This prototype wireless-sensor battery (top) incorporates four energy-harvesting chips. A close-up of one chip (bottom) shows a vibrating cantilever that converts mechanical energy into electrical energy.
Credit: MicroGen Systems
MicroGen Systems is developing
energy-harvesting chips designed to power wireless sensors like those used to monitor tire pressure and environmental conditions. The chips convert the energy from environmental vibrations into electricity that’s then used to charge a small battery. The chips could eliminate the need to replace batteries in these devices, which today requires a trip to a mechanic or, for networks of sensors that are widely distributed, a lot of legwork.
The core of MicroGen’s chips is a one-centimeter-squared array of tiny silicon cantilevers that oscillate when the chip is jostled. At the base of the cantilevers is a bit of piezoelectric material: when it’s strained by vibrations, it produces an electrical potential that can be used to generate electrical current. The cantilever array is mounted on top of a postage-stamp-sized, thin-film battery that stores the energy it generates. The current passes from the piezoelectric array through an electrical device that converts the current to a form compatible with the battery. When the chip is shaken by, say, the vibrations of a rotating tire, it can produce about 200 microwatts of power.
MicroGen systems, Inc. is developing a suite of products based on its proprietary piezoelectric vibrational energy harvester (PZEH) technology. These low cost, long lifetime (over 20 years) Micro-ElectroMechanical Systems (MEMS) are micro-power sources that extend rechargeable battery lifetime or will eliminate the need for batteries altogether.