Finite element analysis of stress distribution in soft sensors under torsional loading

The wearable and flexible sensors are enabling advances in next-generation technologies such as soft robotics, mobile healthcare, internet of things etc. In consequence, novel materials and manufacturing methods have received most of the attention so far. However, with the growing use of these technologies in real applications, other important areas such as mechanical reliability under repeated mechanical deformations also require greater consideration. A few studies covering this aspect have mainly focused on mechanical stress under simple bending conditions and ignored stress evolution under twisting (torsional) movements. The present work studies the influence of different parameters such as carrier substrate dimensions and its material and twisting angles on the stress distribution during torsional movements using finite element method. Following this, highly stretchable strain sensors are fabricated using nanocomposite of carbon nanotubes and Ecoflex™ and tested under various twisting angles. The soft strain sensor possesses excellent repeatable and robust torsional strain detection properties with >100% change in resistance at ±90° of twisting and has shown potential for wearable and robotics applications.