Sensing of Body Movement by Stretchable Triboelectric Embroidery Aimed at Healthcare and Sports Activity Monitoring

Abstract

: In this work, we introduced an embroidery-based stretchable (up to 60–70%) triboelectric nano-generator that could be attached to different parts of the human body such as fingers, knee, elbow, back, or shoulders, to sense the body movement. It can be used as activity recognition for health care and sport activity monitoring. The sensor was composed of different yarns embroidered on a stretchable conductive substrate, allowing it to sense diverse mechanical deformation of different body parts. Different stitching styles, patterns, stitch lengths, and shapes have been selected to cater to the unidirectional, bidirectional, and multidirectional force and obtain the maximum movement flexibility. In order to do embroidery on a stretchable substrate, a non-stretchable water-soluble second substrate has been added before embroidering, and is afterwards removed by application of steam. A sample of 1.5 × 6 cm 2 was used for sensing finger movement and generated a peak to peak voltage of 274.5 mV. The amount of generated voltage depended upon the application area on the body and its deformation, thread type, stitch type, stitch length, and shape of embroidery. A stitch length of more than 2 mm with a line density of 1 line per mm resulted in a stretchable sample. The state of the art of the developed sensors is their low price, flexibility, and low weight. They are all obtained with commercially available embroidery yarns and commercially available technology for their development.