Digital tuning of the quality factor of micromechanical resonant biological detectors

We present a new technique to increase the quality factor of micro-nanomechanicl oscillators using digital electronics. The mechanical oscillator is set into oscillation by using a single driving force whose amplitude depends on the amplitude and phase shift of the oscillation. Experiments performed with microcantilevers in air and aqueous solution show that the quality factor can be increased about two orders of magnitude. This technique is applied for the measurement of the viscosity change of an aqueous solution due to the presence of proteins.