Theoretical Analysis of Dynamically Operating Polymer-Coated Microcantilever Chemical Sensors in a Viscous Liquid Medium

The generalized characteristics of dynamically-drjven, polymer-coated microcantilever (bio) chemical sensors in a viscous liquid medium are obtained. The effects of the polymer coating and the viscous liquid medium are used with standard beam theory to derive a generalized equation of motion for the device. This generalized equation of motion can be used to find generalized expressions for the resonant frequency and the quality factor of the dynamically-driven, polymer-coated microcantilever (bio) chemical sensor. With these generalized expressions, the effects of analyte-induced coating plasticization, swelling, and changes in the viscous liquid medium are investigated. These generalized expressions can also be simplified to previously derived expressions obtained in the literature using particular assumptions placed on the medium and/or coating. It is commonly assumed that shifts in the resonant frequency are a function of only the sorbed analyte mass. However, it is shown in the present work that other changes in the medium and coating properties can significantly affect the microcantilever\u27s response. The predicted resonant frequency shifts using the generalized expression for the resonant frequency are compared to available experimental data and the effects of plasticization are analyzed