Rechargeable membraneless glucose biobattery: Towards solid-state cathodes for implantable enzymatic devices.

Enzymatic biobatteries can be implanted in living organisms to exploit the chemical energy stored in physiological fluids. Generally, commonly-used electron donors (such as sugars) are ubiquitous in physiological environments, while electron acceptors such as oxygen are limited due to many factors including solubility, temperature, and pressure. The wide range of solid-state cathodes, however, may replace the need for oxygen breathing electrodes and serve in enzymatic biobatteries for implantable devices. Here, we have fabricated a glucose biobattery suitable for in vivo applications employing a glucose oxidase (GOx) anode coupled to a solid-state Prussian Blue (PB) thin-film cathode. PB is a non-toxic material and its electrochemistry enables fast regeneration if used in a secondary cell. This novel biobattery can effectively operate in a membraneless architecture as PB can reduce the peroxide produced by some oxidase enzymes. The resulting biobattery delivers a maximum power and current density of 44 μW cm−2 and 0.9 mA cm−2, respectively, which is ca. 37% and 180% higher than an equivalent enzymatic fuel cell equipped with a bilirubin oxidase cathode. Moreover, the biobattery demonstrated a stable performance over 20 cycles of charging and discharging periods with only ca. 3% loss of operating voltage.