Wireless Stress Sensor Based on Magnetic Microwires

Abstract

The development of wireless sensors and biosensors is a topic of great current interest. Amorphous magnetoelastic microwires are perfect candidates to be used as sensing elements based on two important properties, that is, magnetoelastic resonance and high-frequency giant magnetoimpedance. It was observed that such microwires present the key feature of performing magnetoelastic resonance, at the kHz range of frequency, in the absence of applied field. This fact, in addition to their small size, gives the microwires unique advantages over the widespread ribbons, currently in use as magnetoelastic sensors. The frequency, amplitude, and damping of the vibration give information of the sensor environment. On the other side, the microwire reflectivity in the microwave range can be modulated by means of magnetoimpedance effect. The maximum-induced electric current, as well as the maximum ac modulation, occurs for frequencies determined by the micro- wire length. The modulation also varies as a function of the dc-applied field and applied stress.