Enhancement of Sensing Range and Stability of Ultrasensitive Crack-Based Strain Sensor Using Atomized Liquid Metal

Biomimetic crack-based sensors are known for their ultrahigh sensitivity in strain sensing with gauge factors (GFs) of
$\sim $
2000, but the sensing range is very limited (
$\sim $
2%). We report a method of enhancing sensing range and stability of ultrasensitive crack-based sensor using atomized liquid metal droplets. A crack-based sensor was fabricated by depositing chromium (Cr)/gold (AU) (0.9/20 nm) bilayer on plasma-treated polydimethylsiloxane (PDMS) with an additional step of stretching the sensor to create myriads of cracks on metal film. After the formation of a conventional crack-based strain sensor, gallium-based liquid metal was sprayed over the sensor surface to randomly deposit atomized liquid metal droplets. Optical images of the crack-based sensor under applied strain showed that the atomized liquid metal droplets act as stretchable conductive bridges between cracks in the strain sensor. By using randomly dispersed atomized liquid metal droplets, the crack-based sensor showed higher sensitivity (
${R}/{R}_{{0}}$
of
$\sim $
238) and GF of
$\sim $
2238 compared to the crack-based sensor without liquid metal. The sensing range of the crack-based sensor was enhanced from 2.283% to 10.675% with the aid of atomized liquid metal droplets. The flexibility of the liquid metal-aided crack-based sensor was also verified through repetitive testing of stretching, bending, and twisting.