Fabrication of ultra-high working range strain sensor using carboxyl CNTs coated electrospun TPU assisted with dopamine

Highlights: • A strain sensor was fabricated using CNTs and modified TPU membrane. • The strain sensor possessed an ultra-high working range of 710% with a GF of 1200. • The strain sensor could accurately respond to different types of human motions. Fiber-based strain sensors have attracted widespread concern of researchers due to large specific surface area, good stretchability and remarkable flexibility. In this work, a stretchable strain sensor with ultra-high working range was developed by using electrospun thermal plastic polyurethane (TPU) nanofibrous membrane coated with carboxyl multi-walled carbon nanotubes (CNTs). In order to obtain an even distribution and an improved fastness of carboxyl CNTs on TPU fibers, dopamine (DA) was employed to modify the TPU nanofibrous membrane (labelled DATPU) via a fast ultrasonication-assisted deposition approach. DATPU/CNTs exhibited an ultra-high working range of about 710% with high gauge factor up to 1200. Furthermore, DATPU/CNTs were found to have stronger washing fastness than TPU/CNTs owing to the introduction of DA onto the surface of TPU nanofibers. DATPU/CNTs also maintained good electrical conductivity during 15,000 cycles of stretching-releasing test. Finally, a prototype of strain sensor based on DATPU/CNTs membrane demonstrated remarkable flexibility and sensitivity to human body motions such as elbow bending, finger bending and swallowing.