MICROBIAL FIBER POWER: BIG THINGS HAVE SMALL BEGINNINGS

For the hundredth time, the measured current-voltage curve on the screen remained flat. Perhaps the sceptics were right after all: while chemical data suggested that the strange bacteria found in the seafloor could conduct electricity, maybe they didn’t after all. Pulling them out of the sediment, carefully cleaning them, positioning them on a nanoelectrode device, and hoping for a current was never going to work. Trial after trial failed – there was no sign of conductance to be seen.

“And then suddenly, the flat line transforms into a steep curve on the computer screen, and that was the real Eureka moment”

recalls Filip Meysman, professor of biology at the University of Antwerp, Belgium. “The current was incredibly high and we immediately realised there was something incredibly conductive inside the bacteria.”

Professor Meysman and his colleagues had come a long way and endured many disappointments. But the effort was worthwhile. Finding a material that is biodegradable and highly conductive at the same time is one of the genuine holy grails in material science that has been chased for a very long time. The demonstration of high conductance in the very long “cable bacteria” extracted from the seafloor finally provided the breakthrough; a future with cleaner, greener electrical components was no longer far-fetched.

Novel biological electronic technology

Meysman leads the PRiNGLE project (Protein-based Generation Electronics), which focuses on developing a wholly new class of biobased materials with tailored electronic properties, intended for integration into electronic devices. Funded by a €3.2m European Innovation Council (EIC) PathFinder grant, the is working to establish a field of an all-biologic electronic technology (proteonics) to produce biodegradable components for sensors, devices, and likely some objects yet to be invented, all produced with less energy and less waste compared to conventional processes.

“The challenge is substantial because the materials currently used in electronics, like those in our smartphones, are metal-based, plastic-based, or silicon-based,” says Meysman. “The environmental footprint of electronics is huge, and this is exactly what we want to change.” Big challenges like this require significant funding mechanisms that drive deep-tech solutions to address societal challenges, and this is what EIC Communities projects do.

With global population rising past eight billion and ever more people having access to more electronic devices, from phones to tablets, e-watches and battery-powered vehicles, the electronics industry generates over 50 million tonnes of electronic waste (e-waste) annually, which is growing at a rate of 5% each year, much faster than the other types of municipal waste.

The best of both worlds

This is where biomaterials have a clear advantage. We are all familiar with the beneficial properties of natural biological fibers, like silk, wool, and cotton. You can spin them into fibers, and they are highly flexible and strong. Alas, traditional biomaterials have one major disadvantage: they are very poorly conductive, and so they cannot be used for electronics.

This is why the discovery of high conductance in the centimetre-long, multicellular ‘cable’ bacteria from the ocean floor is such a major breakthrough. “We found an organic biostructure that conducts electricity in an incredibly efficient way,” says Meysman. “The cable bacteria are very long, thin threads that send electricity from one end to the other at an amazing rate. The conductivity is almost that of a metal.”

The key problem was to determine how the bacteria were accomplishing this feat. This was far from easy. Foremost, it turned out to be very difficult to grow the cable bacteria in the lab.

“Cable bacteria live very happily in black, stinky mud of the seafloor, but they are difficult to grow in the lab.”

Metsman explains. It took many years to find out how to culture them, isolate them from the sediment, and contact them with nanoelectrodes before they could even start to measure their electrical conductivity.

“We had to invent new tools. These bacteria are a hundred times thinner than a human hair, you have to hook them and wash them, all under the microscope,” says Meysman. “It’s all difficult and very laborious, and requires very minute instruments, but we managed and interconnected the cable bacteria to nanoelectrodes.”

New approaches were tried, different techniques and technologies came and went, but still the current-voltage line of the screen remained flat: until that very Eureka moment. Meysman’s team at UAntwerpen had started collaborating with a group of theoretical physicists from Delft University of Technology (TU Delft), experts in using tiny probes and measuring the electrical properties of other nanostructures like graphene. When they applied their expertise to the mysterious fibres from the seabed, the flat line eventually became a curve. This close collaboration between biologists and physicists demonstrates the power of multidisciplinary teams across Europe working together with the right support and funding.

Teamwork makes the dream work

Now three years into the four-year PRiNGLE project, the consortium of six partners from five different countries is deciphering just how it all works.

“The conduction mechanism that cable bacteria have evolved 500 million years ago is simply mind-blowing. It’s based on new biochemistry, also new quantum physics, which makes it all very exciting,” explains Meysman. “This novelty also makes the research difficult, because you are operating in uncharted territory. It’s like when you are dropped in the middle of a rainforest, and there is no map. It’s the organism that decides on what research to be done, it’s not you.”

“However, the extreme novelty of the conductive biomaterial that we discovered also entails great promise for future green electronic applications,” says Meysman.

“The fact that we have now a biomaterial with extraordinary electric properties opens a cascade of opportunities for applications.”

The objective of the PRiNGLE project is to translate the breakthrough discovery as fast as possible into technology. Within the interdisciplinary consortium, coordinated by UAntwerp, Delft University of Technology is characterising the extraordinary electrical properties of the material, while the University of Cyprus is performing electron transport simulations, Flanders Institute of Biotechnology is charting out how to make the material in vitro. Likewise, the Forschungszentrum Jülich examines how materials can be integrated into bio-electronic devices, while the Institute for Bioengineering of Catalonia (IBEC) is performing nanoscale characterisation to assess which future applications are most promising.

Meysman says the project’s journey has been a fascinating ride, with many surprising twists and turns.  He is grateful for the support and patience of the EIC and its project officers.

“When you ask mother nature questions, you do not always receive the answer you initially expected. But it is exactly the highly unexpected findings that provide the Eureka moments and the greatest science-to-technology breakthroughs.”

Photo by ilgmyzin on Unsplash