Electromagnetic microactuators with the electroplated planar coils driven by radial magnetic field

Abstract

In this paper we have proposed, fabricated and tested an electromagnetic microactuator using electroplated copper coil on the p+-silicon diaphragm. The microactuator generates a vertical motion of the diaphragm using the radial component of the magnetic field on the coil plane. In order to guide and concentrate the magnetic field in the radial direction, we propose a new actuator structure with two magnets. In a theoretical study, electromagnetic force is analyzed based on a simplified concentric coil model. Static and dynamic response of the microactuator has been estimated. On this basis, we have designed and fabricated the electromagnetic actuators. In the experimental study, we measure dynamic response of the microactuator for the cases of single magnet and twin magnet compositions. For both cases, the microactuator shows identical values of resonant frequency and quality factor in the ranges of $10.51\pm 0.22$ kHz and $46.6\pm 3.3$, respectively. The twin magnet microactuator generates the maximum peak-to-peak amplitude of 4.4 mm for the AC rms current of 26.8 mA, showing 2.4 times larger amplitude than the single magnet microactuator. For the drive-current in the lower frequency range of 1~5 Hz, the thermal actuation of the microactuator becomes dominant over the electromagnetic actuation. The maximum peak-to-peak amplitude of the thermal actuation is measured as 7.6 mm for the 1 Hz AC rms current of 77.5 mA. The thermal actuation is diminished for the drive current at higher frequency over 10 Hz.