Energy Harvesting by Vibrations With MEMS Piezoelectric Benders

Piezoelectric micro benders are fabricated and tested to demonstrate energy generating performance. Trapezoidal and diagonal unimorph PZT benders with an interdigitated electrode pattern are utilized. The d₃₃ mode design is beneficial for the micro energy harvesting devices because it can generate higher voltage than that of the d₃₁ mode design. It can also eliminate a bottom electrode by only using an interdigitated top electrode which facilitates fabrication, as opposed to the d₃₁ mode design that requires both top and bottom electrodes. The MEMS benders consist of layers of SiO₂/SiN_x/ZrO₂/PZT, and a top Au/Cr interdigitated electrode. The experimental results indicate that the fundamental frequencies of the micro benders are about 9.1 kHz for the trapezoidal bender and 18.48 kHz for the diagonal bender, respectively. The micro trapezoidal bender can generate power of approximately 1.4μW into a 680 kΩ resistive load at the resonant frequency. The diagonal bender can generate power of about 18.2 μW into a 100 kΩ resistive load at the resonant frequency.