An alternative solution to improve sensitivity of resonant microcantilever chemical sensors:: comparison between using high-order modes and reducing dimensions

By measuring shifts in the resonant frequency of a silicon microcantilever coated with a sensitive layer, it is possible to obtain a competitive chemical microsensor. In fact, the sensitivity of such a microsensor is improved when used in high resonant frequency device. Usually, to increase the resonant frequency, smaller microcantilevers are used. The limitation on increasing the natural frequency by reducing the microstructure size is often due to the limitation of the deflection measurement principle. Furthermore, it could also be difficult to obtain reproducible sensitive coatings on very small surfaces. In order to achieve high sensitivities corresponding to high frequencies without decreasing the microstructure size, high-order flexural modes can be considered. In this paper, it is demonstrated that the theoretical performance of the resonant microcantilever chemical sensor is essentially due to the resonant frequency value and not due to the mode order. The advantages of increasing the resonant frequency by using high-order modes is also confirmed experimentally. (c) 2004 Elsevier B.V. All rights reserved.