Crack-Based Strain Sensor with Serpentine Structure for Real-Time Motion Monitoring in Electronic Skin Applications

Stretchable strain sensors play a pivotal role in emerging applications such as electronic skin and soft robotics, where the accurate monitoring of mechanical deformation is essential. The performance of these sensors is primarily determined by two key parameters: sensitivity and the sensing range. However, these parameters often exhibit a trade-off relationship, where enhanced sensitivity compromises the sensing range, and vice versa. In this study, we present a highly stretchable and conformal strain sensor that overcomes this limitation by integrating crack-based sensing mechanisms with a serpentine structural design. The sensor is fabricated using a simple and reproducible semiconductor-based process, comprising a gold (Au) layer thermally deposited onto a styrene-ethylene-butylene-styrene block copolymer substrate. By precise control of the deposition rate and Au film thickness, crack initiation and propagation are regulated to maximize sensitivity. The serpentine architecture not only extends the sensing range by enhancing stretchability but also ensures a uniform stress distribution across the sensor surface. The resulting device demonstrates an exceptionally high gauge factor of 321.63, a strain detection range exceeding 200%, and consistent performance over 1000 loading–unloading cycles. Furthermore, the sensor effectively detects both minute physiological signals─such as facial muscle movement and vocal cord vibration─and significant mechanical deformations, including joint articulation and plantar pressure. These results highlight the potential of the proposed sensor for applications in soft robotics, wearable electronics, and human–machine interfaces.