Laser-Induced Graphene on Polyimide: Material Characterization Toward Strain-Sensing Applications

Abstract

Highlights: What are the main findings? Low-power laser scribing of polyimide produced porous graphene-like conductive patterns suitable for strain sensing. Laser power was the most critical parameter, yielding sheet resistances down to ~20 Ω sq−1 and a gauge factor up to ~1.1. Increasing the number of laser passes (multiple engravings) deteriorated graphene material quality and significantly reduced the strain gauge factor of the sensor. What is the implication of the main finding? A 450 nm diode laser can be used to fabricate low-cost, flexible graphene strain sensors without chemical processes. This approach enables accessible production of strain gauges on polymer substrates for flexible electronics and structural health monitoring. The feasibility demonstrated here suggests that inexpensive diode lasers could be deployed for on-demand graphene-based sensor fabrication, potentially accelerating research and applications in wearable and flexible sensor technology. This study investigates the effect of laser power, focal length, and number of passes on the fabrication of graphene-based strain sensors using a 450 nm diode laser at the upper limit of the UV spectrum. Polyimide substrates were irradiated to produce laser-induced graphene, and the resulting sensors were evaluated under three-point bending tests. The main requirements for deformation sensors—adequate conductivity, mechanical stability under bending, and high sensitivity (gauge factor)—were assessed through morphological analysis by SEM, Raman spectroscopy, and electrical characterization using the Van der Pauw method. The results indicate that laser power is the critical factor influencing graphene quality and sensor performance, while focal length has a negligible effect and additional passes reduce material quality and sensitivity. Overall, this work demonstrates the feasibility of producing functional, low-cost graphene strain sensors with a commercial diode laser, offering a scalable and affordable alternative for sensor fabrication.