Evaluation of bend sensors for limb motion monitoring

Bend sensors are composed of a flexible substrate and a conductive layer, which changes its electrical resistance with the bending or the angular displacement. They are flexible, light and low-cost devices, usually adopted to measure the human joint motion. For example, bend sensors can be mounted over the elbow, the knee or the finger measuring their angular position. Commercially, different types of bend sensors are available. In this paper, four types of sensor made of a carbon ink-based layer were studied. These sensors differ for the protective layer over the conductive ink. Their electrical resistance also decays over time and depends on how the sensor is fixed on the joint. A preliminary evaluation is reported on this paper. In particular, the behavior of the electrical resistance of the sensors varying the bending angle and the decay of the resistance over time are reported. The goal of this study is to give information about these sensors to the designers in order to increase knowledge for a metrological characterization and to choose the best strategies to design a biomedical device for limb motion monitoring.