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Paper devices are cutting‐edge platforms for creating miniaturized energy conversion, storage, and sensing devices. In such devices, co‐laminar flow and embedded capillaries not only eliminate membranes and external pumps but also allow widespread application. The fabrication, optimization, and characterization of a microfluidic paper ethanol fuel cell (MPEFC) has been demonstrated in the presented study. The MPEFC uses ethanol and sodium hydroxide as fuel and sulfuric acid as electrolytes. Numerous experiments have been conducted to improve the performance of MPEFC by optimizing various electrode types such as laser‐induced graphene (LIG), Ag nano‐ink/LIG, buckypaper, Ag nano‐ink/buckypaper, and two different 3D printed conductive electrodes. Different electrolyte concentrations (NaOH‐0.25, 0.5, 1 m) have been studied to understand the impact on ion conductivity. It is observed that the developed MPEFC with multiwalled carbon nanotube ‐buckypaper as an optimized electrode, 1 M ethanol with 0.5 m NaOH as anolyte, and 1 m H2SO4 as electrolyte delivered the best performance with a current density of 1756.2 μA cm−2, and power density of 72.62 μW cm−2, at a stable open‐circuit voltage of 235 mV with Gr 1 cellulose microchannel with parallel stacked configuration. This work demonstrates the effective enhancement of the output power with inexpensive individual MPEFC. [ABSTRACT FROM AUTHOR]

Summary: Paper microfluidic devices are innovative platforms for building miniaturized devices for energy harvesting, energy storage, and sensing applications. Such devices are reported to be used as membraneless microfluidic fuel cells to power portable electronic in a pump‐less manner by leveraging the embedded capillaries and co‐laminar flow. This paper demonstrates fabrication and characterization of the high‐performance metal‐free aluminum‐air microfluidic paper fuel cell (AAMPFC). Herein, aluminum foil acts as an anode, buckypaper with built‐in multiwalled carbon nanotubes (MWCNTs) acts as a cathode and sodium hydroxide (NaOH) works as an electrolyte. The novel AAMPFC is analyzed with various electrolyte concentrations, and maximum output voltage, current density, and power density are recorded. This easy‐to‐fabricate AAMPFC platform, costing less than US$ 0.5, is further optimized to achieve peak energies by stacking four AAMPFCs (in series and parallel) with various concentrations of electrolyte (NaOH). With parallel configuration, maximum open‐circuit potential (OCP), peak current (mA/cm2), and power density (mW/cm2) of 1.32 V, 50.67 mA/cm2 and 22.80 mW/cm2, respectively, are observed with optimized electrolyte, while with series stacked configuration, a stable OCP of 4.10 V is measured. In a series configuration, AAMPFC generated sufficient power to powering a scientific calculator with LCD display for 3 days and 11 LEDs for 10 hours continuously. This research work provides a significant method to enhance the output power with inexpensive parameters (buckypaper, single paper microchannel) to power portable electronic devices. Further, the performance can be enhanced by investigating AAMPFC with various grades of aluminum foil in combination with different grades of porous cellulose papers. [ABSTRACT FROM AUTHOR]

Herein, a membraneless paper based co‐laminar microfluidic Hydrazine‐Hydrogen peroxide fuel cell, employing graphite pencil electrode, is presented. Hydrogen peroxide has been used as oxidant while sulphuric acid and sodium hydroxide have been employed as electrolytes. The electrodes were formed by manual stroking of graphite pencils. Maximum power output was achieved by examining various combinations of different grades of graphite electrodes on a suitable filter paper with 100 pencil strokes. Here, maximum current density and power density of 14.43 μA/cm2 and 1.30 μW/cm2 respectively were achieved at a stable open circuit potential of 410 mV for 40 mM of hydrazine concentration. [ABSTRACT FROM AUTHOR]