A Self-powered Mems Sensor for Ac Electric Current

A new type of MEMS sensor has been developed for measuring AC electric current. The sensor is comprised of a piezoelectric aluminum nitride MEMS cantilever with a microscale composite permanent magnet mounted to its free end. When placed in proximity to a wire carrying AC current, the alternating magnetic field surrounding the wire induces a sinusoidal force on the sensor magnet, deflecting the piezoelectric cantilever and thus producing a voltage signal proportional to the current in the wire. This sensor does not need to encircle the conductor and its use of piezoelectric materials eliminates the need for a power source. This paper details an improved micromagnet fabrication process using dispenser-printed epoxy and a neodymium alloy magnetic powder. Also presented are the first test results of working MEMS current sensor devices, as well as the development of a fully self-powered sensor package that uses a piezoelectric energy harvester to power circuitry that amplifies the MEMS sensor’s signal.