Venkattraman Ayyaswamy

Direct measurement of field emission current in E-static MEMS structures

Direct experimental evidence of field emission currents in metallic MEMS devices is presented. For the first time, high resolution I–V curves have been demonstrated for micro-gaps in MEMS-based capacitor/switch-like geometries. The I–V dependence shows a good agreement with the Fowler-Nordheim theory, supporting the hypothesis that field emission plays a significant role in charging phenomena in MEMS switches. The data has been used to extract effective values of the field enhancement factor, β, for the metallic structures fabricated under typical MEMS processes.

Near-contact damping model and dynamic response of μ-beams under high-g loads

This paper presents the first near-contact aerodynamic damping model based on rarefied flow modeling for use in dynamic simulations of large-displacement motion and contacting behavior of microbeams. The damping model is constructed based on high-fidelity simulations of rarefied gas flow around microbeams based on the Boltzmann kinetic equation with the Ellipsoidal Statistical Bhatnagar-Gross-Krook (ES-BGK) collision relaxation model. The predictions using the new model and previously published models are compared with experimentally measured responses of silicon microbeams under a high-g dynamic load. The new model is validated by measuring the near-contact behavior of silicon microbeams under loads up to 52,500 g and with ramping rates up to 2,750 g/µs. The model and experiments were found to be in close agreement with a maximum variation of less than 13.1%.

Implementation Challenges and Performance of Forced Harmonic Oscillator Model in Direct Simulation Monte Carlo

The forced harmonic oscillator (FHO) model is an attractive choice for implementation into DSMC due to its higher accuracy over the LarsenBorgnakke (L-B) model, and the fact that it is still an analytic expression. The higher accuracy comes with higher complexity, and several factors which may adversely affect DSMC simulations in particular must be addressed. Detailed balance, round-off errors, and anharmonic oscillator energy limitations, all require some slight modification or cut-off values in the case of the errors in order to ensure its accuracy within DSMC simulations. In addition, quantum jump restrictions to ±5 is shown to reduce the computational time required by as much as 13% while only decreasing accuracy by less than 0.2%. Assessment of the computational resources required for the FHO model in comparison to the commonly used L-B model is performed.