Microelectromechanical ratcheting apparatus

A microelectromechanical (MEM) apparatus formed on a substrate, comprising:

• (a) a ring gear rotatable about an axis and having a plurality of indexing teeth spaced about an inner circumference thereof and a plurality of drive teeth spaced about an outer circumference thereof;
• (b) a rotary thermal actuator formed within the inner circumference of the ring gear and further comprising a plurality of pairs of thermal arms spaced about the axis and extending outward therefrom, with each pair of thermal arms including a hot arm and a cold arm interconnected at an end of each hot arm located distally to the axis, the hot arm thermally expanding to a greater extent than the cold arm in response to a voltage applied across each pair of hot and cold arms, thereby incrementally rotating each pair of thermal arms about the axis;
• and
• (c) at least one pawl operatively connected to each pair of thermal arms and engageable with the ring gear to incrementally rotate the ring gear upon application or removal of the applied voltage.