Taking a cue from nature, a global team of scientists has created a model of tiny robots that utilize sound waves to communicate and form massive swarms that behave intelligently. The researchers' findings were published in Physical Review X.
A new study led by Penn State researchers shows for the first time how sound waves could function as a means. Image Credit: Igor Aronson / Penn State
Acoustic signals have long been employed by creatures such as insects, whales, and bats for communication and navigation. According to team head Igor Aronson, Huck Chair Professor of Biomedical Engineering, Chemistry, and Mathematics at Penn State, the robot groups may eventually be able to execute complicated tasks, including cleaning up pollution, investigating disaster areas, or administering medical treatments from inside the body.
Picture swarms of bees or midges. They move, that creates sound, and the sound keeps them cohesive, many individuals acting as one.
Igor Aronson, Study Team Lead, Pennsylvania State University
The tiny, sound-broadcasting swarms of micromachines can move through confined places and even reorganize themselves if they get distorted, since they are self-organizing. According to Aronson, the collective intelligence of the swarms, also known as emergent intelligence, could one day be applied to carry out jobs like cleaning up pollutants in contaminated locations.
Beyond the surroundings, the robot swarms could operate within the body, for instance, delivering drugs straight to a trouble spot. According to Aronson, their capacity to “self-heal” means they can keep functioning as a collective unit even after disintegrating, which might be particularly helpful for threat detection and sensor applications. Their collective sensing also aids in detecting changes in their environment.
This represents a significant leap toward creating smarter, more resilient and, ultimately, more useful microrobots with minimal complexity that could tackle some of our world's toughest problems. The insights from this research are crucial for designing the next generation of microrobots, capable of performing complex tasks and responding to external cues in challenging environments.
Igor Aronson, Study Team Lead, Pennsylvania State University
The researchers created a computer model for the study that tracks the motions of tiny robots outfitted with a detector and an acoustic emitter. They discovered that, like a school of fish or a flock of birds, the individual robotic agents could collaborate easily through acoustic communication, changing their form and behavior in response to their surroundings.
The simulations saw the emergence of collective intelligence that would probably show up in any experimental study with the same design, according to Aronson, even though the robots in the paper were computational agents within a theoretical — or agent-based — model rather than actual manufactured devices.
“We never expected our models to show such a high level of cohesion and intelligence from such simple robots. These are very simple electronic circuits. Each robot can move along in some direction, has a motor, a tiny microphone, a speaker, and an oscillator. That’s it, but nonetheless, it’s capable of collective intelligence. It synchronizes its own oscillator to the frequency of the swarm’s acoustic field and migrates toward the strongest signal,” stated Aronson.
The finding represents a major milestone in the emerging field of active matter, which studies the collective behavior of self-propelled tiny biological and synthetic agents ranging from bacterial swarms to living cells to microrobots. Aronson noted that this is the first time sound waves have been used to drive micro-sized robots. Until now, active matter particles have been mostly regulated by chemical signaling.
“Acoustic waves work much better for communication than chemical signaling. Sound waves propagate faster and farther almost without loss of energy — and the design is much simpler. The robots effectively ‘hear’ and ‘find’ each other, leading to collective self-organization. Each element is very simple. The collective intelligence and functionality arise from minimal ingredients and simple acoustic communication,” added Aronson.
Alexander Ziepke, Ivan Maryshev, and Erwin Frey of the Ludwig Maximilian University of Munich are the other study authors. The John Templeton Foundation funded the research.
Tiny robots use sound to self organize
Video Credit: Pennsylvania State University
Journal Reference:
Ziepke, A., et al. (2025) Acoustic Signaling Enables Collective Perception and Control in Active Matter Systems. Physical Review X. doi.org/10.1103/m1hl-d18s