We demonstrate in this letter that variable focus lenses can be realized by pressure-induced deformation of a liquid interface. Large deflections can be achieved by exploiting the capillary pressure barrier generated by high surface tension liquids at the exit of a small well. Modulation of the internal pressure of a liquid interface produces a change in its radius of curvature thus a shift in the plane of focus. Using liquids with high surface tension like water and polymeric low surface energy substrates, liquid-air lenses were realized with a wide focal length tunability (optical power for 2 mm lenses from 130 to 350 diopters). Using the liquid-liquid interface of water and a nonmiscible liquid, pressure-induced tunable lenses were also demonstrated. The application of the lenses in imaging was also shown.
Thin-film microcrystalline diamond micromechanical resonators with mechanical quality factor limited by thermoelastic dissipation in the diamond film are demonstrated. Surface micromachined double ended tuning fork resonators were fabricated from in-situ boron doped microcrystalline diamond films deposited using hot filament chemical vapor deposition. Time-domain thermoreflectance measurements show thermal conductivity of 110 W m À1 K À1 for heat transport through the thickness of the diamond film. Measurement of the quality factor of resonators spanning a frequency range 0.5-10 MHz shows a maximum Q ¼ 81 646 and demonstrates good agreement with quality factor limited by thermoelastic dissipation using 100 W m À1 K À1 for the in-plane thermal conductivity of the diamond film. V
We demonstrate high quality factor thin-film nanocrystalline diamond micromechanical resonators with quality factors limited by thermoelastic damping. Cantilevers, single-anchored and double-anchored double-ended tuning forks, were fabricated from 2.5 μm thick in-situ boron doped nanocrystalline diamond films deposited using hot filament chemical vapor deposition. Thermal conductivity measured by time-domain thermoreflectance resulted in 24 ± 3 W m−1 K−1 for heat transport through the thickness of the diamond film. The resonant frequencies of the fabricated resonators were 46 kHz–8 MHz and showed a maximum measured Q ≈ 86 000 at fn = 46.849 kHz. The measured Q-factors are shown to be in good agreement with the limit imposed by thermoelastic dissipation calculated using the measured thermal conductivity. The mechanical properties extracted from resonant frequency measurements indicate a Young's elastic modulus of ≈788 GPa, close to that of microcrystalline diamond.
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