Shellac-mediated laser-induced reduced graphene oxide film on paper and fabric: exceptional performance in flexible fuel cell, supercapacitor and electrocardiography applications

Abstract

The versatile properties of graphene and ancillary materials in various areas have accelerated the development of optimized methods, particularly using natural sources. Herein, natural shellac (biopolymer) (C₂₅H₅₁COOH), with inherent long carbon chains, is leveraged as a potential resource in improving the physiochemical properties of laser-induced reduced graphene oxide (rGO). A versatile 450 nm blue diode laser produced biopolymer-assisted rGO on environmentally friendly flexible paper and cloth samples. The methodology led to the formation of improved rGO with electrical sheet resistances as low as 2.3 Ω Sq.⁻¹ Moreover, thorough characterizations revealed that the average number of rGO layers is as low as 11. The potential of shellac-assisted rGO was validated in four significant applications. First, a disposable 2-electrode enzymatic biofuel cell (EBFC) was developed on biopolymer-assisted paper samples, which led to the generation of a power density of 66.7 μW cm⁻². Second, rGO interdigitated electrode (IDE) supercapacitors were patterned over dual shellac varieties of paper and showed a maximum areal capacitance of 31.25 mF cm⁻² at a current density of 0.5 mA cm⁻². Third, the rGO-patterned electrode system on biopolymer-assisted paper successfully yielded notable conventional ECG signals, specifically P, R, T, and QRS complexes. Moreover, the signal-to-noise ratio (S/N ratio) notably increased to 24%, surpassing the S/N ratio observed using the conventional Ag/AgCl electrode system. Ultimately, printed electronic circuits were demonstrated on cloth samples for wearable applications. The utilization of natural biopolymers to enhance rGO holds significant promise for a wide range of potential applications in the future.