Biohybrid robots controlled by electrical impulses in mushrooms

Building a robot takes time, technical skills, the right materials, and sometimes, a little fungus.

In creating two new robots, Cornell researchers cultivated an unlikely compound found not in the lab but on the forest floor: fungal mycelium. By harnessing the mycelium’s innate electrical signals, the researchers have discovered a new way to control “biohybrid” robots that can potentially respond to their environment better than their purely synthetic counterparts.

The team’s paper, “Sensorimotor control of robots achieved through electrophysiological measurements of fungal mycelia,” is published in Scientific roboticsThe lead author is Anand Mishra, a research associate in the Organic Robotics Lab led by Rob Shepherd, professor of mechanical and aerospace engineering at Cornell Engineering, and senior author of the paper.

“This work is the first of many that will use the fungal kingdom to provide environmental sensing and control signals to robots to improve their level of autonomy,” Shepherd said. “By growing mycelium in a robot’s electronics, we were able to enable the biohybrid machine to sense and respond to the environment. In this case, we used light as an 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, to perhaps mitigate downstream effects of agriculture like harmful algae blooms.”

To design the robots of tomorrow, engineers have looked to the animal kingdom for inspiration, with machines that mimic the way living things move, sense their environment, and even regulate their internal temperature through sweat. Some robots have incorporated living materials, such as muscle cells, but these complex biological systems are difficult to keep healthy and functional. It’s not always easy, after all, to keep a robot alive.

Mycelia are the underground vegetative part of fungi and have many 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, say any passive sensor, we use it for one purpose only. But living systems respond to touch, light, heat, and even some unknowns, like signals,” Mishra said. “So we asked ourselves, ‘OK, if you want to build robots of the future, how can they operate in an unexpected environment?’ We can harness these living systems, and for every unknown input, the robot will respond.”

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

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

Mishra collaborated with an interdisciplinary group of researchers. He consulted with Bruce Johnson, a senior research associate in neurobiology and behavior, and learned how to record electrical signals carried in neuronal-like ion channels in the mycelium membrane. Kathie Hodge, an associate professor of plant pathology and plant and microbial biology in the School of Integrative Plant Science in the College of Agriculture and Life Sciences, taught Mishra how to grow clean mycelium cultures, since contamination is a challenge when you stick electrodes into mushrooms.

The system Mishra developed consists of an electrical interface that blocks vibrations and electromagnetic interference and accurately records and processes the electrophysiological activity of the mycelium in real time, as well as 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 rhythmic spikes of the mycelium, then converts this information into a digital control signal, which is sent to the robot’s actuators.

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

The robots performed three experiments. In the first, the robots walked and rolled, respectively, in response to natural, continuous spikes in the mycelium’s signal. The researchers then stimulated the robots with ultraviolet light, which caused them to change their gait, demonstrating the mycelium’s ability to respond to its environment. In the third scenario, the researchers were able to completely ignore the mycelium’s native signal.

The implications extend far beyond the fields of robotics and fungi.

“This kind of project is not just about controlling a robot,” Mishra said. “It’s also about creating a real connection with the living system. Because once you hear the signal, you also understand what’s happening. That signal could be from some kind of stress. So you see the physical response, because these signals are not visualizable, but the robot visualizes them.”

Co-authors include Johnson, Hodge, Jaeseok Kim of the University of Florence, Italy, and undergraduate research assistant Hannah Baghdadi.