SAMs and Protein Adsorption Studies for the Calibration of Miniaturized Quartz Crystal Microbalance Arrays

We report the design and fabrication of a micromachined quartz crystal balance (QCM) array for self assembled monolayers (SAMs) and protein adsorption studies. The microQCM was fabricated using recently developed inductively coupled plasma etching process for quartz to realize resonators with 60 mum thickness and electrode diameters of 0.5 mm. The reduction in the thickness and lateral pixel size has resulted in a sensitivity improvement by factor of 1364 over a commercially available macro-sized QCM. In both rigid and viscoelastic film adsorption limits, we find the microQCM to exhibit three times greater sensitivity than the predicted value when operated at the third overtone. These results show that the micromachined QCM in array format is a very sensitive gravimetric sensor capable of mass resolutions into the femtograms range.