High-Accuracy Digital-to-Analog Actuators Using Parallel Spring Array

We present a high-accuracy micromechanical digital-to-analog (DA) actuator using parallel interconnection of identical springs. The parallel DA actuator achieves a high-accuracy cascaded actuation because it is independent of spring variation caused by fabrication error. We design the parallel DA actuator using 4-bit digital actuators, whose four different unit displacement of x₁=7.0 mum, x₂=5.8 mum, x3=4.8 mum, and x4=4.0 mum are designed to make the output displacement linear for the output range of 0~5.4 mum. In experimental study, the output range and nonlinearity are measured as 0~4.7 mum and 8.65%, respectively. The parallel DA actuator generates the output displacement with the accuracy of 0.29 plusmn 0.20 mum and the precision of 20.4 + 5.8 nm. We experimentally verify the positioning capability of the present parallel DA actuator is suitable for high-accuracy optical manipulation.