Spray Coated Piezoresistive Bend Sensor for Controlled Movements in Soft Robots

This work presents a flexible piezoresistive sensor for measuring the bending angles to facilitate controlled movements in soft robots. The sensors was realized using a piezoresistive sensing material prepared by mixing graphite in a polyvinylidene fluoride (PVDF) solution. The resultant graphite solution was spray-coated on a ~80µ-thick polyvinylchloride (PVC) substrate to realize a 5 x 5cm- wide piezoresistive film. Three similar sensors (~3mm x 30mm in dimension) were realized and their performance compared. The results obtained show a change in resistance ΔR/RO ~80% for a bending angle of 50o and a sensitivity of ~ ΔR/Ro = 1.5% per degree bending. The sensor makes it possible to measure in real-time the bending of soft and flexible robot as it can uniquely detect the bending conditions. Hence, the sensing information from the sensor could be used for a close loop control of their locomotion or reconstruction of their shapes.