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Laser-scribed graphene (LSG) electrodes have gained popularity in many miniaturized and lab on chip systems such as micro-energy harvester, flexible electronics, portable power storage, electrochemical sensors, etc. This study presents the development of a fuel cell on a cellulose filter paper with integrated LSG electrodes. Here, cellulose paper acts as a microchannel to transport the fluids through capillary action. Paper devices offer several important advantages, including the elimination of membrane and external pumps with the integrated co-laminar flow through embedded capillary systems. Herein, the paper-LSG fuel cell uses HCOOH and H2SO4 as fuel and electrolyte, respectively. Experiments have been performed to enhance the performance of paper-LSG fuel cell by optimizing various electrode types (Plain LSG, Multi-walled carbon nanotubes (MWCNT)/LSG, Pure MWCNT), concentration of fuel and electrolyte, and different grades of cellulose paper microchannels to understand the impact to the porosity of paper. The developed paper-LSG fuel cell, with MWCNT/LSG as an optimized electrode, delivered a peak current density (CD) of 166.82 µA/cm2, and power density (PD) of 14.42 µW/cm2, at a stable OCP of 350 mV with Grade-1 cellulose microchannel. Such fuel cells are amenable to be utilized for sustainably powering various microelectronic devices. [ABSTRACT FROM AUTHOR]

Membraneless Microfluidic Paper Fuel Cells (MMPFCs) are promising devices to harvest energy for various portable applications. This is primarily because such devices eliminate the need for membrane, and external pumps due to the built-in co-laminar flow, and embedded capillaries, respectively. However, these devices have enormous scope to optimize their performance. Herein, investigations on MMPFC have been carried out with varying electrode separation, whereby cellulose papers acts as the microchannel of MMPFC. Here, various grades of carbon-supported graphite pencils serve as electrodes, formic acid acts as a fuel, and sulphuric acid works as an electrolyte. Oxygen from the atmospheric air acts as an oxidant for ionic exchange under co-laminar flow in the MMPFC. These MMPFCs with the optimized configuration provide enhanced energy densities with different grades of the microchannel material along with variation in electrode separation. Leveraging grade 1 Whatman cellulose paper as MMPFC microchannel with 1 mm electrode separation, the MMPFC generates energy with a maximum open-circuit potential of 0.49 V, a maximum current density of 2.45 mAcm−2 and power density of 0.26 mWcm−2. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]