Direct ink writing of a graphene/CNT/silicone composite strain sensor with a near-zero temperature coefficient of resistance

The development of wearable strain sensors with a zero temperature coefficient of resistance (TCR), which is crucial to overcome the problem of temperature disturbance, has been scarcely studied. Herein, highly stretchable graphene nanoplatelet (GNP)/carbon nanotube (CNT)/silicone elastomer (GCE) fibers are successfully prepared via a facile direct ink writing technique. The GCE fibers fabricated consist of CNTs and GNPs having a negative temperature coefficient (NTC) and a positive temperature coefficient (PTC), respectively. As a result, the obtained GCE fiber by adjusting the mass ratio of CNTs and GNPs shows a near-zero TCR (1.14 x 10(-4) degrees C), which is the lowest one compared with the reported values in the literature. Besides, the GCE strain sensor exhibits the highest sensitivity (gauge factor (GF) = 14550.2 for 100% strain) compared with the data reported previously, and a wide working range (1 to 100%), a low detecting limit (1% strain), a quick response time (170 ms) and a high durability (after 10 000 loops). In addition, the GCE strain sensor shows an excellent electrical stability under external conditions including longstanding storage and humidity/water exposure. Finally, various human movements are detected under water and high temperature conditions to demonstrate the outstanding sensing performance and response stability of the GCE strain sensor.