Design and fabrication of auxetic stretchable force sensor for hand rehabilitation

Using a melt electrospinning technique, stretchable force sensors were designed for use in an application of hand rehabilitation. The main purpose of this study was to verify that the use of auxetic sensors improved hand rehabilitation practices when compared to their absence. For this study, novel stretchable poly (epsilon-caprolactone) (PCL) force sensors were fabricated into the following formations: auxetic microfiber sheets (AMSs), auxetic solid sheets (ASSs), microfiber sheets (MSs), and solid sheets (SSs). A femtosecond laser device was used to make an auxetic structure in the MSs and SSs. Subsequently, these sensors were coated with gold particles to make them conductive for the electrical current resistance assays. Through the cycles of applied stress and strain, auxetic structures were able to retain their original shape once these forces have been dissipated. This stretchable sensor could potentially measure applied external loads, resistance, and strain and could also be attachable to a desired substrate. In order to verify the workability and practicality of our designed sensors, we have attempted to use the sensors on a human hand. The AMS sensor had the highest sensitivity on measuring force and resistance among the four types of sensors. To our knowledge, this is the first study to form a stretchable force sensor using a melt electrospinning technique.