Highly stretchable, bionic self-healing waterborne polyurethane elastic film enabled by multiple hydrogen bonds for flexible strain sensors

Abstract

Flexible elastomer materials with high stretchability and self-healing performance are the preferred substrates for preparing multi-function flexible sensors and bionic electronic skin. However, it is still a great challenge to make the material have excellent mechanical properties and bionic self-healing capability simultaneously because these two properties are contradictory. Here, a novel eco-friendly waterborne polyurethane elastomer (WPU-FM) with a six-fold hydrogen bond structure is prepared based on the molecular self-assembly design of floxuridine (DFU) and acetoguanamine (AGM) groups. The dynamic cross-linking network generated by the six-fold hydrogen bond can not only consume strain energy, but can also facilitate speedy re-formation after fracture, endowing the material with exceptional self-healing ability (healing efficiency up to ∼104.32%) and remarkable mechanical performance (tensile strength is ∼22.19 MPa and the elongation at break reaches ∼493.98%). Furthermore, a flexible conductive composite film (WPU-FM/LM) is prepared by compositing WPU-FM and liquid metal (LM) micro-droplets by a simple physical deposition method, and is further assembled into a universal flexible strain sensor. The flexible sensor has excellent sensitivity and reliability, and it can quickly and accurately monitor various types of human movement, and sense pressure. These outstanding properties make it have great potential in the fields of flexible wearable devices, human–computer interaction, bionic electronic devices, etc.