Photothermal self-healable polypyrrole-polyurethane sponge with dynamic covalent oximino bonds for flexible strain sensors

Polypyrrole-polyurethane (PPy-PU) porous materials have been widely used in the research of flexible stress/strain sensors. However, it is inevitable on material damage in the process of force sensing, and it is still a great challenge to prepare a flexible porous sensor with non-contact self-healing performance. In this study, we prepared a non-contact photothermal self-healing PPy-PU porous material containing a reversible oxime urethane bond and polypyrrole, and further packaged it into a porous sensor for strain sensing detection. The obtained PPy-PU porous material has excellent breaking elongation and breaking strength. Benefit from the excellent photothermal conversion of polypyrrole, the maximum surface temperature of the PPy-PU porous material can reach above 110 °C at 1.5-sun that is the required temperature for the cleavage and reorganization of the oxime carbamate bonds in the PU matrix, and the fracture strength of PPy-PU porous material can be restored to more than 85% after self-healing at 1.5-sun for 1 h. The most important is that the self-healing PPy-PU porous sensor can still sensitively detect strain in the range of 1%–10%. Finally, we show the application of the photothermal self-healing PPy-PU porous sensor in the field of human micro-motion, indicating its potential for human physiological monitoring and artificial intelligence.