A microcantilever chemical sensors optimization by taking into account losses

Abstract

The current trend in increasing microcantilever resonant frequencies leads to relatively low quality factors for microcantilevers resonating in a gas medium. In order to increase the quality factor of such high-frequency microcantilevers, an approach that takes into account the different types of losses is provided to specify appropriate values of microcantilever aspect ratios (length to thickness, width to thickness). Conventional values of aspect ratios result in low quality factors, while those proposed here lead to slightly higher values of quality factor.

Effect of Coating Viscoelasticity on Quality Factor and Limit of Detection of Microcantilever Chemical Sensors

“…In the case of chemical sensors, the surrounding medium is usually either a gas at atmospheric pressure or a liquid. Consequently, without the sensitive coating, the dominant losses are due to viscous damping, [18]. The principal aim of this paper is to understand the modification of the total quality factor when a sensitive coating is added.…”

“…In fact, for a given amplifier, the frequency noise is essentially due to the variation of the amplifier phase . According to the Barkhausen condition, which is satisfied in all oscillators, the frequency noise, , can be expressed with a first-order limited development (small phase variations) (18) The expression of the phase of the micromechanical resonator near the resonant frequency allows one to obtain the expression of the oscillator stability, , as a function of the resonant frequency and quality factor [25] ( 19) As in the case of intrinsic noise, the frequency fluctuation can be used to relate the LOD to : Expression (20) may be used to determine the optimum sensitive coating thickness for minimum LOD. The case of a PIB coating on a silicon microcantilever m m m is presented in Fig.…”

Resonant characteristics of rectangular hammerhead microcantilevers vibrating laterally in viscous liquid media

“…For this reason, several recent studies have measured and modeled the Q-factors of cantilevers vibrating in out-ofplane bending modes in air. [4][5][6][7][8] While Q-factors up to 1500 have been measured for the first out-of-plane bending mode in air, 4 liquid operation becomes challenging because of the substantial viscous damping by the fluid. Besides low Q-factors, typically not exceeding 10-20 in water, 2 a substantial reduction of the out-of-plane resonance frequency (typically in the range of 30-50%) is observed in liquid due to the large effective mass of the fluid.…”

Geometrical considerations for the design of liquid-phase biochemical sensors using a cantilever's fundamental in-plane mode

“…The frequency stability is correlated with the quality factor, Q, of the resonance mode. For this reason, several recent studies have measured and modeled the Q-factors of cantilevers vibrating in out-ofplane bending modes in air [4], [5], [6], [7] and [8]. While Q-factors up to 1500 have been measured for the first out-of-plane bending mode in air [4], liquid operation becomes challenging because of the substantial viscous damping by the fluid.…”