Current technologies for renewable energy such as biofuels or silicon-based solar cells are superior to fossil fuels in CO2 emissions. But they also have limitations like reliance on mining, recycling difficulties, and dependencies on farming and land use, resulting in biodiversity loss.
Researchers from the University of Cambridge, UK, have developed 3D-printed nano-skyscrapers that could help bacteria convert sunlight into energy. The novel method has the potential to increase sustainable fuel and bio-electricity in the future.
The team used 3D printing to create high-rise “building” grids where sun-loving cyanobacteria can grow and multiply quickly. Afterwards, they extracted the bacteria’s waste electrons – left over from photosynthesis – that could be used to power electronic devices.
“Our approach is a step towards making even more sustainable renewable energy devices for the future,” said Dr Jenny Zhang, lead researcher, Yusuf Hamied Department of Chemistry, University of Cambridge.
Cyanobacteria, also known as photosynthetic bacteria because of the way they multiply through sunlight, are one of the most abundant organisms on Earth. For years, researchers have been attempting to “re-wire” the photosynthetic mechanisms of the bacteria to harvest electrical energy from them.
Other scientists have harvested energy from cyanobacteria before, but the Cambridge researchers have found that providing them with the right kind of habitat increases the energy they can extract by over an order of magnitude.
“There’s been a bottleneck regarding how much energy you can extract from photosynthetic systems, but no one understood where the bottleneck was,” explained Zhang. “Most scientists assumed that the bottleneck was on the biological side, in the bacteria, but we’ve found that a substantial bottleneck is actually on the material side.”
Cyanobacteria need plenty of sunlight, like the surface of a lake in summer. And to extract the energy they produce through photosynthesis, the bacteria need to be connected to electrodes.
The Cambridge researchers’ 3D-printed nano-skyscrapers are made from metal oxide nanoparticles tailored to synergise with the bacteria as they perform photosynthesis. Like a tiny city, the structures were printed as highly branched, densely packed pillars.
“The electrodes have excellent light-handling properties, like a high-rise apartment with lots of windows,” Zhang added. “Cyanobacteria need something they can attach to and form a community with their neighbours. Our electrodes allow for a balance between lots of surface area and lots of light – like a glass skyscraper.”
According to Zhang and her team, their printing technique allows control over multiple scales, making the nano-skyscrapers highly customisable, which could benefit a wide range of fields.
“I was surprised we were able to achieve the numbers we did – similar numbers have been predicted for many years, but this is the first time these numbers have been shown experimentally,” she concluded.
