Piezoresistive Polymer-Based Materials for Real-Time Assessment of the Stump/Socket Interface Pressure in Lower Limb Amputees

This paper reports a suitable piezoresistive carbon nanotube (CNT)/PVDF composite capable of measuring the interface pressure within prosthetic stump/sockets. The transducers were prepared by hot pressing with CNTs with sample concentrations up to 10 wt.%. The sensibility (Gauge factor) of the composites was characterized using a mechanical testing equipment and the values reached 6.2. After the optimization of the materials, tests were conducted with a prototype placed in lower limb amputee patients, performing several standing and walking protocols. The prototype was tested in four lower limb amputees using a CNT concentration of 2 wt.% within the PVDF matrix. The transducers were fabricated with dimensions of $10\times25$ mm $^{2}$ and ~1 mm of thickness functionalized with Ti–Ag thin-film electrodes at the surface. To acquire the electrical signal, an electronic circuit was developed with a wireless data acquisition system. The results suggest a strong application potential of the developed sensor prototype, namely as a complementary diagnostic tool, supporting socket design and rectification, being therefore an effective mean to increase patients’ quality of life.