A Wireless, Passive Magnetoelastic Force–Mapping System for Biomedical Applications

A wireless, passive force–mapping system based on changes in magnetic permeability of soft, amorphous Metglas 2826MB strips is presented for long-term force/stress monitoring on biomedical devices. The presented technology is demonstrated for use in lower-limb prosthetics to ensure proper postoperative fitting by providing real-time monitoring of the force distribution at the body-prosthesis interface. The sensor system consisted of a force-sensitive magnetoelastic sensing strip array that monitored applied loading as an observed change in the peak amplitude of the measured magnetic higher-order harmonic signal of each array element. The change in higher-order harmonic signal is caused by the change in the magnetic permeability of the sensing strips that corresponds to an increase in strip magnetization. After loading, the measured higher-order harmonic signals were fed into an algorithm to determine the applied forces, allowing for determination of the real-time loading profile at the body prosthesis interface.