  Microelectromechanical systems (MEMS) that require contact of moving parts to
implement complex functions exhibit limits to their performance and
reliability. Here, we advance our particle tracking method to measure MEMS
motion in operando at nanometer, microradian, and millisecond scales. We test a
torsional ratcheting actuator and observe dynamic behavior ranging from nearly
perfect repeatability, to transient feedback and stiction, to terminal failure.
This new measurement capability will help to understand and improve MEMS
motion.
