Mechanical Characterization of Micromachined Glass-Blown 3-D Spherical Shells

This paper reports a non-contact experimental characterization of resonant modes in micromachined spherical shells fabricated by pressure and surface tension driven plastic deformation (glassblowing). For a glass-blown shell with 0.9 mm diameter and 10 μm average thickness, dynamically balanced 4and 6-node vibratory modes were identified at 1.27 MHz and 1.44 MHz, respectively. Without any trimming or tuning of natural frequencies, the relative frequency mismatch ∆f/f for the 4and 6-node vibratory modes was measured as 0.63% and 0.2%, respectively, on par with the state-of-the-art planar silicon MEMS. Glass-blown shells as resonant elements may enable new architectures of vibratory 3-D MEMS for high-g environments.