Using Mushrooms to Control Robots

Andrew Corselli

In creating a pair of new robots, Cornell researchers cultivated an unlikely component, one found not in the lab but on the forest floor: fungal mycelia. By harnessing mycelia’s innate electrical signals, the researchers discovered a new way of controlling “biohybrid” robots that can potentially react to their environment better than their purely synthetic counterparts.

“This paper is the first of many that will use the fungal kingdom to provide environmental sensing and command signals to robots to improve their levels of autonomy,” said Senior Author Rob Shepherd, Professor of Mechanical and Aerospace Engineering in Cornell Engineering. “By growing mycelium into the electronics of a robot, we were able to allow the biohybrid machine to sense and respond to the environment. In this case we used light as the input, but in the future it will be chemical. The potential for future robots could be to sense soil chemistry in row crops and decide when to add more fertilizer, for example, perhaps mitigating downstream effects of agriculture like harmful algal blooms.”

In designing the robots of tomorrow, engineers have taken many of their cues from the animal kingdom, with machines that mimic the way living creatures move, sense their environment and even regulate their internal temperature through perspiration. Some robots have incorporated living material, such as cells from muscle tissue, but those complex biological systems are difficult to keep healthy and functional.

Mycelia are the underground vegetative part of mushrooms, and they have a number of advantages. They can grow in harsh conditions. They also have the ability to sense chemical and biological signals and respond to multiple inputs.

“If you think about a synthetic system — let’s say, any passive sensor — we just use it for one purpose. But living systems respond to touch, they respond to light, they respond to heat, they respond to even some unknowns, like signals,” said Lead Author Anand Mishra, Research Associate in the Organic Robotics Lab led by Shepherd. “That’s why we think, ‘OK, if you wanted to build future robots, how can they work in an unexpected environment?’ We can leverage these living systems, and any unknown input comes in, the robot will respond to that.”

However, finding a way to integrate mushrooms and robots requires more than just tech savvy and a green thumb.

“You have to have a background in mechanical engineering, electronics, some mycology, some neurobiology, some kind of signal processing,” Mishra said. “All these fields come together to build this kind of system.”

Mishra collaborated with a range of interdisciplinary researchers. He consulted with Bruce Johnson, Senior Research Associate in Neurobiology and Behavior, and learned how to record the electrical signals that are carried in the neuron-like ionic channels in the mycelia membrane. Kathie Hodge, Associate Professor of Plant Pathology and Plant-Microbe Biology in the School of Integrative Plant Science in the College of Agriculture and Life Sciences, taught Mishra how to grow clean mycelia cultures, because contamination turns out to be quite a challenge when you are sticking electrodes in fungus.

The system Mishra developed consists of an electrical interface that blocks out vibration and electromagnetic interference and accurately records and processes the mycelia’s electrophysiological activity in real time, and a controller inspired by central pattern generators — a kind of neural circuit. Essentially, the system reads the raw electrical signal, processes it, and identifies the mycelia’s rhythmic spikes, then converts that information into a digital control signal, which is sent to the robot’s actuators.

Two biohybrid robots were built: a soft robot shaped like a spider and a wheeled bot.

The robots completed three experiments. In the first, the robots walked and rolled, respectively, as a response to the natural continuous spikes in the mycelia’s signal. Then the researchers stimulated the robots with ultraviolet light, which caused them to change their gaits, demonstrating mycelia’s ability to react to their environment. In the third scenario, the researchers were able to override the mycelia’s native signal entirely.

Here is an exclusive Tech Briefs interview, edited for length and clarity, with Mishra.

Tech Briefs: What was the biggest technical challenge you faced while developing these biohybrid robots?

Mishra: The biggest technical challenge is to make sure you are reading the true signal because the robot is moving. These mycelium electrical signals are very small, they're about a microvolt. You want to make sure that you don't pick up any kind of noise due to the mechanical input while moving. And then you want to make sure that you don't pick up any noise due to electromagnetic interference, because sometimes you might get 50 or 60 Hz noise.

Of course, there are more challenges. You have to make sure the electrodes have been properly positioned so that the electrode can easily interface, or the mycelia can grow with the electrode. Both robotic systems are designed very differently. But I think the biggest challenge is noise — making sure that you're reading the mycelium signal.

Tech Briefs: Can you explain in simple terms how it works?

Mishra: Mycelium has these action potential-like signals. Most likely that comes from some kind of ionic channels inside their cytoplast. And sometimes there is a calcium or potassium flux, which causes a spike. What we did is we just used every spike that came in; we studied that and estimated the width and the time. We mapped that to a digital signal because computers cannot understand pure analog signals — and then we sent it to the actuators or the motors. Then, every spike you see has this corresponding digital signal, and then that has the corresponding mechanical movement.

It's like how we work — the motor command. Our brain sends the motor command, the action potential waveform, and the muscle moves. So that's what we were trying to do. Every signal has a corresponding locomotion movement. And then, since it's rhythmic, the robot can move forward or backward based on the rhythms.

There are two kinds of signals we utilize. One is the native signal that is coming from the mycelium itself. The other is a stimulated signal, where we use UV light to stimulate it; we use it to either override the mycelium signal using just the microcontroller or just use the stimulated signal to alter the gate or change the direction.

Tech Briefs: What are your next steps? Do you have plans for further research work, etc.?

Mishra: Yes, of course. This is a new way of how we can interface living systems with machines. One of our interests is to understand chemical cues. We want to bring this whole system into agricultural spaces and do some kind of biochemical signaling, which is not possible through mostly synthetic systems or synthetic materials.

Our idea is to use these kinds of robots to study soil, do we can predict if there is a nutrition deficiency or some specific chemical is missing. So, we wanted to use a living system to do it for us — they’re definitely better than whatever synthetic system we can use.

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