A Stretchable and Strain‐Limiting, Bio‐Inspired Nanofiber‐Reinforced Microfiber for Wearable Electronics

Abstract With existing fiber‐based approaches for wearable electronics, devices with limited stretchability are not fully protected against large stretching when the wearer is participating in vigorous activities. A network of elastin and collagen fibers makes biological tissues elastic at low strains and strain‐limiting at high strains, showing a J‐shaped stress‐strain behavior. Stretchable systems can replicate a “J‐shaped stress‐strain/strain‐limiting” mechanical behavior of biological tissues under deformations and provide mechanical compliance and comfort to wearers. For mimicking this mechanical behavior of biological tissues, he developed a combined microfiber and nanofiber (NF)‐based approach. The soft polyurethane (PU) microfiber mimicking elastin of biological tissue is wrapped with stiff poly(vinylidene fluoride)(PVDF) NFs, mimicking collagen in tissue, and dip coated in polydimethylsiloxane (PDMS). Confocal images during stretching confirmed that the PU microfiber maintained stretchability, while the stiff PVDF NFs played a role in the strain‐limiting characteristics. By tailoring a loading ratio of the PVDF NFs on the PU microfiber, the elastic modulus is matched well with those of biological tissues. The stretchable conducting coating and temperature sensor on the bio‐inspired microfiber showed a negligible difference in a current‐time (I‐T) response during static and dynamic stretching which indicated the efficient absorption of stress by the bio‐inspired microfiber.