Pee-Powered Microbial Fuel Cell Socks Are Here To Save Wearable Technology

How's this for a truly excellent journal article title? "Self-sufficient Wireless Transmitter Powered by Foot-pumped Urine Operating Wearable MFC."

Said report appears in the current issue of Bioinspiration and Biomimetics and it is as advertised, describing a new technology that generates electricity via pee-powered microbial fuel cell socks. The system, which is inspired by the circulatory systems of fish, is able to power a wireless transmission board tasked with sending data every two minutes to a PC receiver module. Pee, bacteria, wearable technology—this is great stuff.

"Portable and wearable devices are progressing at an accelerated pace and are thus becoming more available on the mainstream market," the study notes. "Despite the advances in ultra-low power electronics, powering those systems still poses a significant challenge."

Continuing on: "In addressing this issue, attention has been given to alternative energy sources such as electromagnetic, solar, thermal, and mechanical. Using unwanted waste products, as a source of chemical energy, can be considered as an alternative method for such systems, particularly taking into account that it can be available for humans in a variety of environments."

The idea of a pee-based microbial fuel cell isn't new, not even as a mechanism for powering wearable technology. The basic idea of the urine fuel cell (or any fuel cell based on "wet organic waste products" is that microbes are able to break down the organic compounds within urine, bits of proteins and hormones, and this process releases carbon-dioxide with protons and electrons. Shuttle those electrons away via a circuit and you have some electricity.

The catch is that this mechanism doesn't produce all that much power, which means that whatever pumping mechanism is used to provide the cells with urine needs to be very low-energy. This is where the authors of the current study looked to fish.

Fish have pretty simple circulatory systems, relatively speaking. A fish heart has only two chambers, one atrium and one ventricle, and so the fish only has a single blood circuit. Flap-like connective tissues known as ostial valves keep blood from flowing backward between the two chambers, as muscles surrounding the heart provide the pressure needed to keep blood flowing while also providing suction within the system to keep it from leaking.

The authors of the current study realized that they could accomplish something like this by swapping in regular footsteps for muscular contractions and by using a similar set of one-way valves. So, energy that would have been expended anyway as walking is employed as the fish heartbeat that keeps urine flowing around a pair of socks lined with microbe-laden chambers. Finally, the fuel-cell socks are connected to a wireless transmitter.

It turns out that this system could one day save your life. "It is then possible to envisage wearable transmission systems that have a purpose of transmitting a person's coordinates, in e.g. a case of emergency, which can operate when fed with just urine," the study explains. "A venture in this direction not only widens the range of applications that [microbial fuel cells] could be implemented in, but also introduces the concept of built-in 'proof of life' capability, since the device will only operate if the person wearing it, urinates inside it."