A MEMS conical spring actuator array

A new MEMS conical spring actuator array is proposed. Previously, we have developed conical spring microactuators having a long stroke (180 μm) in the out-of-plane direction. However, the maximum output force and the packing density were not satisfactory. In the present paper, mechanical and electrical models of a conical spring are described for the calculation of the maximum output force and the driving voltage. Geometrical parameters were optimized using these models and a new geometry for the actuator was derived. The new geometry incorporates a wider and thicker spring that increased the maximum output force from 0.087 mN up to 0.83 mN. The packing density was increased up to 1 actuator/mm² using an additional interconnect layer. In addition, the driving voltage was decreased using a thinner insulating layer. The use of an ac drive prevented the sticking of the actuator during operation. A detailed investigation of the ac drive was also performed.