Enzymatic biofuel cells designed for direct power generation from biofluids in living organisms

TLDR

Enzymatic biofuel cells promise direct use of biochemical energy in living organisms, but skin barriers and low internal oxygen limit their effectiveness. The study aims to fabricate a miniature assembly with a needle bioanode to access sugars through skin and a gas‑diffusion biocathode to capture atmospheric oxygen. The device employs a needle bioanode and gas‑diffusion biocathode, and its performance was tested by inserting a glucose‑oxidizing needle into a rabbit ear blood vessel. Optimizing biocathode hydrophobicity quadrupled its performance, the assembled device produced 26.5 µW in a grape and powered an LED as a sugar indicator, and anti‑biofouling coating stabilized power output in rabbit blood.

Abstract

Enzymatic biofuel cells have attracted much attention for their potential to directly use biochemical energy sources in living organisms such as animals, fruits, etc. However, generally natural organisms have a skin, and the oxygen concentration in the organisms is lower than that of biofuels like sugars. Here, we fabricated a novel miniature assembly that consists of a needle bioanode for accessing biofuels in organisms through their skins and a gas-diffusion biocathode for utilizing the abundant oxygen in air. The performance of the biocathode was fourfold improved by optimizing its hydrophobicity. The assembled device with four needle anodes for fructose oxidation was inserted into a raw grape, producing a maximum power of 26.5 μW (115 μW cm−2) at 0.34 V. A light-emitting diode (LED) with the cell served as a self-powered indicator of the sugar level in the grape. Power generation from blood sugar was also investigated by inserting a needle anode for glucose oxidation into a blood vessel in a rabbit ear. Prior coating of the tip of the needle anode with an anti-biofouling agent was effective to stabilize the output power.