Silicon micromachining technology for sub-nanogram discrete mass resonant biosensors

This paper describes a novel sub-nanogram discrete mass sensor with possible biological applications including potential biomass monitoring of living cells in culture. The sensing element is a micromachined silicon dioxide cantilever fabricated using a process compatible with commercial CMOS microelectronic processes. The 1 μm thick silicon dioxide device consists of two 8 × 150 μm cantilever arms supporting a 50 × 50 μm payload platform. Actuation of this first generation device is performed using a small vibration table. Resonant amplitude are measured by detecting the angular shift of a laser beam incident on the device. Finite element analysis is used to model resonant frequencies, mode shapes, and frequency response. Cantilever resonates in fundamental mode at 15.9 kHz and have an experimental mass sensitivity of 1.9 kHz ng−1.