Design and fabrication of acoustic wave actuated microgenerator for portable electronic devices

An acoustic wave actuated microgenerator for power system applications in mobile phone was design, fabricated, and characterized. We used the acoustic wave of human voices or speakerphone by way of an electromagnetic transducer to produce electrical power for charging or to run a portable electronic device. The proposed microgenerator is composed of a planar coil, a suspension plate with supporting beams and a permanent magnet. In this paper, the dynamic response of the suspension structure and the variation of the induced magnetic flux were characterized by using commercial finite element analysis and Ansoft Maxwell EM3D software, respectively. The electroplating nickel and silicon bulk micromachining techniques were used to fabricate the suspension plate and planar coil, and by integrating a permanent magnet as well as wafer to wafer adhesion bonding to accomplish the microgenerator assembly. The experimental results shown the typical microgenerator with a planar dimension of 3 mm times 3 mm, the maximum induce-voltage 0.24 mV was generated at the driving frequency of 470 Hz. The dynamic response of microgenerator can be designed to meet a specific acoustic driving frequency to increase the efficiency of energy harvesting.