Performance optimization of microfluidic paper fuel‐cell with varying cellulose fiber papers as absorbent pad

Abstract

Summary Miniaturization of devices, combined with other features such as portability, proneness to automation, rapid performance, amenability to integration, multiplexing, and cost‐effectiveness, is rapidly increasing for various sensing and energy harvesting applications. One such emerging area is the development of microfluidic fuel cell on cellulose papers, which has enormous scope to optimize its performance. This is primarily because such devices eliminate the need for membranes as well as external pumps since they have built‐in colaminar flow embedded capillaries. Such peripherals are usually used in conventional microfluidic fuel cells, which are fabricated using methods like photolithography, PDMS lithography, and 3D printing. This paper presents investigations on microfluidic paper–based fuel cells (MPFCs) with different cellulose absorbent pads for their performance optimization. Herein, the MPFC utilizes formic acid as fuel, oxygen from quiescent air as oxidant, and sulfuric acid as electrolyte for conducting ionic exchange under colaminar flow. The electrodes are realized through simple pencil strokes depositing a thin layer of graphite. The porous graphite electrodes act as diffusion agents breathing oxygen directly from the atmospheric air. Such an MPFC configuration, costing less than US $1, was optimized to achieve maximum energy density by examining various combinations of absorbent pads with different grades of cellulose papers. It is seen that the maximum open circuit potential is 0.46 V, while the maximum current and power densities are 1505.66 μAcm−2 and 173.97 μWcm−2, respectively, with a grade 6 absorbent pad. Such performance can be further enhanced by investigating MPFCs with various graphite pencils with a diverse number of strokes at different concentration levels.

Development of Membraneless Paper‐pencil Microfluidic Hydrazine Fuel Cell

“…Based on the design, the microchannel and absorbent pad of the hydrazine-hydrogen peroxide paper fuel cell with the optimized parameters were cut by the laser engraver. All the optimized cutting parameters are mentioned in our previous work [13]. In Hydrazine microfluidic fuel cell, a porous nature absorbent pad was used to control the flow within the cell.…”

“…Here, as shown in Table S1, smooth graphite HB and 8B pencils were used to create the graphite electrodes by manual scribing method on microchannel (Gr 3) with selected dimensions. The mass of the graphite electrodes (mass of graphite present on the porous paper) is reported in our previous work [13]. From the literature and experimental studies, it is evident that in case of pencil based electrodes, an anode of higher electrical resistance and cathode of lower electrical resistance provide the best performance values [26].…”

“…Finally, an absorbent pad, mounted at the end of the microfluidic fuel cell, was used to control the flow in a microfluidic fuel cell. The work covering the utility and optimization of such absorbent pads has been reported in our previous work [13].…”

“…Various anolytes, such as formic acid, methanol, ethanol, hydrazine etc., have been reported in microfluidic fuel cell platforms [11]. Rao et al investigated microfluidic paper fuel cells with formic acid, sulphuric acid, and oxygen acting as fuel, electrolyte, and oxidant, respectively wherein manually stroked graphite electrodes with varying numbers of pencil strokes and different types of filterpapers as absorbent pads were fabricated using HB and 8B grade pencils and maximum power density of 173.97 μWcm À 2 was achieved [12][13]. Arun et al examined a formic acid fuel cell with pencil stroked electrodes and atmospheric oxygen in a paper microchannel [14][15].…”

Single microfluidic fuel cell with three fuels – formic acid, glucose and microbes: A comparative performance investigation

“…Several techniques were used to fabricate portable miniaturized microfluidic devices, such as photolithography, soft-lithography [20], paper-based [21,22], xurography [23] and laser micromachining [24,25]. Despite their uniqueness and benefits, the development and implementtation of microfluidic fuel cells have not been utilized for portable electronic applications until now.…”