Stretch batteries

An entirely textile-based, bacteria-powered bio-battery could be used in wearable electronics, according to researchers at Binghamton University, State University of New York, USA, and their colleagues.

Seokheun Choi and his team have built a bio-battery that can produce a maximum power on a par with that produced by the team's previous paper-based microbial fuel cell. Moreover, the textile-based bio-batteries have a stable capacity to generate electricity even after many attempts to damage them by stretching and twisting them. Choi suggests that this stretchable, twistable power device could establish a standardized platform for textile-based bio-batteries and will be potentially integrated into wearable electronics in the future.

"There is a clear and pressing need for flexible and stretchable electronics that can be easily integrated with a wide range of surroundings to collect real-time information," explains Choi. "Those electronics must perform reliably even while intimately used on substrates with complex and curvilinear shapes, like moving body parts or organs. We considered a flexible, stretchable, miniaturized bio-battery as a truly useful energy technology because of their sustainable, renewable and eco-friendly capabilities."

The team points out that when compared to conventional batteries and even enzymatic fuel cells, microbial fuel cells offer many more advantages in the realm of wearable electronics. This is because the whole microbial cell acts as a biocatalyst providing stable enzymatic reactions and a long life span. It might even be possible to simply use sweat produced by the person's body to fuel such a bio-battery rather than having to rely on an external fuel supply such as methanol or a biogas. Sweat readily supports bacterial communities on our skin, this technology would simply be mopping up the energy inherent in the human body's excretory cooling system.

"If we consider that humans possess more bacterial cells than human cells in their bodies, the direct use of bacterial cells as a power resource interdependently with the human body is conceivable for wearable electronics," adds Choi.

In their paper, the team explains details of how they used the microbe Pseudomonas aeruginosa (PAO1) to generate a maximum power of 6.4 microwatts per square centimeter of their flexible microbial fuel cell. Moreover, it produces a current density of 52 microamps per square centimeter. [Choi et al., Adv. Energy Mater., (2017), 1702261; DOI: 10.1002/aenm.201702261]

The team adds that fabrication is relatively simple as they have reduced the complexity of the bio-battery by using a single-chamber configuration that lacks a membrane. Instead, the device contains its conductive and hydrophilic anode in a 3D fabric microchamber. This also maximizes bacterial electricity generation from a liquid environment. The device's silver oxide/silver solid-state cathode reduces cathodic overpotential for fast catalytic reactions.

David Bradley blogs at Sciencebase Science Blog and tweets @sciencebase.