Tough, Stretchable and Fast Self-Healing Polymer Based Highly Sensitive Pressure Sensor

There have been extensive studies on self-healing materials and devices for extending the lifespan of soft electronic devices. In particular, the research on self-healing by specific stimulus such as heat, light, or moisture is in active progress.<br/>In this work, we report on newly synthesized tough, stretchable, and fast self-healing polymer and its application to highly sensitive self-healing pressure sensor. Our thermo-responsive self-healing polymer based on oxime-carbamate bonds and disulfide bonds is synthesized via condensation polymerization of poly(tetramethylene glycol) as soft segment, isoporone diisocyanate as hard segment, dimethyl glyoxime and aminophenyl disulfide as chain extender, and 1,4-butanediol diglycidyl ether as crosslinker. The synthesized polymer exhibits the toughness of 8.1 MPa and stretchability of 1003.6 %. The toughness of the polymer is enhanced by introducing an epoxide group as a crosslinker Oxime-carbamate bonds and disulfide bonds broken by physical damages including complete bisection can be dynamically regenerated by heating at 65 °C for 1 hr, resulting in high self-healing efficiency of 85.1 %. Self-healing properties remained even in water with varying pH levels from 1 to 10 at room temperature for 1 hr. Based on this tough and self-healing polymer, a highly sensitive pressure sensor is fabricated with a mechanical stability over 1000 repetitive cycles of pressing/releasing. Incorporation of micro pyramid structure and interdigitated Au electrodes enhances the sensitivity up-to 150 kPa^-1 in the range of 0-1 kPa. With the fabricated sensor attached onto human skin, various bio-signals are detected Furthermore, the fabricated pressure sensor is fully self-healing from complete bisection, recovering the pristine. This work demonstrates the high potential application of our novel synthesized tough, stretchable, and fast self-healing polymer to soft skin-attachable devices with longevity.