Modeling of a tuning fork biosensor based on the excitation of one particular resonance mode

The use of electrostatically driven silicon double-ended tuning forks as sensors for biological applications is theoretically demonstrated. The sensing principle proposed is that added mass or stiffness arising from the binding of biomolecules onto the surface of one tine of the tuning fork leads to a mismatch of the two tines while exciting the 'in phase' resonant mode which will be the qualitative signature of the biomolecular recognition. Theoretical considerations are introduced to analyse the dynamic behavior of the tuning fork and give clear design rules allowing us to avoid mechanical nonlinearities which could noticeably affect the response of the sensor. Then, a simple mass–spring equivalent model is set up to explain the response of a perfectly matched double-ended tuning fork and the theoretical response of the tuning fork to a perturbation (mass and/or stiffness loading on either tine) is investigated.