Self-powered wireless temperature sensor with piezoelectric energy harvester fabricated with metal-MEMS process

This paper presents a self-powered wireless temperature sensor powered with a micro piezoelectric energy harvester. The piezoelectric energy harvester is a cantilever beam design fabricated with metal-MEMS process on stainless steel substrates. The energy harvester is tuned to have resonant frequency around 120Hz and the bimorph version can generate more than 400μW power output when driven with vibration levels of 1.5g acceleration at resonance. A shaker simulated the vibrations of motors general seen in air conditioning system with a vibration level around 0.5g is used to drive the piezoelectric energy harvesters and has a power output around 50μW power. An interfacing circuit with energy buffer is used to accumulate electrical energy in a capacitor and then turn on the Bluetooth wireless module to send temperature readings measured from internal temperature sensor to a smartphone intermittently. The Bluetooth module can be turn on for around 1 second to send the readings to a smartphone for every 1.5 minutes.