Shape

The Granulobot is a modular system that blurs the distinction between soft, modular, and swarm robotics.

A new robotic platform developed at the University of Chicago can adapt to its surroundings in real time for applications in unfamiliar environments.

The platform, dubbed the Granulobot, consists of many identical motorized units each a few centimeters in diameter. The units are embedded with a Wi-Fi microcontroller and sensors and use magnets to engage other units.

As its name suggests, the Granulobot is inspired by the physics of granular materials, which are large aggregates of particles that exhibit a range of complex behaviors. After water, these are the most ubiquitous material on the planet.

“Granular materials are unusual compared to most other materials in that they can change their properties dramatically, all the way from liquid-like to rigid. They can be flowing through your fingers or become rock hard,” explained Heinrich Jaeger, Sewell Avery Distinguished Service Professor at the University of Chicago. This change from a fluid material to one that is solid is called a jamming transition and is a feature unique to jamming-based robotics.

The most commonly used example to illustrate the nature of granular materials is wet sand, which can behave either as a solid or liquid. “We rely on this property to eventually form complex shapes with our hands,” added Jaeger, describing how sand is molded to build sandcastles.

The idea behind the project was that if a grain of sand could be motorized and interact with its neighbors autonomously there would be no need for the human hand to mold the shapes, explained Baudouin Saintyves, a postdoctoral researcher in Jaeger’s lab at the University of Chicago who developed the Granulobot.

The concept is best exemplified by an amoeba, which is able to change its shape by extending and retracting a temporary projection, or pseudopod. Similarly, the Granulobot has no identifiable top or bottom, front or back – no wheels or legs that are identifiable with a specific task. A conceptual departure from traditional robotics, the Granulobot instead moves by deforming its overall shape.

As Saintyves explained, existing modular robotics system generally cannot deform their interior. Instead, only the outer surface units move. This results in a slow, iterative reconfiguration process. With the Granulobot, the interior units can reconfigure as a soft material would when under stress. Additionally, the individual units can uncouple from their neighbors to create several smaller robots that can move independently and eventually recombine.

According to the team of researchers, which also includes Matthew Spenko, professor of mechanical and aerospace engineering at the Illinois Institute of Technology in Chicago, the Granulobot system blurs the distinction between soft, modular, and swarm robotics. What is particularly exciting, Jaeger said, is that the Granulobot also represents one of the first systems that is both a programmable material and a soft robot.

“Programmable matter started this whole business,” noted Jaeger, who has been working on earlier related projects with funding from the Defense Advanced Research Projects Agency (DARPA). As part of this, one of the premises was to develop a way to assemble materials such that they could be programmed to change their shape and function as a whole. The Granulobot is a first step toward achieving this autonomously and in real time. The eventual goal is to go beyond programming specific functions or types of locomotion and instead let the Granulobot decide how to move by itself.

Funding for this collaborative project between the University of Chicago and the Illinois Institute of Technology was provided by the National Science Foundation through grant EFMA – 1830939. Additional support came through the use of shared experimental facilities, provided by the University of Chicago’s Materials Research Science and Engineering Center, which is supported by the National Science Foundation through grant DMR-2104733.

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