They may be better known for stir-fries than supercomputing, but shiitake mushrooms have now been harnessed to function as living processors, storing and recalling data like a semiconductor chip but with almost no environmental footprint.

Scientists at Ohio State University have shown that fungi can be trained to act like memristors – microscopic components used to process and store data in computer chips. The team found that shiitake-based devices demonstrated similar reproducible memory effects to semiconductor-based chips and could be used to create other types of low-cost, environmentally friendly, neural-inspired components.

“Being able to develop microchips that mimic actual neural activity means you don’t need a lot of power for standby or when the machine isn’t being used,” said lead author John LaRocco, a research scientist at Ohio State’s College of Medicine. “That’s something that can be a huge potential computational and economic advantage.”

A memristor (“memory resistor“) is a circuit element that changes its resistance depending on how much current has passed through it – essentially, it remembers past electrical activity. Traditional memristors are made from metal oxides or silicon and require rare-earth minerals, high-temperature production and a lot of power to run. By contrast, fungal mycelium – the underground network of filaments that helps mushrooms feed and communicate – can be grown at room temperature and, at the end of their life cycle, be easily composted.

“Mycelium as a computing substrate has been explored before in less intuitive setups, but our work tries to push one of these memristive systems to its limits,” added LaRocco.

The researchers cultivated shiitake and button mushrooms on an organic substrate in Petri dishes until the sample was covered with a dense mycelial mat. These mats were then dehydrated and connected to electronic circuits. When voltages were applied – from 10 Hz to 5,850 Hz – the mushroom circuits began to behave like organic memristors.

Each cultured sample grew a mycelial network that was connected to conventional electronics

John LaRocco/Ohio State University

“We would connect electrical wires and probes at different points on the mushrooms because distinct parts of it have different electrical properties,” said LaRocco. “Depending on the voltage and connectivity, we were seeing different performances.”

After two months, the team discovered that when used as RAM, the mushroom memristor was able to switch between electrical states – and hold onto that information – at up to 5,850 signals per second, with around 90% accuracy. At low frequencies, it achieved up to 95% switching accuracy. Performance dropped as the frequency of voltages increased, but this could be remedied by connecting more fungi to the circuit.

While mushroom-based electronics aren’t entirely new, scientists have become increasingly interested in using fungi for computing and energy production. Mycelium forms a self-repairing, three-dimensional grid that transmits electrical impulses in response to stimuli, not unlike neurons in a brain. Unlike silicon, this kind of organic system is flexible, scalable and capable of growing into new configurations. And, of course, it’s much more eco-friendly than current synthetic models.

“Society has become increasingly aware of the need to protect our environment and ensure that we preserve it for future generations,” said co-author Qudsia Tahmina, an associate professor in electrical and computer engineering at Ohio State. “So that could be one of the driving factors behind new bio-friendly ideas like these.”

While it’s still early days for organic memristors, the researchers plan to look at ways of growing fungi that would shrink the devices to a size they’d need to be for real-world use. Researchers are already working on using fungi for batteries and for generating electricity.

“Everything you’d need to start exploring fungi and computing could be as small as a compost heap and some homemade electronics, or as big as a culturing factory with pre-made templates,” said LaRocco. “All of them are viable with the resources we have in front of us now.”

The research was published in the journal PLOS One.

Source: Ohio State University