Highly Sensitive, Ultrastretchable Strain Sensors Prepared by Pumping Hybrid Fillers of Carbon Nanotubes/Cellulose Nanocrystal into Electrospun Polyurethane Membranes

Advanced flexible strain sensors for human motion detection and other potential use have attracted great attention in recent years. However, the preparation of strain sensor with both high sensitivity and large workable strain range remains a challenge. In this work, the carbon nanotube (CNT) suspensions with the assistance of cellulose nanocrystals (CNC) were directly pumped into the porous electrospun thermoplastic polyurethanes (TPU) membranes through a simple filtration process to prepare the flexible strain sensors in one step. The sensitivity and workable strain range of the strain sensors are tunable by changing the mass ratios of CNTs/CNC and the total amount of hybrid fillers. With increase in the total amount of fillers, a change of filler layer from droplet to completely continuous film was observed, resulting in a sharp increase of strain sensitivity. By combining the ultraelasticity of the TPU material and the high sensitivity of hybrid fillers, the strain sensor with large workable strain range (>500%) and high sensitivity (gauge factor = 321) was successfully prepared. Its applications in visual control and full-range human body motion detection were demonstrated, showing its tremendous potential applications in future intelligent electronics.