Laser‐Induced Graphene on Paper toward Efficient Fabrication of Flexible, Planar Electrodes for Electrochemical Sensing

Abstract

Laser irradiation to induce networks of graphene‐based structures toward cost‐effective, flexible device fabrication is a highly pursued area, with applications in various polymeric substrates. This work reports the application of this approach toward commonly available, eco‐friendly, low‐cost substrates, namely, chromatographic and office papers. Through an appropriate chemical treatment with sodium tetraborate as a fire‐retardant agent, photothermal conversion to porous laser‐induced graphene (LIG) on paper is achieved. Raman peaks are identified, with I2D/IG and ID/IG peak ratios of 0.616 ± 0.095 and 1.281 ± 0.173, showing the formation of multilayered graphenic material, exhibiting sheet resistances as low as 56.0 Ω sq–1. Coplanar, LIG‐based, three‐electrode systems (working, counter and reference electrodes) are produced and characterized, showing high current Faradaic oxidation and reduction peaks, translating in high electrochemical active area, doubling the geometric area. Good electron transfer kinetics performed exclusively with on‐chip measurements are reached, with k0 values as high as 7.15 × 10–4 cm s–1. Proof‐of‐concept, amperometric, enzymatic glucose biosensors are developed, exhibiting good analytical performance in physiologically relevant glucose levels, with results pointing to the applicability of paper‐based LIG toward efficient, disposable electrochemical sensor development, increasing their sustainability and accessibility, while simplifying their production and reducing their cost.

Disposable Paper-Based Biosensors: Optimizing the Electrochemical Properties of Laser-Induced Graphene

“…From our results, we found that using relatively higher fluences lead to films which can easily delaminate or become "dust like," while relatively lower powers will lead to a network of LIG that is not fully developed with some regions of amorphous carbon or even unconverted cellulose that are electrically insulating. Our findings match the parametric studies performed by other groups 21 who have reported that optimum experimental conditions yield a uniform and dense LIG network, while higher fluences can lead to ablation of the network.…”

“…Unlike the physical geometric area (0.03 cm 2 ), ECSA is the actual area of the electrode material accessible to the electrolyte for charge transfer and/or storage. The increase in the activity ratio (ratio between the ECSA and the geometric area of the electrode) can be correlated with the 3D porous fibrous and flake-like network structure of the LIG (confirmed from SEM), which provides additional accessible active sites for the electrolyte . Invariably, a higher ECSA is desirable for high-quality electrodes for electrochemical sensing .…”

“…The increase in the activity ratio (ratio between the ECSA and the geometric area of the electrode) can be correlated with the 3D porous fibrous and flake-like network structure of the LIG (confirmed from SEM), which provides additional accessible active sites for the electrolyte. 21 Invariably, a higher ECSA is desirable for high-quality electrodes for electrochemical sensing. 50 The increased ECSA and activity ratio for 1D1F electrodes thus again prove its suitability as a potent electrode material.…”

“…LIG has inherently high adhesion to the paper substrate, hence reducing the chance of delamination and improving resistance to strain, which is crucial for flexible sensors in particular. 20 Paper-derived LIG may also be combined with other highthroughput techniques such as wax printing 21 to take advantage of the fluid handling properties of paper such that the liquid analyte may be efficiently delivered and concentrated onto the sensing electrode.…”

Biocompatible Parylene-C Laser-Induced Graphene Electrodes for Microsupercapacitor Applications

“…Up to now, different native polymeric substrates have been used to produce these graphitic structures from synthetic polymers such as polyimide , or polysulfone to natural materials such as wood, cork, and paper. , For instance, Tour and his team transformed commercial polyimide films into porous graphene by simple laser induction, which was used for the fabrication of flexible, solid-state supercapacitors. Kulyk et al showed that by varying the lasing parameters, it is possible to improve the properties of LIG on paper, achieving sheet resistances of around 30 Ω/sq.…”