Aveek Nath Chatterjee

A novel approach to the analysis of squeezed-film air damping in microelectromechanical systems

Squeezed-film damping (SFD) is a phenomenon that significantly affects the performance of micro-electro-mechanical systems (MEMS). The total damping force in MEMS mainly include the viscous damping force and elastic damping force. Quality factor (Q factor) is usually used to evaluate the damping in MEMS. In this work, we measure the Q factor of a resonator through experiments in a wide range of pressure levels. In fact, experimental characterizations of MEMS have some limitations because it is difficult to conduct experiments at very high vacuum and also hard to differentiate the damping mechanisms from the overall Q factor measurements. On the other hand, classical theoretical analysis of SFD is restricted to strong assumptions and simple geometries. In this paper, a novel numerical approach, which is based on lattice Boltzmann simulations, is proposed to investigate SFD in MEMS. Our method considers the dynamics of squeezed air flow as well as fluid-solid interactions in MEMS. It is demonstrated that Q factor can be directly predicted by numerical simulation, and our simulation results agree well with experimental data. Factors that influence SFD, such as pressure, oscillating amplitude, and driving frequency, are investigated separately. Furthermore, viscous damping and elastic damping forces are quantitatively compared based on comprehensive simulation. The proposed numerical approach as well as experimental characterization enables us to reveal the insightful physics of squeezed-film air damping in MEMS.

A novel squeezed-film damping model for MEMS comb structures

We present the implementation and validation of a novel model for simulating comb squeezed-film damping. The model is computationally efficient regardless of finger count and optionally includes top and bottom encapsulation surfaces surrounding the fingers. Comparison with standard numerical simulation shows a difference in damping coefficient of less than 1%. One application is to predict the Q factors of resonant MEMS such as gyroscopes for which a high Q-factor ensures stable oscillations and certain magnetometers for which it amplifies the sensitivity. The model is validated against experimental Q factors of a magnetometer, predicted values are within 10% of measurement from 0.01MPa to 100Pa.

Analysis of squeeze film air damping in MEMS with lattice Boltzmann method

Squeeze film air damping has significant impact on the performance of microelectromechanical devices. In order to understand the squeezed-film damping mechanism, Reynolds equation and its derivatives have been used in previous studies. In fact, the Reynolds equation has limitations in quantifying MEMS characteristics because its assumptions on small amplitude and non-slip boundary condition may not be satisfied in practice. Advanced modeling approaches should be considered to capture detailed energy dissipation physics. In this paper, we study the squeeze film air damping in MEMS using lattice Boltzmann method, which is derived from classical Boltzmann transport equation. Our major focus is to reveal how the air film is squeezed by the side movement of a comb structure. By considering the slippage and amplitude effect, direct lattice Boltzmann simulations are performed to obtain the Q factor. Viscous damping and elastic damping, two contributors to the energy loss, are quantitatively compared to reveal the dominant damping mechanism.