Hyunok Cho

A wrist-band coupled, human skin based triboelectric generator for harvesting biomechanical energy

Effectively harvesting ambient mechanical energy is very important for realizing self-powered and autonomous electronics, which has numerous applications in sensor networks, wireless devices, and wearable or implantable electronics, etc. This paper presented a human skin based triboelectric generator (TEG), coupled to a light and flexible wrist-band to be used for wearable smart device applications. We developed a simple, cost effective, and feasible fabrication method of a micro-structured Polydimethylsiloxane (PDMS) thin film as one of the triboelectric layers, the other layer being the human skin. Here, electricity was generated by repetitive contact-separation actions between these two triboelectric surfaces. Results showed the fabricated prototype is capable of generating a maximum open circuit voltage of 28.2V and 12μW peak power by mild finger pressing over the device at 2.9Hz frequency. The proposed harvester responds to low-frequency kinetic energy of human-body-induced motion; so it has the potential to convert the mechanical energy of finger pressing into electrical energy.

Development of Multi-Degree-Of-Freedom Piezoelectric Energy Harvester Using Interdigital Shaped Cantilevers.

A piezoelectric vibration energy harvester with interdigital shaped cantilever was developed by using silicon bulk micromachining technology. The proposed energy harvester was designed to obtain multi degree-of-freedom (m-DOF). Most of the piezoelectric vibration energy harvesters are comprised of mass-loaded cantilever beams having several resonant frequencies. The second resonant frequency of such a device has lower amplitude compared to its first resonant frequency (fundamental frequency). Therefore, the interdigital shaped cantilever has been proposed for multiple fundamental resonant frequencies. The fabricated piezoelectric vibration energy harvester is composed of main cantilever (MC), sub-main cantilever (SMC), and secondary cantilevers (SC). MC surrounds SMC and SC which have same dimension of 5600 x 800 x 10 μm3. The fabricated piezoelectric energy harvester can generate 51.4 mV(p-p) and 11 mV(p-p) of output voltages at 24.2 Hz and 33 Hz of its resonant frequencies by MC. Moreover, it can generate 8 mV(p-p) and 6.6 mV(p-p) of output voltages at 24.2 Hz and 33.2 Hz of its resonant frequencies by SMC; and 364 mV(p-p) of output voltage at 33.6 Hz of its resonant frequency by SC.