Novel Magnetostrictive Fe-Co-B Thin Film Sensors for Food Safety Detection

As a soft magnetic material with amorphous or nanocrystalline structure, magnetostrictive Fe-Co-B alloy has been considered a potential candidate for high-frequency sensor application. For sensor behavior, high sensitivity and low limit of detection are favored. The smaller the sensor is, the higher the sensitivity it has and the higher the frequency it can achieve. To obtain higher sensitivity, micro scale Fe-Co-B sensors are fabricated with electrochemical deposition and microfabrication. Free-standing Fe-Co-B sensors with a sandwich structure of Au(410 nm)/Fe₅₅Co₂₈B₁₇/Au(130 nm) and an area of 500 μm×100 μm are synthesized. The thickness of the sensors are around 2~10 μm. The magnetostrictive particles show good resonance behavior.  The resonance frequency is about 3 MHz and Q value can be up to 200 in air. The influence of the current density and deposition time on the resonance behavior are investigated. Au/Fe₅₅Co₂₈B₁₇/Au sensor is used to detect Salmonella Typhimurium in dynamic bacteria suspensions. For a 500 μm×100 μm× 7 μm sensor, a limit of detection of 5×10² cfu/ml is achieved with a total peak shift of 103 kHz which are comparable to reported commercial materials. It is very promising to dig out the important role of Fe-Co-B alloy in high-frequency sensors or other micro electronics.