Mass sensing with resonating ultrathin double beams

This paper reports on mass sensing with 33-nm-thick single crystalline cantilevers by a double-beam laser Doppler vibrometer. The resonant frequency of an oscillating thin cantilever beam is very sensitive to a loaded mass. However, the drift of the resonance, due to gas adsorption and mechanical instability, limits the minimum detectable mass in general. Two cantilevers for sensing and its reference will be compensate their influences. Two cantilevers were self-oscillated by electrostatic actuation at a different resonant frequency. On the end of one cantilever, a 10-pico-g sample (a particle of organosilicon monomer) was mounted, and thermogravimetry of the sample using the two cantilevers was demonstrated. The cantilevers were heated up by a heater in vacuum, and the mass change was detected from the change of its resonant frequency. Exact temperature change can be estimated from the resonant frequency change of the reference cantilever. The derivative of the frequency change, corresponding to desorbed mass, clearly shows a peak at about 370°C.