Laser-induced graphene based on the controllable angle between two irradiation steps for the fabrication of flexible sensor

Abstract

Graphene, a carbon material with high carrier mobility and low current density, is a promising candidate for the fabrication of flexible sensors. However, its production using traditional methods is complex and expensive, whereas the synthesis of laser-induced graphene (LIG) is eco-friendly and inexpensive under ambient conditions. LIG features a 3D porous structure with localized defects, which is influenced by substrate properties, laser parameters, and processing steps. Herein, the influence of the twist angle between two laser irradiation steps on the porous structure and conductive characteristics of LIG is explored. The results show that the optimal twist angle is 4°, at which the square resistance of LIG is as low as 12.0 Ω sq⁻¹. The change in the conductivity of LIG occurs because the optimal twist angle between the two graphene layers opens the band gap. LIG with a twist angle of 4° is selected to prepare a biosensor and a Hall sensor. It is found that the LIG-based biosensor exhibits a lower detection limit of 8.62 μM when detecting uric acid (UA). Furthermore, the Hall sensitivity of the cross and circular Hall sensors is ∼0.59 and ∼0.64 V (A⁻¹ T⁻¹), respectively. This study supports the application of LIG in flexible sensors and provides some guidelines for further exploration of the 3D structure of LIG.