Nonuniform mass detection using magnetostrictive biosensors operating under multiple harmonic resonance modes

A mechanical resonator made of a freestanding magnetostrictive strip as a mass sensor is used as the sensor platform for the development of biosensors. It is found that these sensors have a Q value in air (similar to 1000) and water (>100). The mass sensitivity of the sensor is strongly dependent on the location of the mass load. For the mass load at node(s), a close to zero sensitivity is obtained. However, for the mass load at the points with the maximum oscillation amplitude, the highest sensitivity is obtained. This highest sensitivity is about twice the sensitivity of the sensor for the mass load uniformly distributed over the sensor surface. Due to the wireless nature and freestanding configuration, both even and odd harmonic modes of resonators can be measured. By using odd and even modes, the blind point issues with the sensors based on mechanical resonators can be overcome. (C) 2010 American Institute of Physics. [doi:10.1063/1.3431523]