Microchannel-Confined Chinese Ink-Based Highly Stretchable Liquid-State Strain Sensor for Early Warning of Road Collapse

Stretchable strain sensors are widely used in the fields of wearable devices, soft robotics, healthcare monitoring, and more. Despite tremendous efforts, strain sensors capable of detecting large-scale soil deformation for urban geological hazard prevention have not yet been demonstrated. In this paper, a soft strain sensor of a highly stretchable Ecoflex-0030 elastomeric matrix with microchannel-confined environmentally benign conductive Chinese ink as the liquid-state strain-sensitive material that can reliably detect a wide range of working strain up to 300% is demonstrated. The sensor exhibits a negligible hysteresis error of 2.1%, with a considerably good gauge factor of 1.95. The sensor performance is evaluated under both creep and cyclic loading tests, indicating superior stability (0.65% fluctuation), and repeatability (0.28% variation in 1000 cycles), even under a lower underground environment temperature of 18 degrees C. As a proof-of-concept demonstration, a liquid-state strain sensor array with a strain amplification mechanism capable of accurately monitoring the formation of various underground cavities and providing timely demanded information for early warning of catastrophic road collapse is demonstrated and verified by the computer vision-based particle image velocimetry (PIV) method. A highly-stretchable liquid-state soft strain sensor array is presented for early warning of catastrophic road collapse, enabling real-time structure health monitoring (SHM) in underground space. Equipped with the Chinese ink, the sensor exhibits excellent properties such as superior stability, low hysteresis error, low temperature adaptability, and high repeatability.image