A pressure-redistributing insole using soft sensors and actuators

Soft robotics has garnered great research interest from robotics community due to their compliant control as compared to normal hard rigid robots. Particularly, these soft actuators only involve simple design of pneumatic channels to generate required actuation and are usually powered by pneumatics or hydraulics. These actuators are usually lightweight, inexpensive and easily fabricated with soft lithography technique. In this paper, we present a different application of soft robotics in shoe insole design that involves simple design and control. To our knowledge, this is the first study to design soft sensors and actuators which aim to redistribute the plantar pressure and eventually tackle foot problems such as ulcers and blisters. The abnormal, high repetitive stresses acting on the foot tissues can cause immediate breakdown of foot tissues, which will lead to ulcers and even a serious pathology that require foot amputation. A mold with a peripheral pneumatic ring channel feature was designed using computer-aided drawing and thereafter 3D-printed. Subsequently, elastomeric material was poured into the mold and cured to create a negative replica of the mold, which is then sealed using another 2mm layer of elastomeric material. Upon pressurization, the pneumatic channel embedded in the actuator will inflate in the regions that are most compliant and cushion the plantar soft tissues as well as reduce the peak plantar pressure.