Ascorbic Acid Fuel Cell with a Microchannel Fabricated on Flexible Polyimide Substrate

Abstract

We used microelectromechanical system techniques to fabricate a miniature ascorbic acid fuel cell (AAFC) equipped with a microchannel for the circulation of ascorbic acid solution (AAS). The fuel cell was fabricated on a flexible polyimide substrate, and a porous carbon-coated aluminum (Al) anode with the dimensions of 2.8 ×1 mm 2 and a porous carbon-coated Al cathode with the dimension of 2.8 ×10 mm 2 were fabricated using photolithography and screen-printing techniques. The porous carbon was deposited by screen-printing carbon-black ink onto the Al electrode surfaces in order to increase the effective electrode surface areas and to absorb more enzymes (bilirubin oxidase) on the cathode surface. No enzyme was deposited on the carbon coated anode surface. The microchannel with a dimension of 3 ×11× 0.2 mm 3 was fabricated using a hot-embossing technique. The maximum power of 0.60 µW at 0.58 V, with a corresponding power density of 1.96 µW/cm 2 , was realized by introducing a 200 mM concentrated AA solution at the flow rate of 30 ml/min at room temperature. No degradation of the anode and cathode was observed up to the radius of curvature of 7.5 mm, which suggests the flexibility of the AAFC.

Miniaturized ascorbic acid fuel cells with flexible electrodes made of graphene-coated carbon fiber cloth

“…31) The power densities of the fructose BFCs reported by Miyake et al 23) and Haneda et al 30) were more than ten times greater than those of the glucose BFCs because fructose is much more reactive than glucose. The AAFC power density of 34.1 µW=cm 2 at 0.35 V in the 100 mM AA solution was larger than that of the previously reported AAFCs by Mogi et al 43) and Goto et al 48) Ultralow-power circuits for wireless sensor networking are strongly required for Internet of Things (IoT) society infrastructures, and extensive studies have been carried out to realize wireless transceiver=receiver systems that function at very low powers of less than 100 µW. 53) Ayers et al 54) reported an ultralow-power receiver for wireless sensor networks that functioned at 215 µW.…”

“…Goto et al 48) reported a portable BFC with porous carbon electrodes on a flexible PI substrate that was powered by a solid fuel unit made of solidified agarose hydrogel containing AA. However, the miniaturized AAFCs reported by Mogi et al 43) and Goto et al 48) exhibited much lower power density of between 1.08 and 1.96 µW=cm 2 at a relatively high AA fuel concentration of between 100 and 200 mM. Thus, these AAFCs require further improvement in their power density for their application as implantable AAFCs in in vivo environments.…”

“…42) Therefore, a power source with an area of cm 2 order, equivalent to the area of a current cardiac pacemaker, must exhibit a power density of 10 µW=cm 2 in an aqueous an AA solution with an AA concentration between 23 and 85 µM. Mogi et al 43) reported the fabrication and characterization of a miniaturized AAFC with a microchannel fabricated on a PI substrate using thermal nanoimprinting techniques [44][45][46][47] and MEMS technologies. However, they utilized porous carbon electrodes deposited on a flexible PI film, and these electrodes cracked after repeated bending of the BFC.…”

Overview of Materials for Microfluidic Applications

“…Polycyclo-olefin offers high moldability and low water uptake [19,20]. Polycarbonate [21] has excellent material toughness properties while polytetrafluoroethylene [22] and polyimide [23,24] feature excellent chemical resistance, electrical, and thermal properties, respectively. Polystyrene has become more and more involved for cellular-based microfluidic systems, due to its wide applications in cell biology.…”