Efficient fabrication of highly stretchable and ultrasensitive thermoplastic polyurethane/carbon nanotube foam with anisotropic pore structures for human motion monitoring

Conductive elastic polymers have become one of the most promising flexible sensor materials because of their superior mechanical and electrical properties. However, the contradiction between the wide detection range and high sensitivity of a strain sensor based conductive elastic polymer limits their development in wearable electronic devices. Herein, an effective morphology control method that combines melt blending and chemical etching is proposed for fabricating highly stretchable and ultrasensitive thermoplastic polyurethane (TPU)/carbon nanotube (CNT) strain sensors with anisotropic pore structures. A porous TPU/CNT strain sensor is formed when stretched polylactide (PLA) is etched as a sacrificial template and the CNTs are uniformly dispersed in the TPU foam to construct homogeneous three-dimensional conductive networks. As expected, the as-prepared porous TPU/CNT strain sensor with 3 wt% CNTs exhibits a wide detection range of 221% and an ultrahigh sensitivity of 1189.19 because anisotropic TPU porous structures intensify the destruction of dense CNT conductive networks. And the porous TPU/CNT strain sensor has a low detection limit of 1% and excellent response stability and durability. Consequently, the porous TPU/CNT strain sensor can be utilized as an electronic skin to monitor human motion, including large movements of joints and subtle movements of the face. The proposed method for the efficient fabrication of a conductive elastic polymer offers a new chance for the development of excellent flexible sensor materials. The highly stretchable and ultrasensitive TPU/CNTs porous sensors with anisotropic pores have been fabricated efficiently for human motion monitoring.