A monolithic micro four-bar mechanism was fabricated in silicon to examine motion amplification as well as the effect of non-ideal geometric profiles in its flexure hinges. Through-wafer deep reactive ion etching (DRIE) was used to produce high-aspect-ratio flexure joints that allow compliant motion within the plane of a silicon wafer. The flexures were approximately 20 microns wide and 530 microns deep, micromachined through the entire wafer thickness. A taper angle of approximately 0.5 degree narrowing toward the bottom of the wafer was measured in the flexure cross section. A finite element model was developed to predict the output rotation of one link in response to the displacement applied at the drive link. For a 1-micron linear input, the model predicted a 0.39-degree angular displacement for the output link. This showed close agreement with experimental data that measured 0.41 degree. An enhanced finite element model that accounted for the tapered cross-section, however, predicted a slightly smaller input/output relation of 0.37 degree per micron.

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