Electrode optimization of an electret-based vibration generator in slot-effect configuration

This paper offers insights into optimization of electret-based energy harvesters made of two patterned electrodes facing movable electret strips parallelized with a pitch p. The effective electrode dimension of such harvester structures is optimized to maximize power under given displacement amplitude and acceleration amplitude, while the length and the width of the design area are kept fixed. The geometrical optimization includes fringing field effects that may have significant impacts on the output power of the small-scale devices. The optimization problem is carried out through an established accurate lump-model represented by an equivalent circuit. The optimal electrode width that gives maximum power is proportional to the proof-mass displacement amplitude by an approximate formula a(opt) approximate to 1.45X(0). Optimizing the pitch can further increase the maximum power as it simultaneously regulates both optimal ratios to the electrode width and the gap size.