Extremely Stretchable, Stable, and Durable Strain Sensors Based on Double-Network Organogels

Stretchable strain sensors offer great potential for diverse applications in modern electronics. However, it is still difficult to fabricate strain sensors with extreme stretchability, high stability, and superior durability because of the challenge in elastic matrix. In this work, the first example of extremely stretchable and highly stable double-networks ethylene glycol (EG) organogel is developed for the fabrication of wearable strain sensors with high performances. It is shown that the formation of hybrid physically and chemically cross-linked double-networks endows the EG organogel with an extraordinarily stretchability as high as 21 000%, which is the highest value for gels reported in the literature. Meanwhile, the low vapor pressure of EG gives the organogel high ambient stability. Benefiting from the intrinsic stretchability and stability of EG organogel, the strain sensors are fabricated easily by incorporating graphene as electrically conductive filler, which display extremely wide strain-sensing range (>10 500% fracture strain) with a gauge factor of 2.3. More importantly, the sensor can withstand >50 000 loading-unloading cycles in air, exhibiting high stability and superior durability. It is demonstrated that these sensors can track joint movements and muscle vibrations (such as human joint motions, drinking, saying, breathing, and slight cough) of human body and even distinguish the deformations of different directions and the touches of a hair. This work not only provided a new elastic matrix platform for the fabrication of extremely stretchable, stable, and durable strain sensors but also demonstrates their applications as wearable electronic devices for tracking both large and tiny motions of human body, which could be further extended to the practical applications in electronic skin, human-machine interactions, and personalized health monitoring.