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October 25, 2024
2 min read
This Is Your Robot Brain on Mushrooms
New rolling, hopping robots navigate via fungus
The fungal network hidden under fleshy, white king oyster mushrooms doesn’t just sprout elegant appetizers. It can also serve as a keen robotic sensor, helping to pilot a wheeled bot and a squishy, star-shaped hopping one.
Oyster mushrooms’ rootlike mycelial threads generate voltage spikes when flashed with ultraviolet light. In an experiment for Science Robotics, researchers used this process to direct fungal tendrils, grown in a petri dish, to activate robots’ motors via attached electrodes.
These bots join a family of machines known as biohybrids. Successes so far range from a silicone-based jellyfish that uses cardiac cells to propel itself in water to a two-legged robot powered by laboratory-grown skeletal muscle. Most of these efforts use animal tissue in place of mechanical motors; the new study uses a radically different organism’s superpowers and thus expands engineers’ toolboxes, says Rashid Bashir, a biohybrid researcher at the University of Illinois Urbana-Champaign, who was not involved with the new study.
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Fungi are inexpensive to maintain and excel at detecting subtle shifts—not only in light but also in nutrients and gases such as carbon dioxide and ammonia, says senior study author Robert F. Shepherd, an engineer at Cornell University. Shepherd dreams of agricultural uses for fungi-powered bots: machines that harvest ripe fruit, for instance, or add nitrogen to arid soil. His team began with light sensing for a simpler proof-of-concept experiment.
Translating a signal into motion for the rolling and starfish-shaped robots presented its own challenges. Beyond their electrical reaction to light, fungi produce a baseline current as they digest sugar; for the study, lead author Anand Kumar Mishra, also at Cornell, experimented with both minimizing and exploiting this extra information. In the latter case, robots reacted to all signals but moved faster in response to those prompted by UV light, which were larger. Mishra imagines that this model could come in handy for robots that might need to stop, slow down or switch directions in response to nitrogen-deficient pockets in agricultural fields.
In future work, Shepherd and Mishra hope to grow fungi throughout their robots so the devices can sense light or chemicals from every direction. If wired a particular way, the robots could also respond to these stimuli locally: fungus-controlled fruit pickers, for example, might extend multiple arms to the locations of different ripe peaches. The scientists will also investigate the longevity of the fungal tendrils.
For now Shepherd and Mishra are just glad that the proof-of-concept experiment succeeded. “We really had no idea where to start,” Mishra explains, “because these robots were the first of their kind.” It took the team three years to design one that could startle in response to UV light. Watching the mechanical starfish scamper across the table for the first time, Shepherd himself felt keenly “alive.”