Stochastic dynamics of micron-scale doubly clamped beams in a viscous fluid

Nanofluidics of Single-Crystal Diamond Nanomechanical Resonators

Single-crystal diamond nanomechanical resonators are being developed for countless applications. A number of these applications require that the resonator be operated in a fluid, that is, a gas or a liquid. Here, we investigate the fluid dynamics of single-crystal diamond nanomechanical resonators in the form of nanocantilevers. First, we measure the pressure-dependent dissipation of diamond nanocantilevers with different linear dimensions and frequencies in three gases, He, N2, and Ar. We observe that a subtle interplay between the length scale and the frequency governs the scaling of the fluidic dissipation. Second, we obtain a comparison of the surface accommodation of different gases on the diamond surface by analyzing the dissipation in the molecular flow regime. Finally, we measure the thermal fluctuations of the nanocantilevers in water and compare the observed dissipation and frequency shifts with theoretical predictions. These findings set the stage for developing diamond nanomechanical resonators operable in fluids.

Thermoelastic damping in optical waveguide resonators with the bolometric effect

Incorporating the bolometric effect, the thermoelastic damping in a nanowaveguide resonator driven by an optical gradient force is investigated in this paper. Based on the Euler-Bernoulli beam theory, the governing equation of the optowaveguide resonator is derived by considering the complex distribution of injected optical power, which has significant influence on the thermoelastic damping. By solving the heat diffusion equation, the theoretical model of the thermoelastic damping is presented. In this model, the effects of injected optical power, representative temperatures, waveguide material, and geometries on the thermoelastic damping are studied and discussed respectively. The results show that the peak value of thermoelastic damping increases as the injected optical power is increasing within a low range. Hardly any changes exist for the intrinsic energy dissipation of different materials at higher injected optical power. When the environmental temperature falls in the range of 293-500 K, the thermoelastic damping increases slowly, and then drops down quickly as a function of the dimensionless frequency. However, the thermoelastic damping monotonically decreases when the representative temperature drops to lower than 293 K. In addition, the thermoelastic damping is found to be scale dependent, particularly with the effect of injected optical power.