Resonance behavior of magnetostrictive micro/milli-cantilever and its application as a biosensor

Magnetostrictive micro/milli-cantilever (MSMC) was recently introduced as a promised biosensor platform due to its high performance in liquid and wireless nature. To better understand the resonance behavior of the MSMC, unimorph-type MSMCs with thickness about 30 μm and different lengths and widths were fabricated, and their resonance behaviors were investigated in air and in different liquids. The influence of the driving magnetic fields and the surrounding media on their resonance behavior was also studied. It is found that the amplitude of the driving ac magnetic field has very weak influence on the resonance frequency. On the basis of the damping effect of different liquids on the resonance behavior of the MSMCs, it is found that the characteristic frequency of the MSMC is linearly dependent on the density of the liquid media, while the Q value is inversely proportional to the square root of the product of the density and viscosity of the liquid media. It is also found that the damping effect of liquid on the MSMC can be treated as a damping string of sphere and the effect radius of the oscillating sphere for an MSMC is a constant. The value of the effect radius for different MSMCs was experimentally determined. Additionally, the resonance frequency of the MSMC is very stable. Due to their wireless nature, MSMCs are suitable for the development of a cantilever array. It is experimentally demonstrated that the characterization of an MSMC array is as simple as a single MSMC. The detection of Bacillus anthracis spores in water was performed using MSMC biosensors in a real-time manner to demonstrate the in situ detection capability.