Optimization of an electromagnetic comb drive actuator

We present the first electromagnetic comb drive actuator which allows for over 100 μm of linear actuator motion at large air gap widths of 25 μm at 300 coil windings, a structural height of 400 μm and for an applied current of 8 mA. Previously reported designs require very narrow air gaps of 3 μm at structural heights of up to 1 mm [K. Fischer, H. Guckel, Long throw linear magnetic actuators stackable to one millimeter of structural height, Microsyst. Technol., 4 (1998) 180–183] which makes them sensitive to operate, and challenging to fabricate. The new design reduces the reluctance by a parallel connection and cascading of several pole shoes as is well known for electrostatic actuators. This reduces the current consumption and linearizes the current–displacement characteristic. The cascaded design further enhances the displacement range at the cost of a slightly increased current consumption at the onset of the stroke. To analyze the influence of the number of air gaps on the plunger motion the total cross-sectional area of the magnetic core is kept constant while the number of air gaps is varied. Magnetic and mechanical material properties are measured for an accurate simulation of the system behavior. Experimental results confirm the theoretical predictions.