Magnetostrictive resonators as sensors and actuators

Two types of magnetostrictive resonators – magnetostrictive microcantilever (MSMC) and magnetostrictive particle (MSP) – have been introduced as sensor platforms. Their principles and advantages as sensor platforms are discussed along with the materials selection. A detailed and complete comparison between the MSMC and MSP is given. It is concluded that for the resonators with the same size, an MSP exhibits a higher sensitivity and has a much higher resonant frequency. For the resonators with the same resonant frequency, MSMCs exhibit a much higher sensitivity and have a much smaller size than MSPs. Using antibody as the sensing element, MSP biosensors for in situ detection of Escherichia coli and Listeria monocytogenes are developed and characterized. These biosensors exhibit a high performance. For example, the MSP-antibody biosensors of 1 mm × 0.3 mm × 15 μm exhibit a detection limit less than 100 cfu/ml for in situ detection of bacterial cell in water. A new type actuator is introduced using MSPs. The MSP actuator is operated using AC magnetic field with a frequency close to, but different than, its resonant frequency. The MSP actuator exhibits an unlimited displacement, and its moving direction is controlled by the operating frequency used.