Measuring muscle movements for human interfaces using a flexible piezoelectric thin film sensor

This paper proposes a novel method to measure muscle movements for human interfaces. During muscle movements, cross-sectional muscle area changes, and this can be detected at the skin surface. In this study, a flexible piezoelectric thin film sensor is used to measure the morphological change of the skin surface. This sensor is made of oriented aluminum nitride (AlN) thin film, and the total thickness is less than 40 μm. Since the AlN film sensor has good sensitivity, small strain of the skin surface can be measured. Furthermore, a motion classification method is developed to investigate the potential of the proposed sensor for its use in human interfaces. Response characteristics of the AlN sensor were tested with experiments using a cantilever beam. In addition, motion classification experiments were conducted with five subjects, including a patient with cervical spine injury. The experimental results validate the effectiveness of the proposed method.