Fabric tactile sensor composed of ball-shaped umbonal fibre for detecting normal and lateral force

The authors previously proposed an artificial hollow fibre for use as a microelectromechanical systems (MEMS) material to produce a wearable sensing system and developed a fabric tactile sensor to apply to it. In this Letter, the authors developed a ball-shaped projection for producing the umbonal fibre to improve sensing performance for normal- and lateral-forces detection. An adhesive was manually dropped on the fibre to form the ball-shaped projection structure by surface tension. Its typical diameter was 1.0 mm. The entire surface of the umbonal fibre was then coated with metal and insulation layers. Finally, the umbonal hollow fibre, two weft hollow fibres, a brass wire and cotton yarn were woven together to produce the fabric tactile sensor. The sensor output linearly increased with the increase in applied normal force because of the ball-shaped projection. The sensor output obtained from the two weft fibres increased with the increase of the applied lateral force. It also demonstrated excellent repeatability.