Bacteria Ride Bionic Mushrooms to Generate Electricity

Bacterial nanobionics offers applications from sensors to smart materials

Photograph of a white button mushroom equipped with 3D- printed graphene nanoribbons (black), which collect electricity generated by densely packed 3D-printed cyanobacteria (green).
Photo: Sudeep Joshi/Stevens Institute of Technology
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What do you get when you combine the high-tech world’s “wonder material”—graphene—with a lowly fungus? A bionic mushroom, of course.

Researchers at the Stevens Institute of Technology have reported in the journal Nano Letters the seamless merging of cyanobacterial cells and graphene nanoribbons on the cap of a mushroom. The resulting combination represents a three-dimensional interface between the microbiological kingdom (cyanobacteria and mushroom) and smart electronic nanomaterial (graphene nanoribbons).

The researchers believe that this approach—which they refer to as bacterial nanobionics—can spur the development of next-generation "designer bio-hybrid" functional architectures for applications ranging from sensors to “smart” hydrogel materials.     

To develop their bionic mushroom, the Stevens researchers first looked for a way to lengthen the lifespan of the cyanobacteria. While cyanobacteria has an amazing ability to produce electricity, it also has a notoriously short life cycle severely limiting its usefulness. By putting the cyanobacteria on the cap of a mushroom, the researchers extended the life cycle of the cyanobacteria to several days.

Next, they developed a way to harvest the electricity cyanobacteria produce by printing electronic ink containing graphene nanoribbons onto the mushroom cap.

“These graphene nanoribbons form substantial voluminous direct physical attachment sites with the outer membrane of cyanobacterial cells,” said Sudeep Joshi, a postdoctoral fellow at Stevens and co-author of the research “Imagine needles sticking into a single bacterial cell to access electrical signals inside it.”

When light is focused on the graphene-clad mushroom cap, the cyanobacteria perform photosynthesis. Electrons are released as a by-product during the cleavage of water molecules. At this point, the graphene nanoribbons attached to the cyanobacteria act as a conductive network to transfer these electrons to the external circuitry in an electrochemical cell set-up. 

Sudeep Joshi, a postdoctoral fellow at Stevens and co-author of the research, and his colleagues believe that are many opportunities and applications for 3D printed bacterial nanobionics. These applications would leverage the unique capabilities of different bacteria, such as bio-luminescence, sensing of toxins, or in this case photosynthesis.

“We believe that techniques developed in our present research can also be extended to 3D print other bacterial colonies with smart hydrogel materials for advancing bionic integration studies,” said Joshi. “Moreover, we envisage that this 3D printing bacterial nanobionics approach can organize different bacterial species in complex arrangements to investigate spatial and environmental parameters for influencing other bacterial social behaviors, such as bioluminescence and virulence.”

Along these lines, Joshi and his colleagues will continue to apply their approach to other bacterial species for monitoring and controlling the effect of spatial geometry and population density. Specifically, they will be looking at the microbiota present in the guts, skin, intestine and mouth of humans.

Joshi added: “Population density of microbes in these microbiotas are directly linked to the health and well-being of an individual. We are specifically looking forward to engineering the human microbiota and its effect on well-being of humans via “bacterial nanobionics.”

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