A Magnetically Self‐Aligning, Fast Full‐Device Self‐Healing, Skin‐Attachable Liquid Metal Strain Sensor Based on Photothermal Polyurethane

Abstract There is a growing need for research on self‐healing materials capable of spontaneously repairing physical damage, allowing the fabrication of highly durable wearable devices featuring flexibility and stretchability. Herein, the study reports on the fabrication of a novel, magnetically aligning, fully and rapidly self‐healing skin‐attachable biosensor based on newly synthesized photothermally self‐healing polyurethane. By introducing photothermal amine‐capped aniline trimers to selectively self‐healable polyurethane, the synthesized self‐healing polymer achieves a fast and high recovery rate of 81.1% from complete bisection upon laser irradiation for just 3 min. Additionally, a thin‐film type strain sensor fabricated via the spray patterning of liquid metal EGaIn as an electrode onto the surface of the self‐healing polymer exhibits a high sensitivity to strain from deformation, enabling the real‐time monitoring of bio‐signals. Furthermore, the integration of a magnetic aligning layer directly patterned and embedded onto the self‐healing polymer enhances the self‐healing performance of the sensor after damage by 4.3 times on average, compared to when using manual alignment. In short, this work demonstrates a high‐performance fully self‐healing electronic device via the synthesis of novel fast self‐healing photothermal polymers and the introduction of patterned liquid metal electrodes and magnetic alignment layers.