Peter Fonda

Hemispherical wineglass resonators fabricated from the microcrystalline diamond

We present the development of millimeter scale 3D hemispherical shell resonators fabricated from the polycrystalline diamond, a material with low thermoelastic damping and very high stiffness. These hemispherical wineglass resonators with 1.1 mm diameter are fabricated through a combination of micro-electro discharge machining (EDM) and silicon micromachining techniques. Using piezoelectric and electrostatic excitation and optical vibration measurement, the elliptical wineglass vibration mode is determined to be at 18.321 kHz, with the two degenerate wineglass modes having a relative frequency mismatch of 0.03%. A study on the effect of the size and misalignment of the anchor and resonator’s radius variation on both the average frequency and frequency mismatch of the 2θ elliptical vibration modes is carried out. It is shown that the absolute frequency of a wineglass resonator will increase with the anchor size. It is also demonstrated that the fourth harmonic of radius variation is linearly related to the frequency mismatch. (Some figures may appear in colour only in the online journal)

Micromachining 3D hemispherical features in silicon via micro-EDM

This paper presents an investigation of micro electrical discharge machining (μEDM) as a viable method for micromachining 3D shapes in silicon. The approach integrates a two-step μEDM process with standard silicon microfabrication techniques to create smooth and axisymmetric 3D hemispherical structures with eccentricity, ε ~ 0.11 and a radius variation <; 2%. Through the selection of ultrahard polycrystalline diamond as the μEDM electrode, the low tool wear allows for high throughput machining of 200 wells in silicon within a short total processing time of 80 min. Feasibility of the approach is demonstrated in the fabrication of millimeter scale hemispherical shell structures using the machined silicon features as a mold.