Flexible Force Sensors Based on Permeability Change in Ultra-Soft Amorphous Wires

A prototype of robust, durable, and reliable force sensor is proposed. The proposed sensor consists of a cylindrical elastic tube, which changes its transversal cross section from circular to elliptical under the influence of the applied force, and a Co-Fe-Si-B ultra-soft magnetic wire-based sensitive element. The sensing element is placed onto the circumference of the elastic tube, being able to detect and measure the deformation produced by an applied force. The impedance of the sensitive element changes when it bends, due to the permeability change when the amorphous wire is subjected to mechanical stress. A voltage proportional to the applied force is picked up at the sensor output by using adapted electronics. The relation between the force and the electrical output signal is determined through calibration. Three different configurations of the sensitive elements distributed around the elastic tube have been analyzed. The developed sensor has an excellent adaptability and an important application potential for medical devices, instrumentation, or other devices which require force feedback.