Wearable Flexible Strain Sensor Based on Three-Dimensional Wavy Laser-Induced Graphene and Silicone Rubber

Abstract

Laser-induced graphene (LIG) has the advantages of one-step fabrication, prominent mechanical performance, as well as high conductivity; it acts as the ideal material to fabricate flexible strain sensors. In this study, a wearable flexible strain sensor consisting of three-dimensional (3D) wavy LIG and silicone rubber was reported. With a laser to scan on a polyimide film, 3D wavy LIG could be synthesized on the wavy surface of a mold. The wavy-LIG strain sensor was developed by transferring LIG to silicone rubber substrate and then packaging. For stress concentration, the ultimate strain primarily took place in the troughs of wavy LIG, resulting in higher sensitivity and less damage to LIG during stretching. As a result, the wavy-LIG strain sensor achieved high sensitivity (gauge factor was 37.8 in a range from 0% to 31.8%, better than the planar-LIG sensor), low hysteresis (1.39%) and wide working range (from 0% to 47.7%). The wavy-LIG strain sensor had a stable and rapid dynamic response; its reversibility and repeatability were demonstrated. After 5000 cycles, the signal peak varied by only 2.32%, demonstrating the long-term durability. Besides, its applications in detecting facial skin expansion, muscle movement, and joint movement, were discussed. It is considered a simple, efficient, and low-cost method to fabricate a flexible strain sensor with high sensitivity and structural robustness. Furthermore, the wavy-LIG strain senor can be developed into wearable sensing devices for virtual/augmented reality or electronic skin.

Materials, Electrical Performance, Mechanisms, Applications, and Manufacturing Approaches for Flexible Strain Sensors

“…For example, highly sensitive flexible motion sensors consisting of gallium nitride piezoelectric nanogenerators and light emitting diodes were fabricated utilizing the laser lift-off process, [ 241 ] which exhibits good recognizability for bending and strain motions. To investigate the mechanism and technologic characteristics of laser lift-off process of polyimide film, Huang et al presented a flexible strain sensor on ultrathin PI film (2 μm) after being released from the glass substrate without any damage and wrinkle [ 242 ]. Additionally, this study provides an attractive route to optimize the laser lift-off process for large-scale production of ultra-thin flexible electronics.…”

Silicone Rubber Composites Reinforced by Carbon Nanofillers and Their Hybrids for Various Applications: A Review

“…Recently, flexible strain sensors based on polymer or rubber composites have been favorable for the above applications. These strain sensors based on polymer composites offer various advantages, such as high flexibility [ 8 ], robust stretchability [ 9 ], high gauge factor [ 3 ], and high sensitivity [ 10 ]. Promising strain sensors probably exhibit a high sensitivity to compressive or tensile strain originating from various mechanical motions [ 7 ].…”

Stretchable MXene/Thermoplastic Polyurethanes based Strain Sensor Fabricated Using a Combined Electrospinning and Electrostatic Spray Deposition Technique

“…It is widely used for health monitoring and motion detection [ 1 , 2 , 3 , 4 , 5 ]. However, most of the reported strain sensors are not capable of achieving both high sensitivity and broad sensing range, limiting their application [ 6 , 7 , 8 , 9 , 10 ]. Strain sensors based on one-dimensional conductive materials can obtain a larger stretch range, but the sensitivity is reduced.…”