Collect energy from skin temperature for battery-free and portable electronics

Illustration of the concept of soft electrodes with soft electrodes and soft heat conductors (s-HCs) for applications to self-powered circuits. The left insert is a photograph of thermoelectric legs (TE) based on bismuth telluride (Bi2Te3) and the right insert is an optical image of a TEG incision that meets the insert. Scale bars, 5 to 1 mm. Credit: Korea Institute of Science and Technology (KIST)

Development of flexible thermoelectric devices with maximum flexibility and high efficiency; enabling the mass production of self-powered portable devices through automated mass production through an automated process.

A thermoelectric device is a device for converting energy using a voltage generated by the temperature difference between two ends of a material; is able to convert heat energy, such as hot waste from industrial sites, into electricity that can be used in everyday life. Existing thermoelectric devices are rigid, consisting of hard, metal-based electrodes and semiconductors that interfere with the complete absorption of heat sources from an irregular surface. Therefore, recent research has been actively conducted that is capable of developing flexible thermoelectric devices, thermoelectric devices that are able to create a close relationship with different heat sources, such as human skins and hot water pipes.

Korean Institute of Science and Technology (BOX) announced that a collaborative team led by Dr. Seungjun Chung of the Soft Hybrid Materials Research Center and Professor Yongtaek Hong of the Seoul National University’s Department of Electrical and Computer Engineering (SNU, OH President Se-Jung) have developed flexible thermoelectric devices. high energy generation performance, maximizing flexibility and heat transfer efficiency. The research team also presented a mass production plan through an automated process that includes the printing process.

Hot surface warning gloves

Schematic illustration of hot surface warning gloves with self-powered LED system and light masking packages. Photographs showing a display of TEG-attached gloves when used to capture various hot objects, such as a bottle and a pot. The inserts show an enlarged view of the self-powered system and packages. The conformal contact between the TEG-attached gloves and the 3D surfaces of heat sources creates a bright “H” symbol without the aid of an external energy source. Scale bars, 5, 5 cm and 5 mm. Credit: Korea Institute of Science and Technology (KIST)

Regarding the substrates used for research on flexible thermoelectric devices, their efficiency of heat energy transfer is low due to their very low thermal conductivity. The efficiency of heat absorption is also low due to the lack of flexibility, forming a heat-protective layer, such as air, when it comes in contact with a heat source. To address this problem, thermoelectric devices based on highly flexible organic materials are being developed, but their application to laptops is not easy because they have significantly lower performance compared to rigid thermoelectric devices based on inorganic materials.

Seungjun Chung

Dr. Seungjun Chung, Center for Research on Soft Hybrid Materials, KIST. Credit: Korea Institute of Science and Technology (KIST)

The aforementioned research team improved the flexibility by lowering the resistance of the thermoelectric device by connecting a high-performance thermoelectric device based on inorganic material to a stretchable substrate composed of silver nanowires. The thermoelectric device developed showed excellent flexibility, thus allowing stable operation even when folded or stretched. In addition, metal particles with high thermal conductivity were incorporated into the expandable substrate, increasing the heat transfer capacity by 800% (1.4 W / mK) and generating energy in a factor higher than three. (The temperature difference between the two ends of the thermoelectric device developed was 40? Or more. 7 mW / cm2 of electricity was generated. Only 7 μW / cm2 of electricity was generated from human skin from body temperature.) At the same time, the researchers automated the entire complex process. from the soft process to the development of the thermoelectric device, thus enabling mass production of the device.

The developed device can be used as a high temperature sensor in industrial areas or as a sensor to detect distance without a battery by autonomously driving inside and outside a car using the temperature difference. Therefore, it is hoped that the device will be able to solve the problem of the power source of a battery-based sensor system, which is at risk of explosion in high temperature environments.

Dr. Seungjun Chung, with KIST, said: “This research has shown the use of clothing such as high temperature sensor gloves using external heat sources. In the future, we will develop a flexible thermoelectric platform to operate clothing with only body temperature.” The findings are significant because the functional composite materials developed in this research, thermoelectric device platforms, and high-performance automated processes may help to market battery-free garments in the future. ”

Reference: Byeongmoon Lee, Hyeon Cho, Kyung Tae Park, Jin-Sang Kim, Min Park, Heesuk Kim, Yongtaek Hong and Seungjun “High performance compatible thermoelectric generators with soft self-assembled magnetic heat conductors for self-powered portable electronics” . Chung, November 23, 2020, Nature Communications.
DOI: 10.1038 / s41467-020-19756-z

This research was supported by the Ministry of Science and ICT (MSIT) and was carried out as part of the KIST Institutional R&D Program, the Korean National Research Foundation’s Creative Materials Discovery Program, the Creative Convergence Research Project, and the Global. Border project. The results of the study were published in the latest issue of the international journal Nature Communications (IF: 12.121).

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