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

Abstract

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 µm), 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 µm), 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.

A Flexible Wearable Sensor Based on Laser-Induced Graphene for High-Precision Fine Motion Capture for Pilots

“…The flexible strain sensor exhibited outstanding performance, as illustrated in Table 1 . This sensor demonstrated superior sensitivity compared to the sensors utilizing alternative conductive materials and fabrication processes [ 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 ]. The sensor fabricated using four scans exhibited even higher sensitivities, reaching up to 11.5 in the range of 0.0% to 4.2%, and as high as 142.7 in the range of 4.2% to 9.0%, which is more visually represented in Figure 4 c. This indicates a more pronounced change in relative resistance compared with sensors of the first two categories.…”

Laser-induced direct graphene patterning: from formation mechanism to flexible applications

“…In 2018, Alexandre first reported that a fourfold reduction in ablation depth thickness and a doubled improvement in spatial resolution could be achieved by using a UV laser with a wavelength of 355 nm (pulse duration of 1 µs) [41] . After that, lasers with other wavelengths were widely used to prepare LIG, including 1064 nm (continuous wave) [87,88] , 532 nm (continuous wave) [82,89] , 450 nm (continuous wave) [80,90,91] , 405 nm (pulse duration of 10~50 ms) [86,92,93] , 355 nm (pulse duration of 10 ps) [83] , 343 nm (pulse duration of 220 fs) [94,95] , and 308 nm (pulse duration of 20 ns) [96] , indicating that the preparation of LIG is independent of laser sources. Compared to laser sources with long pulse widths (continuous wave, millisecond, microsecond, and nanosecond), ultrafast lasers (pulse duration of picosecond and femtosecond) enable higher processing resolution due to the smaller heat-affected zone.…”

Laser-Guided, Self-Confined Graphitization for High-Conductivity Embedded Electronics

“…Existing LIG processing techniques primarily focus on surface irradiation, thereby requiring additional encapsulation procedures after LIG fabrication. Unfortunately, this process often causes damage to the LIG due to its inherently porous and delicate features [ 25 ]. More importantly, this surface lasing process leads to the inevitable exfoliation and oxidation of the as-formed graphene, negatively impacting the integrity and electrical property of LIG [ 26 , 27 ].…”