This bionic mushroom makes electricity | Science News for Students

This bionic mushroom makes electricity

Scientists had to figure out how to 3-D print bacteria onto a curved home of fungus
Feb 6, 2019 — 6:45 am EST
a photo of a green spiral of cyanobacteria printed onto a white mushroom marked with black graphene ink

Researchers 3-D print a green spiral of cyanobacteria onto a mushroom. The microbes give off electrons when exposed to light. Those electrons flow into the black graphene ink to produce an electric current.

American Chemical Society

This is one in a series presenting news on technology and innovation, made possible with generous support from the Lemelson Foundation.

Some bacteria have a superpower that scientists would love to harness. These microbes capture energy from light, just as plants do. Scientists have wanted to tap these bacteria to make electricity. But in previous research, they didn’t survive long on artificial surfaces. Researchers have now moved them to a living surface — a mushroom. Their creation is the first mushroom to make electricity.

Sudeep Joshi is an applied physicist. He works at the Stevens Institute of Technology in Hoboken, N.J. He and his colleagues turned that mushroom — a fungus — into a mini energy farm. This bionic mushroom combines 3-D printing, conductive ink and bacteria to generate electricity. Its design could lead to new ways of combining nature with electronics. 

Cyanobacteria (sometimes called blue-green algae) make their own food from sunlight. Like plants, they do this using photosynthesis — a process that splits water molecules, releasing electrons. The bacteria spit out many of these stray electrons. When enough electrons build up in one place, they can create an electrical current.

The researchers needed to clump a lot of these bacteria together. They decided to use 3-D printing to deposit them precisely onto a surface. Joshi’s team chose mushrooms for that surface. After all, they realized, mushrooms naturally host communities of bacteria and other microbes. Finding test subjects for their tests was easy. Joshi simply went to the grocery store and picked up white button mushrooms.

Printing on those mushrooms, though, turned out to be a real challenge. 3-D printers have been designed to print on flat surfaces. Mushroom caps are curved. The researchers spent months writing computer code to solve the problem. Eventually, they came up with a program to 3-D print their ink onto the curved mushroom tops.

an microscopic image of blue-green algae under a green filter
These cyanobacteria use photosynthesis to make food from sunlight. They are sometimes called blue-green algae.
Josef Reischig/Wikimedia Commons (CC BY SA 3.0)

The researchers printed two “inks” onto their mushrooms. One was a green ink made of cyanobacteria. They used this to make a spiral pattern on the cap. They also used a black ink made of graphene. Graphene is a thin sheet of carbon atoms that’s great at   conducting electricity. They printed this ink in a branching pattern across the mushroom top.

Then it was time to shine.

“Cyanobacteria are the real hero[es] here,” says Joshi. When his team shone light on the mushrooms, the microbes spit out electrons. Those electrons flowed into the graphene and created an electric current.

The team published their results November 7, 2018, in Nano Letters.

Current thinking

Experiments like this are called “proof of concept.” They confirm an idea is possible. The researchers showed their idea worked, even if it’s not yet ready for practical use. Achieving even this much took a few clever innovations. The first was getting the microbes to accept being rehoused on a mushroom. A second biggie: figuring out how to print them on a curved surface.

To date, Joshi’s group has generated a roughly 70 nanoamp current. That’s small. Really small. It’s about a 7-millionth the current needed to power a 60-watt light bulb. So clearly, bionic mushrooms won’t be powering our electronics right away.

Still, Joshi says, the results show the promise in combining living things (such as bacteria and mushrooms) with non-living materials (such as graphene).

It’s noteworthy that the researchers have convinced the microbes and mushrooms to cooperate for a short while, says Marin Sawa. She’s a chemical engineer at Imperial College London in England. Although she works with cyanobacteria, she was not part of the new study.

Pairing two life forms together is an exciting area of research in green electronics, she says. By green, she’s referring to an eco-friendly technology that limits waste.

The researchers printed cyanobacteria on two other surfaces: dead mushrooms and silicone. In each case, the microbes died out within about a day. They survived more than twice that long on the live mushrooms. Joshi thinks the microbes’ long life on the living mushroom is proof of symbiosis. That’s when two organisms coexist in a way that helps at least one of them.

But Sawa isn’t so sure. To be called symbiosis, she says the mushrooms and bacteria would have to live together a lot longer — at least a week.

Whatever you call it, Joshi wants thinks it’s worth tweaking. He thinks this system can be greatly improved. He’s been gathering ideas from other researchers. Some have suggested working with different mushrooms. Others have advised tweaking the genes of the cyanobacteria so that they make more electrons.

“Nature gives you lots of inspiration,” Joshi says. Common parts can work together to produce surprising results. Mushrooms and cyanobacteria grow in many places, and even graphene is just carbon, he notes. “You observe it, you come to the lab and start experiments. And then,” he says, if you’re really lucky “the light bulb will go off.”

Power Words

(more about Power Words)

3-D printing     A means of producing physical items — including toys, foods and even body parts — using a machine that takes instructions from a computer program. That program tells the machine how and where to lay down successive layers of some raw material (the “ink”) to create a three-dimensional object.

algae     Single-celled organisms, once considered plants (they aren’t). As aquatic organisms, they grow in water. Like green plants, they depend on sunlight to make their food.

atom     The basic unit of a chemical element. Atoms are made up of a dense nucleus that contains positively charged protons and uncharged neutrons. The nucleus is orbited by a cloud of negatively charged electrons.

bacteria     (singular: bacterium) Single-celled organisms. These dwell nearly everywhere on Earth, from the bottom of the sea to inside other living organisms (such as plants and animals).

carbon     The chemical element having the atomic number 6. It is the physical basis of all life on Earth. Carbon exists freely as graphite and diamond. It is an important part of coal, limestone and petroleum, and is capable of self-bonding, chemically, to form an enormous number of chemically, biologically and commercially important molecules.

chemical     A substance formed from two or more atoms that unite (bond) in a fixed proportion and structure. For example, water is a chemical made when two hydrogen atoms bond to one oxygen atom. Its chemical formula is H2O. Chemical also can be an adjective to describe properties of materials that are the result of various reactions between different compounds.

chemical engineer     A researcher who uses chemistry to solve problems related to the production of food, fuel, medicines and many other products.

code     (in computing) To use special language to write or revise a program that makes a computer do something.

coexist     To exist at the same time as or along with.

colleague     Someone who works with another; a co-worker or team member.

conductor     (in physics and engineering) A material through which an electrical current can flow.

current     (in electricity) The flow of electricity or the amount of charge moving through some material over a particular period of time.

cyanobacteria     A type of bacteria that can convert carbon dioxide into other molecules, including oxygen.

electric current     A flow of electric charge — electricity — usually from the movement of negatively charged particles, called electrons.

electricity     A flow of charge, usually from the movement of negatively charged particles, called electrons.

electron     A negatively charged particle, usually found orbiting the outer regions of an atom; also, the carrier of electricity within solids.

electronics     Devices that are powered by electricity but whose properties are controlled by the semiconductors or other circuitry that channel or gate the movement of electric charges.

engineer     A person who uses science to solve problems. As a verb, to engineer means to design a device, material or process that will solve some problem or unmet need.

fungus     (plural: fungi) One of a group of single- or multiple-celled organisms that reproduce via spores and feed on living or decaying organic matter. Examples include mold, yeasts and mushrooms.

gene     (adj. genetic) A segment of DNA that codes, or holds instructions, for a cell’s production of a protein. Offspring inherit genes from their parents. Genes influence how an organism looks and behaves.

graphene     A superthin, superstrong material made from a single-atom-thick layer of carbon atoms that are linked together.

green     (in chemistry and environmental science) An adjective to describe products and processes that will pose little or no harm to living things or the environment.

host      (in biology and medicine) The organism (or environment) in which some other thing resides. Humans may be a temporary host for food-poisoning germs or other infective agents.

innovation     (v. to innovate; adj. innovative) An adaptation or improvement to an existing idea, process or product that is new, clever, more effective or more practical.

microbe     Short for microorganism. A living thing that is too small to see with the unaided eye, including bacteria, some fungi and many other organisms such as amoebas. Most consist of a single cell.

molecule     An electrically neutral group of atoms that represents the smallest possible amount of a chemical compound. Molecules can be made of single types of atoms or of different types. For example, the oxygen in the air is made of two oxygen atoms (O2), but water is made of two hydrogen atoms and one oxygen atom (H2O).

nano     A prefix indicating a billionth. In the metric system of measurements, it’s often used as an abbreviation to refer to objects that are a billionth of a meter long or in diameter.

organism     Any living thing, from elephants and plants to bacteria and other types of single-celled life.

photosynthesis     (verb: photosynthesize) The process by which green plants and some other organisms use sunlight to produce foods from carbon dioxide and water.

physicist     A scientist who studies the nature and properties of matter and energy.

silicone     Heat-resistant substances that can be used in many different ways, including the rubber-like materials that provide a waterproof seal around windows and in aquariums. Some silicones serve as grease-like lubricants in cars and trucks. Most silicones, a type of molecule known as a polymer, are built around long chains of silicon and oxygen atoms.

subjects     (in research) The participants in a trial. The term usually refers to people who volunteered to take part. Some may receive money or other compensation for their participation, particularly if they entered the trial healthy.

symbiosis     (Adj. symbiotic) A relationship between two species that live in close contact. A species that lives this way, offering substantial help to the other species, is sometimes called a symbiont.

technology     The application of scientific knowledge for practical purposes, especially in industry — or the devices, processes and systems that result from those efforts.

waste     Any materials that are left over from biological or other systems that have no value, so they can be disposed of as trash or recycled for some new use.

watt     A measure of the rate of energy use, flux (or flow) or production. It is equivalent to one joule per second. It describes the rate of energy converted from one form to another — or moved — per unit of time. For instance, a kilowatt is 1,000 watts, and household energy use is typically measured and quantified in terms of kilowatt-hours, or the number of kilowatts used per hour.

Citation

Journal: S. Joshi et al. Bacterial nanobionics via 3D printing. Nano Letters. Vol. 18, published online November 7, 2018, p. 7448. doi: 10.1021/acs.nanolett.8b02642.