Microdiaphragm resonating biosensors in higher frequency modes

Influences of different vibration modes of microdiaphragm resonating biosensors on their detecting capability are investigated in this paper. In order to study the mass sensing capability of the sensor, gold layers with different thicknesses are deposited on the sensor's surface. The frequency shift due to this mass deposition in different frequency modes is measured. An increase in the sensitivity and the quality factor (Q-factor) is found with the increase in the vibration mode number of the sensor. The experimental results demonstrate that the mass sensitivity and quality factor of the device are 4.08 Hz/ng and 241.80 at the ninth mode. These are 2.76 and 10.26 times higher than the mass sensitivity and the Q-factor of the device at the first mode. The observations lead to this conclusion that the sensitivity of microdiaphragm resonating biosensors can be increased by working in higher modes without changing their physical parameters.