COMB ACTUATORS FOR XY-MICROSTAGES

The flexibility of the suspension is a key factor if the driving voltage of electrostatic micro comb actuators is to be reduced. We have fabricated and tested surface micromachined polysilicon comb actuators with submicrometre-wide suspensions. For example, a comb actuator with a folded beam suspension consisting of 0.4 mum wide, 2 mum thick and 300 mum long beams allowed for a small spring constant around 6 mN/m. As a result, only low voltages are required for actuation, e.g., 14.5 V for a 7.3 mum displacement. In addition, we have constructed and characterized a novel actuator, named the sarcomere actuator, where several comb actuators are placed in parallel; it allows the driving force at a given voltage to be increased by almost a factor of three. Based on the high flexibility of the suspension, we have fabricated a comb-driven xy-microstage. Tests with this prototype device show that controlled two-dimensional positioning in the range of several micrometres and with a precision of better than 80 nm can be achieved.