The relationship between material properties, device design, and the sensitivity of resonant mechanical sensors

Abstract

In this work we study three distinct resonant micromechanical sensor geometries and their ability to detect the addition of material at different locations on the devices. Small regions of gold were patterned on the resonators, and changes in frequency due to the presence of gold were measured as a function of position, device geometry, and the resonant mode. We have demonstrated the conditions under which micromechanical resonators are sensitive to the mechanical properties of added material as well as its mass and have quantified how these qualities have competing effects on resonant frequency using finite element analysis and analytical techniques. In cases where this competition significantly reduces frequency shift amplitudes, localized binding of the analyte is required, and we will compare different sensor designs and their frequency responses. When material is uniformly added to resonators, however, device geometry has little to no effect on sensitivity. While cantilevers may be the most commonly used geometry in this field, we show that they are not necessarily the most sensitive in all situations. In most biosensing applications, flexural rigidity is not expected to have an impact on resonant frequency, suggesting that all available resonator surface area should be used for analyte binding.