High-Sensitivity Flexible Strain Sensor with the Inverted Pyramid Microstructure Array Based on Stress-Induced Regular Linear Cracks

Crack-based flexible strain sensors inspired by a spider’s slit organs have exhibited high sensitivity. However, the sensitivity of crack-based sensors can be negatively affected by cracks with random and undirected features. In this work, we fabricated a high-sensitivity flexible strain sensor with regular linear microcracks induced by stress concentration. The sensor consists of a polydimethylsiloxane (PDMS) flexible substrate with an inverted pyramid array and a conductive metal layer of Ti/Au film that was sputtered on the substrate surface. When the sensor was stretched, stress concentrations will occur near the inverted pyramids, inducing the generation of linear microcracks perpendicular to the stretching directions between the adjacent inverted pyramids. The testing results demonstrated that the sensor has a high sensitivity (a gauge factor of 9327 in the strain range of 7.6–10%), a wide working range (0–10% strain), and a fast response/recovery time (77/82 ms). These features enable the sensor to have potential applications in health monitoring and human–computer interaction, such as finger motion recognition and neck bending direction detection.