A Novel MEMS Speaker With Peripheral Electrostatic Actuation

We design and fabricate electrostatically actuated micro-speakers with circular diaphragms and peripheral electrode configuration. The novel electrode configuration mitigates the squeeze film damping and increases pull-in voltage when compared with the conventional parallel plate electrostatic transducer design. Finite element analysis shows that under dynamic conditions, we can achieve diaphragm deflections as much as 80 times the gap between the electrodes because of the proposed design. We compare the conventional design of electrostatically actuated audio speakers - where typical electrode separation gaps are around 60 to 100 μm and actuation voltages are in the range of 10 to 200 volts - with the proposed peripheral electrode design with an electrode separation gap of 1 μm and actuation voltage ≤100 volts. The SPL obtained is comparable to the existing designs and ranges from 40 to 60 dB at 1 kHz at 1 cm with different sizes of the micro-speakers. The efficiency achieved with the proposed design is 100
^-4
% at resonance which is at least two orders higher than the typically observed value for electrostatic micro-speakers. [2020-0134]