Cantilever-based mass sensor using high order resonances for liquid environment

For precisely measuring the mass variation, different modes of cantilever-based mass sensor were developed. The dynamic mode applied for mass sensor has advantages of less thermal drift and high mass sensitivity. However, mass sensor is usually operated in liquid environment for bio-chemical examination, but the liquid viscosity significantly dampens the performance of the dynamic mode. In this paper, the high order resonances are proposed for increasing the mass sensitivity in liquid. For comprehending the influence on the mass sensitivity, we analytically and experimentally studied the performances of the unmodified commercial cantilever the modified cantilever, which is made of commercial cantilever and processed to derive different shapes with mass variation. And in their thermal fluctuation spectra, the first five order resonances are detected for comparison. The mass sensitivity -5.397 Hz/pg of the fifth order resonance is 94 times that of the first order resonance of -0.057 Hz/pg.