Ultra-stretchable, tough, and self-healing polyurethane with tunable microphase separation for flexible wearable electronics

Abstract

The development of flexible wearable materials that combine high toughness, stretchability, and compatibility with the modulus of human skin remains a significant challenge, due to inherent trade-offs between strength and elongation. These materials must demonstrate mechanical durability and resistance to environmental factors such as moisture and sweat. Herein, we present a polyurethane elastomer (HTPB-PU) that is ultra-stretchable, tough, thermodynamically stable, self-healing, biocompatible, and transparent, specifically designed for flexible wearable electronics. The elastomer incorporates a hydrophobic soft segment and varying concentrations of disulfide bonds to enable tunable microphase separation. This approach leads to the uniform distribution of hard-phase aggregates, resulting in exceptional properties, including a tensile elongation of 2180 %, a toughness of 42.8 MJ m⁻³, and a Young’s modulus of 110 kPa, allowing it to support objects weighing 16,666 times its own weight below it. Additionally, the material exhibits self-healing at 36 °C and retains stability over 300 cycles at 150 % strain, even after 30 days of immersion in water and synthetic perspiration. Moreover, a stretch sensor capable of detecting physiological signals, including pulse and throat vibrations, was developed by integrating the material with liquid metal, demonstrating its potential for health monitoring and intelligent wearables.