Biosensors based on flexural mode piezo-diaphragm

This paper presents a mass sensitive biosensor utilizing a flexural vibration mode of a micromachined piezoelectric micro-diaphragm. The mass sensitivity of the diaphragm has been investigated with respect to the vibration modes. Theoretical analysis reveals that, for the same multilayer structure, the mass sensitivity is mainly determined by the mass per unit area of the diaphragm, the flexural mode sensor can work at a lower operating frequency than thickness mode without losing its mass sensitivity-about 30 times higher than that of a QCM. A biosensor with Q value of more than 200 has been demonstrated at a resonant frequency of as low as 120 kHz. Frequency shift in response to captured goat IgG on sensor surface has been detected. These results indicate that the flexural mode micromachined diaphragm has a potential to be an alternative to the low-cost QCM biosensors.