharah
    ;
    Sakulkalavek, Aparporn
    ;
    Klongratog, Bhanupol
    ;
    Somdock, Nuttakrit
    ;
    Srirach, Pisan
    Fe and Cu powders were mixed at a 50:50 ratio. Then, Fe-Cu alloys were prepared using the ball milling technique with different milling times of 6, 12, 18, 24, 30, 36, and 42 h. The crystalline structure was analyzed using X-ray diffraction (XRD), and it was found that the optimum milling time was 30 h. The homogeneity of the Fe and Cu elements in the Fe–Cu alloys was analyzed using the scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM–EDX) mapping technique. Additionally, the crystal orientation of the Fe–Cu alloys was investigated using transmission electron microscopy (TEM). To fabricate the cathode for nitrate removal via electrolysis, an Fe–Cu alloy milled for 30 h was deposited onto a copper substrate using mechanical milling, then annealed at 800 °C. A pulsed DC electrolysis method was developed to test the nitrate removal efficiency of the Fe–Cu-coated cathode. The anode used was an Al sheet. The synthesized wastewater was prepared from KNO<inf>3</inf>. Nitrate removal experiments from the synthesized wastewater were performed for durations of 0–4 h. The results show that the nitrate removal efficiency at 4 h was 96.90% compared to 74.40% with the Cu cathode.
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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
    ;
    Klongratog, Bhanupol
    ;
    Rudradawong, Chalermpol
    ;
    Sakdanuphab, Rachsak
    ;
    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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