Wearable electronics based on polyamide fibrous membrane powered by hydrogenerator

Abstract

Accompanied by radical development of microelectronic integration and miniaturization in electronic industry, wearable electronics are vividly blossoming for widespread applications such as energy harvesting, health monitoring, man-machine interaction. Flexible circuits functions as the circuit connection and becomes an indispensable component for electronics. Efforts have been devoted to improving the reliability of circuits, operating life as well as sustainable power supply. While it remains a huge challenge to fabricate wearable electronics with integrating ability into fabrics, qualified working durability and sustainable self-power function for practical applications. To address the issues, this thesis carries out a systematic investigation on wearable circuits with enhanced durability, washability, scalability, and self-power module towards practical applications. Firstly, a stable and washable interconnector has been fabricated, with fibrous polyamide membrane as substrate, plating Cu/Ni multilayer as conductive layer, and parylene as robust encapsulation. Fibrous polyamide membrane was elaborately chosen because of their high thermal and dimensional stability, excellent dielectric properties, weather resistance and wet strength. Metal plating was employed to guarantee excellent conductivity (14 mΩ/sq). Besides, the interconnector exhibits superior electromechanical stability after abrasion of 50000 cycles, bending of 10000 cycles, and machine washing of 50 times. The work presents a facile and effective method to fabricate highly flexible and durable interconnector. Since metal plating and parylene encapsulation are well explored, the second target is to develop fibrous circuit board assemblies (FCBA) based on polyamide fibrous membrane for broad applications. As-made circuits are micron-scale accuracy, highly conductive, endurable, and washable. Furthermore, the FCBA exhibits an enhanced water resistance for over 20 days and a competent load endurance of 10 N under tension. More importantly, FCBA can achieve seamless integration with fabrics and demonstrates desirable lifespan in harsh environments. Lastly, it is highly desirable to own a green, scalable, sustainable power sources for wearable electronics. Here a green and sustainable moisture-enabled generator was developed based on the rational ingredients of PVA/PA with glycerol (HMEG). Thanks to synergistic effect of moisture-absorbing/maintaining as well as enhanced ionic concentration, one single HMEG unit can generate a continuous voltage of ~0.8 V, a current density of 238 μA cm-2, an optimal power density of 5.9 mW cm-3. A linearly scaleup voltage (210 V) and current (7 mA) are easily achieved to power many electronics. In-situ FTIR and Raman reveals that the moisture-induced directional movement of protons within the HMEG accelerates electric power generation. In summary, the wearable electronics based on fibrous polyamide membrane have been successfully developed. On one hand, parylene encapsulation was employed to protect the interconnector and circuit board, which enhances electromechanical durability, washability. The wearable electronics achieve seamless integration with fabrics. On the other hand, a self-powered module was achieved by preparing moisture-enabled generator for driving wearable electronics. Overall, this systematic study develops wearable electronics within fabrics and qualified lifespan for practical applications. More importantly, wearable electronics address the challenge of green, sustainable self-powering problem. This positive investigation offers a guide to develop more wearable self-powered electronics in the future.