Microgimbal torsion beam design using open, thin-walled cross sections

A thin-film micromolding process enabled the construction of microtorsional springs with unique cross-sectional designs by combining high-aspect-ratio beams with horizontal surface features. Cross sections such as T-bars, pi sections, and channels were utilized in creating torsional springs with low torsional stiffnesses and high in- and out-of-plane bending stiffnesses. E xperimental modal analysis was used to determine torsional stiffnesses as l ow as 0.13 muN-m/deg with T-bar springs 45 mum tall, 50 mum wide, and 100 m um long. Springs of the same outer dimensions but with solid rectangular cr oss sections were calculated to have torsional stiffnesses of at least two orders of magnitude greater. Several microgimbals were constructed using th e thin-film micromolding process with various torsional spring designs. Mod al analysis was used to experimentally determine pitch and roll natural fre quencies. Torsional stiffness models for open, thin-walled sections that in cluded warping effects were developed and used to analytically predict the torsional natural frequencies of tested spring designs to within +/- 20%.