Strain Amplification via Helically Braided Fiber Reinforced Sleeve for Soft Material Energy Harvesting

Abstract Soft, elastic materials (e.g., elastomers and gels) are useful for emerging devices that can deform, such as stretchable electronics and soft robots. Mechanisms exist to sense such strain deformation or convert it into electricity. This study proposes a way to amplify (increase) the strain applied to soft materials for a given external strain and thereby make more effective sensors and energy harvesters. The approach relies on a helically braided fiber reinforced sleeve that serves two purposes: 1) it adds strength and mechanical reinforcement to the soft materials it encases, while maintaining compliance and softness, and 2) it squeezes the soft material during strain, thereby elongating it and increasing the “effective” strain. As a demonstration platform, we focus on its utility for soft and stretchable variable‐area electrical double layer (EDL) supercapacitor energy harvesters made of hydrogel with liquid metal electrodes. Kinematic modeling of the braided sleeve quantifies the relationship between sleeve geometry parameters and effective strain. Simulations and experiments with fabricated EDL supercapacitor energy harvesters confirm increases in peak current due to the braided sleeve. These findings suggest a simple route to enhance the sensitivity of strain sensors and the performance of mechanical energy harvesters in devices built from soft materials.