Electrocatalyst Evaluation of 3D Printed Microfluidic Membraneless Glucose Biofuel Cell with Integrated Pencil Graphite Electrodes

Abstract

This work demonstrates for the first time the application of Pencil Graphite (PG) based enzyme nano biocomposite electrode substrates for a membraneless glucose biofuel Cell (GBFC) in a microfluidic environment [1]. PG is non-toxic, user friendly and prone to the environment with good mechanical rigidity and chemical inertness making it biocompatible. Low background currents, strong adsorption properties, wide potential window, good sensitivity and reproducibility, adjustable electro active surface area and ease of miniaturization make it an excellent candidate to employ as a working electrode [2]. A time-efficient and cost-effective process is proposed involving simple and easy steps for the fabrication of the PG electrodes [3]. After screening various grades of pencil leads, bioanode was fabricated from B grade PG by substantially increasing its surface area by coating carboxylated multiwalled carbon nanotube (MWCNT) through dipping method followed by the covalent immobilization of the anodic catalyst, glucose oxidase enzyme [4]. Likewise, the biocathode was fabricated from 5H grade PG by coating carboxylated multiwalled carbon nanotube through dipping method and electrodeposition of polyaniline (PANI) coating followed by the covalent immobilization of the cathodic catalyst, Laccase enzyme [5]. These electrodes were then inserted into a microfluidic co-laminar flow based membraneless GBFC as shown in Fig. 1a., designed and fabricated using a 3D printer. Glucose was used as fuel and air as oxidant with p-Benzoquinone (PBQ) and 2, 2- azino-bis (3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) in solubilized form as anodic and cathodic mediators respectively and the eletrochemical charecteristics were measured using polarization studies under pysiological glucose concentation conditions (40 mM, 37ºC, pH 7.0) by varying the flow rates, dimensions of the device and distance between electrodes. This portable microfluidic set up generated maximum power density of 10 μWcm-2, OCP of 500±5 mV and current density 64 μA cm-2 at a flow rate of 40 μlmin-1 which could sustain for more than 100 hours. Hence, this work successfully demonstrates the strong potential of using readily available and biocompatible PGs as low cost alternatives to carbon based electrodes to power miniaturized low temperature microelectronic devices and sensors. Figure 1