Mass sensing using a functionalized subordinate oscillator array

Vibrometric based mass sensing for detection of trace levels of chemical vapors has been under investigation for a number of years. One implementation of such a sensor uses a vibrating MEMS cantilever that has been functionalized to bind with a specific chemical compound. The additional mass reduces the resonance frequency of the structure by an amount that can be related to the concentration of the compound. This work describes an analytic and numerical study of an array of differently functionalized cantilevers coupled to a primary structure. The dimensions of individual cantilevers are chosen such that there is a distribution of their isolated natural frequencies and the mass of the primary structure is substantially larger than the collective mass of the subordinate cantilevers. The isolated natural frequencies of the cantilevers must be packed around that of the primary structure such that the response curves of neighboring cantilevers cross near their half power points. This overlap ensures an exchange of energy between array elements. Results describing optimized distributions of cantilever properties will be presented. Both fabrication variations and the sensed mass are considered as disorder in the system. This presentation reports how the relative magnitude of these disorders affects mass declarations.