Versatile Fabrication Methods for Wearable Thermo-electrochemical Cells

Emerging markets for wearable electronics have stimulated a rapidly growing demand for the commercialisation of flexible and reliable energy storage and conversion units, which includes batteries, supercapacitors, and thermo-electrochemical cells (thermocell). Among them, thermocell have attracted significant research attention in recent years owing to their ability to continuously convert body heat into electrical energy. The commercial viability of wearable thermocells has long been limited by their low power output and complex fabrication methods. Great progress has been made in developing flexible electrode materials, gel electrolytes and encapsulation materials. However, it is still a main challenge to develop flexible electrodes on a various-scale and in a cost-effective manner. At present, carbon electrodes are commonly fabricated using a vacuum filtration method. However, fine carbon nanoparticles can be drawn through the filter paper pores via suction force, resulting in blockage of the filtrate and wastage of the ink materials. Meanwhile, this fabrication method is time consuming and reduces the overall fabrication efficiency of devices. Therefore, additional fabrication methods exert pressure on developing simple and scalable techniques, such as laser-etching, 3D printing, and drop coating. The main goal for this study is to fabricate high performance electrodes for wearable thermocell devices in simple and scalable ways. A wearable poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonate) (PEDOT/PSS or PEDOT: PSS) based film was firstly prepared via a laser-etching method and assembled to be wearable all-solid-state thermocell. For applications of this wearable thermocell, a flexible watch-strap shaped thermocell that could harvest body heat, charge supercapacitors, and light a green LED. This systematic investigation and optimization of 3D structured laser-etched electrode, gel electrolyte, and device architectures introduced has great significance for the realization of body heat harvesting and application in real self-powered wearable electronics.