Laser induced graphene (LIG) strain sensors for bending angle detection

Resumen

Due to the growing relevance of artificial intelligence, improved sensing mechanisms with a high sensitivity and response speed, reliability, and with a wide range of deformability are needed for different monitoring processes . Direct laser writing technique to produce laser induced graphene (LIG) provides an easy, accurate and economical way for obtaining graphene strain sensors with these characteristics. In view of this, in the current project, LIG strain sensors were designed and manufactured in the Institute of Optoelectronics and Microtechnology Systems (ISOM) facilities, and then were characterised electro-mechanically in the Materials Science Department of the ETSI de Caminos, Canales y Puertos (UPM). After different optimizations regarding manufacturing, LIG strain sensors transferred and encapsulated in PDMS flexible substrate were obtained, with linear response to the deformation and a gauge factor (GF) up to 100. Its durability was tested subjecting the sensor to 1500 cycles of ε = 8%, showing a response time of 2 s. The minimum resolvable distance tested was ε = 0,2 %. The applicability of manufactured sensors for bending angle detection was successfully demonstrated and a setup for knee flexion detection was proposed.