The aim of this work was to determine the constant of elasticity for a static silicon micromechanical structure with a given, shape, having its width and length in the hundreds of micrometers range and its thickness in the micrometer domain, subject to torsion. This is done by experimentally studying the torsion vibration of the structure. On this purpose, test structures have been manufactured, with thickness varying in a certain domain. Special alignment marks have been used in order to align the structures with respect to the crystallographic directions of the silicon. The structures have been activated with acoustic waves. The resonance frequency in the torsion mode has been measured by means of an optical set-up. Successive measurements and etch-thinning of the structures provided the dependency of the resonant frequency on the structure thickness. A theoretical formula expressing the resonance frequency fr in terms of the shear modulus G, thickness e, and damping coefficient $gamma has been fitted with the experimental points in order to obtain the values of G and g. The proportionality factor k between the activation force and the angular or linear displacement has been calculated in terms of mechanical engineering. Considerations regarding the bending phenomenon complete the strategy to determine the constant of elasticity for arbitrary structures.
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