Stable micro sized electret array produced by localised charging using a silicon shadow mask

A localised corona charging method is presented to produce a micro sized electret array through a shadow mask. It solves low charging efficiency and fast charge decay problems in the micro sized electrets charged by the conventional charging method. The enhancement in the properties of electret is realised by decreasing the electric field gradient causing charge leakage in the dielectric material during charging. Charging efficiency of 93% with 87% of its initial surface potential remained on the localised areas of 50%50%%m after 240 days.