Automated pencil electrode formation platform to realize uniform and reproducible graphite electrodes on paper for microfluidic fuel cells

Abstract

Graphite pencil stroked electrodes for paper-based Microfluidic devices are gaining immense attention due to their electrochemical properties, cost efficiency, and ease-of-use. However, their widespread use has been hindered by the challenges associated with their manual fabrication such as non-uniformity in graphite deposition, applied pressure, etc. This work presents the design and development of an automated graphite pencil stroking device for graphite electrode fabrication with high efficiency through a compact, inexpensive and automatic process, with reduced fabrication time and human intervention leading to more uniformity. The motion platform of Graphtec plotter was used to create multiple strokes with the help of the proposed device. Such inexpensive graphite electrodes (less than the US $1) have been observed to be porous in nature, acting as diffusion agents. The automated graphite electrodes were used to study the performance of microfluidic paper fuel cells (MPFCs) with formic acid, oxygen, and sulphuric acid acting as fuel, oxidising agent and electrolyte respectively. From this configuration, the maximum current density and power density were measured to be 1,305.5 µA cm −2 and 135.5 µW cm −2 , respectively at 0.3 V stable OCP at 100 strokes. Overall, the study enumerates the development of an automated pencil stroke device for fabricating graphite electrodes, which can potentially be harnessed in numerous miniaturized paper based applications. Microfluidic devices with integrated electrodes, or electromicrofluidic devices, have attained essential roles in diverse areas, including energy harvesting for portable applications and sensing devices 1-3. Paper-pencil based microfluidic fuel cell is one of the most recent vital advancements to develop point of the source (POS) and point of care (POC) devices owing to the well-proven benefits of microfluidic environment and graphite electrodes 4,5. In recent years, graphite pencils are being used as electrodes and have shown encouraging outcomes and promising features of MPFCs when compared with the existing approaches. Initially approaches on graphite electrodes, Aoki et al. demonstrated the first use for of graphite material (pencil lead), as electrodes 6. Bandapati et al. investigated the performance of membraneless glucose biofuel cell with various grades of graphite pencils act as electrodes 7,8. Rewatkar et al. examined 3D printed enzymatic biofuel cell performance with graphite pencil as an electrodes 9. In spite of the numerable benefits of such devices, they come with an inherent setback of the physically fabricated electrodes with non-uniform deposition of graphite due to the subjective nature of the applied pressure and manual counting of the number of strokes. Most of the recent researches in the field of paper-pencil based microfuel cells employ manual deposition of graphite on the paper for fabricating the electrode. Arun et al. reported formic acid microfluidic fuel cell with manual graphite pencil electrodes with diverse grades of pencils 1...

Advances in microfluidic electrochemical fuel cells in recent years

“…10). 91 Adam S. Hollinger et al . proposed an electrohydrodynamic‐jet (e‐jet) printing method which can deposit many types of materials onto the electrodes and ensure uniform distribution 92 .…”

“…(open access figure distributed under the terms of the Creative Commons CC BY license. ) 91 (2) Simulation model used to research the performance of a MFEFC powered by vapor. Reprinted with permission from Wang et al .…”

Additively Manufactured Microfluidic Enzymatic Biofuel Cell with Comb -like Bioelectrodes

“…The study was conducted using a three-electrode system wherein the electrolytes were prepared in 0.1 M PBS at room temperature conditions. Initially, the substrate concentration was optimized for the bioanode, which is a critical factor(Tata Rao et al 2020). This was done by using the electrochemical technique, LSV at a maximum potential of 0.4 V in a range of glucose concentrations from 20-80 mM.…”

“…The complete micro uidic device with integrated 8 comb-like structured bioelectrode was fueled with glucose (60 mM) and PBS (0.1M, pH 5) with a ow rate of 18 ml/hour. Polarization curves were plotted using current density and applied voltage (Rao et al 2020). From gure 5d, it can be interpreted that, at higher current densities, the ohmic loss is minimum, whereas activation loss in the system is high.…”

Development of Membraneless Paper‐pencil Microfluidic Hydrazine Fuel Cell

“…From literature, the mass percentage of graphite (68 % in HB, 90 % in 8B), wax, and clay in various grades of pencils are known, suggesting that the pencils with more graphite content have lesser resistance and vice versa (Table S2). In addition, the resistance of the 8B electrode was reported to be much lower than that of the HB electrode [27]. Owing to this fact, the higher resistance electrode (HB) was used as an anode, while the lower resistance electrode (8B) was used as a cathode on the fuel cell platform.…”