Abstract
The shear-vibration resonance frequency of an AT-cut quartz crystal shows ultrahigh temperature stability on the order of 1 ppm/K. When molecules are captured on the oscillator surface, the resonance frequency decreases because of the mass-loading effect. Because the shear vibrational mode allows vibration even inside a liquid, the AT-cut quartz resonator has been adopted for biosensors. It has been recognized that the mass sensitivity significantly increases upon thinning the oscillator, but achieving this has never been straightforward because of the heavy electrodes and wires attached directly on the surfaces. We thus developed wireless-electrodeless quartz-crystal-microbalance (QCM) biosensors; instead of electrodes, we used antennas for noncontact measurement of the resonance frequency and achieved significantly improved mass sensitivity. Here, I introduce the principle and configurations of the wireless-electrodeless QCMs, including the MEMS process for mass production.
