A flexible sensor fabricated by laser-induced graphene on PI fabric with macroscopic crack array for GF modulation strategy

In numerous fields such as digital health, soft robotics, and artificial intelligence, there is a growing demand for sensing various types of weak signals. In response to this need, flexible sensors should possess characteristics such as high sensitivity (i.e., gauge factor, GF), good conformability and high cyclic stability. So, in this study a simple method was employed to prepare flexible sensors using a polyimide (PI) fabric as a flexible substrate and hot-press molding technique. Furthermore, a strategy was proposed to adjust the GF using a macroscopic crack array. Compared to traditional film substrates, fabric substrates exhibit better conformability and can be designed into variable curvature structures, presenting greater potential for various applications. Experimental data illustrate that the designed flexible fabric sensor exhibits exceptional linearity within the 0–10% strain range, with a linearity value of 0.99747. Subsequently, an extremely simple and cheap strategy for modulating the GF was proposed based on such fabric structure. The strategy is engraving an array of cracks on the surface of the sensor. The GF of the crack arrays sensors was boosted to 25 times of that without engraved crack arrays. The sensors with and without crack arrays finally accomplished the sensing tests of finger bending signal, breathing signal, blinking signal, and speech signal successfully. Therefore, the proposed sensor preparation scheme and GF enhancement strategy in this study exhibit strong potential for applications in the field of wearable flexible electronics.