High power LIGA wobble motors for arterial plaque removal

The construction of a LIGA fabricated actuator is shown. Rotor positional information is provided by segmenting the bearing, where the momentary continuity between adjacent segments is detected as the rotor rolls around the perimeter of the bearing. To minimise the number of additional connections, the bearing segments are connected in two sets, with adjacent segments in different sets. Given a known starting position, the rotor motion can therefore be tracked. Using this method, the actuator can be excited with synchronous signals without introducing excessive complexity to the actuator or controller. The prototype devices are 300 microns tall with the rotor and stator fabricated separately and assembled manually. The stator outside diameter is 2600 microns and gear ratios of 228 and 114 and minimum rotor stator air gaps of 5 and 10 microns have been produced. A patterned sacrificial titanium layer was used to create undercuts to pass the connections from contact pads to the bearing segments and the inner stator