Construction of laser-induced graphene/silver nanowire composite structures for low-strain, high-sensitivity flexible wearable strain sensors

Sandwich-structured flexible sensors based on graphene have high sensitivity and stability. When graphene is combined with a flexible substrate in a sandwich structure, the weak bonding between them compromises the sensor's stability and sensitivity at low strains. This presents challenges in monitoring subtle physiological activities, such as hand bending and pulse rate. For this purpose, laser-induced graphene (LIG) is proposed to be used to prepare flexible sensors in order to improve the sensitivity and stability of the sensors at low strains. Polydimethylsiloxane (PDMS) with low modulus and polyimide (PI) with rich carbon content are selected as precursor materials for LIG, and graphene is formed through laser induction. Subsequently, silver nanowires (Ag NWs) solution is added to LIG to give the sensor low strain and high sensitivity performance. When the PI/PDMS ratio is 1:3, the Ag NWs/LIG flexible strain sensor exhibits excellent sensitivity (GF=778.468) over a small strain range (8.76%-11.25%). Meanwhile, the sensor still shows excellent stability after 2000 cycle experiments. The Ag NWs/LIG flexible strain sensor shows good performance when placed on the back of the hand, around the eyes, etc. It is demonstrated that Ag NWs/LIG flexible strain sensors have good application potential in human physiological activity monitoring, health management and medical fields, and provide a low-strain, high-sensitivity sensor design strategy for flexible wearable devices.