Small-scale, storable paper biobatteries activated via human bodily fluids

Herein, a fully paper-based biobattery composed of four microbial fuel cell (MFC) units is evaluated, one that can be prepared in advance, stored, and quickly activated with virtually any available fluid. The biobattery uniquely utilizes Bacillus subtilis endospores as the storable anodic biocatalyst; the dormant, robust nature of B. subtilis endospores should allow for device preinoculation with spores followed by prolonged storage of the fully fabricated paper battery until needed. A germinant paper layer strategically fabricated above the spore-loaded anode layer contains all of the necessary chemical germinants and nutrient components required for the endospores to begin germination, exit dormancy, and return to fully metabolic vegetative bacterial cells that can generate electrical energy. This mechanism allows for the battery to be simply initiated via a wide range of available liquids. Bioelectricity generation of the battery is successfully demonstrated after introduction of a variety of artificial bodily fluids, including saliva, sweat, and urine, along with tap water. Since the biobattery has the capability of serially linking all 4 of its MFCs through simple dynamic folding, the device’s total power output can be greatly enhanced; a single biobattery is able to achieve 0.56 V and 2.4 μW, which is beyond the ratings required for their intended application in single-use, disposable sensors. Therefore, this concept of integrating 4 spore-based MFCs into a single biobattery device with a built-in germinant layer offers a potential solution for stable, long-term storable power sources, displaying feasibility for integration with low power, disposable sensor applications.