Application of Coke-Based Graphene Produced via Ultrasonic Ball Milling in Flexible Strain Sensors

Graphene has exceptional electrical and mechanical properties, which make it an ideal material for wearable flexible strain sensors. However, its efficient and eco-friendly production remains constrained by challenges such as a complex process, high cost, and environmental pollution. To address those issues, this study proposes an ultrasonic ball milling method in a NMP bath using NMP as a solvent, incorporating alumina abrasive as microballs and stearic acid as interlayer additives to exfoliate coke into coke-based graphene. The resultant coke-based graphene is employed in the fabrication of sandwich-type flexible strain sensors. Tests indicate that the sensor exhibits excellent tensile strain (0–20%) and pressure strain (0–1000 kPa) sensing performances, maintaining stable operation after 500 tensile tests and 500 pressure tests, with quick response times (tensile strain response time: 257/353 ms, pressure strain response time: 192/256 ms). When applied to the human body, it can monitor the relative changes in resistance due to movement and the stimulus signals caused by external factors on the skin's surface. This method holds significant application value for the eco-friendly and low cost preparation of graphene, enabling high-quality and large-scale production of graphene strain flexible sensors.