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Mass sensing of microbeads using a weakly coupled cantilever

Takumi Nakamura, Daichi Endo, Hiroshi Yabuno, Y. Yamamoto, S. Matsumoto
Recently, the measurement of biological molecules using micro cantilever is attracting much interest.
In the measurements as DNA detection with a microcantilever, the mass is generally identified from the eigenfrequency shift in a resonator.
Such a way relies on the frequency response curve under the external or forced excitation and requires a low viscosity environment like air or vacuum.
However, the sensing of biological molecules including the reaction between antibody and antigen needs to be performed in active and the measurement in a liquid environment is essential.
We detect small biological masses in a liquid environment by using a self-excited oscillation produced under the velocity feedback control.
We use a weakly coupled cantilever and carry out a mass sensing based on the change of an amplitude ratio.
We form a gold pattern on one of the cantilevers to fix the biological masses.
We confirmed that the beads are fixed on the cantilever.
Also, we obtained the time history about the amplitude ratio to show the process of the biological reaction of the molecules.
We realized measuring cell order mass from the amplitude ratio.
This study will be improved to the measurement of a much smaller biological mass in a liquid environment.
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