High-Performance Stretchable Strain Sensor Based on Ag Nanoparticles Sandwiched between Two 3D-Printed Polyurethane Fibrous Textiles

Developing stretchable strain sensors with high stretchability as well as sensitivity via a scalable technique is still a challenge that remains to be addressed. Herein, high-performance stretchable strain sensors based on Ag nanoparticles (NPs) sandwiched between two thermoplastic polyurethane (TPU) fibrous textiles are fabricated by combining 3D-printed TPU elastomer and solution-coated Ag NP pulp, in which a conductive network is formed at a low loading of 4.3 wt% Ag NPs. The printed TPU fibers in each textile are arranged in parallel, while perpendicular to each other between the upper and lower textiles, forming an oblique lattice structure with their diagonal being the same direction as the external force. Under stretching, the deformed TPU fibers in the upper and lower textiles squeezed Ag NPs to undergo shearing motion, such that the disconnected electrical circuit can be compensated by some Ag NPs to retain the electrical pathway. Consequently, the printed TPU/Ag strain sensors showed high sensitivity (gauge factor of 38220 at a strain of 120-138%), wide working strain range (0-138%), and long-term durability (>2500 cycles at 50% strain). Their promise as flexible electronic components is demonstrated in wearable motion detection systems for monitoring human motions and recognizing facial expressions.