Ultrathin, Graphene-in-Polyimide Strain Sensor via Laser-Induced Interfacial Ablation of Polyimide

Laser-induced graphene sensors have attracted considerable interest in various fields; however, the low sensitivity and conformability limit their further applications in measuring soft, large deformable structures. Here, an innovative method of interface ablation is presented to convert the interfacial polyimide into graphene by nanosecond ultraviolet laser (308 nm). Significantly different from the traditional laser surface ablation, interface ablation demonstrates its unique capacity to produce high-quality graphene with limited ablation depth, which benefits from the combined effect of highly concentrated temperature distribution, the confinement of reaction product, and a unique ablation mode dominated by heat conduction. Using this method, an ultrathin (8 mu m), graphene-in-polyimide (GiP) strain sensor is obtained, which is six times thinner than that prepared by the traditional surface ablation. The ultrathin GiP sensors exhibit excellent conformability (small bending radius of 400 mu m), high strain sensitivity (24.8), and high force sensitivity (4.2 N-1). Demonstrations of this GiP strain sensor in the deformation measurement of the morphing aircraft (e.g., bending, twisting, and impact) illustrate its powerful abilities in the health monitoring of equipment, thus providing engineering opportunities for smart devices requiring accurate deformation measurement.