Laser-Induced Graphene Electrodes on Poly(ether–ether–ketone)/PDMS Composite Films for Flexible Strain and Humidity Sensors

Laser-induced graphene prepared on polymer substrates with a high modulus is a widely applied method to fabricate varied flexible electronics; however, the resulting relatively poor stretchability considerably limits its applicability. In this paper, an elastic composite consisting of poly(ether–ether–ketone) powder and poly(dimethylsiloxane) (PDMS) is reported to fabricate stretchable electrodes using direct laser-induced graphitization without transferring. The liquid composites before curing can be cast into various shapes for different applications. To balance the conductivity and stretchability of stretchable electrodes, we optimized the composite mass ratios and laser parameters and performed a series of morphological and performance characterizations on the composites; furthermore, we analyzed the elemental composition and functional groups of the laser-induced products. With the proper encapsulating method, strain sensors were prepared, exhibiting high sensitivity (a gauge factor of 78) and a stable resistance response over 50% operating range with the ability to monitor both fine pulse beats and larger strains such as human joint movement. Furthermore, a humidity sensor composited with laser-patterned interdigital electrode and graphene oxide on the elastic composite substrate had characteristics of high sensitivity (14.18 pF/%RH) and fast recovery time (9 s), which could be used for breathing monitoring and noncontact sensing. In conclusion, laser-induced graphene prepared in one step on a stretchable composite film of polymers with a high modulus and low modulus is a promising method to fabricate wearable electronics.