US Patent 9157845 2-D MEMS tribometer with comb drives

A microelectromechanical (MEMS) nanoindenter transducer including a body, a probe coupled to and moveable relative to the body, the probe holding a removeable indenter tip, a first micromachined comb drive and a second micromachined comb drive. The first micromachined comb drive includes an actuator comprising a plurality of electrostatic capacitive actuators configured to drive the probe along a first axis, including in an indentation direction, in response to an applied bias voltage, and a displacement sensor comprising a plurality of differential capacitive sensors having capacitance levels which together are representative of a position of the probe relative to the first axis. The second micromachined comb drive includes an actuator comprising a plurality of electrostatic capacitive actuators configured to drive the probe along a second axis, which is perpendicular to the first axis, in response to an applied bias voltage, and a displacement sensor comprising a plurality of differential capacitive sensors having capacitance levels which together are representative of a position of the probe relative to the second axis. Each of the electrostatic capacitive actuators and the differential capacitive sensors comprises an electrode comb pair, each electrode comb pair including a fixed electrode comb coupled to the body and a moveable electrode comb coupled to the probe.