The way Cheerios stick together has inspired a new kind of robot.

The same phenomenon that causes beetles to float across a pond and Cheerios to swarm You can make little floating robots by putting them together in a cereal bowl.

One of them, the Marangoni effect, occurs when a fluid with low surface tension spreads rapidly across the surface of a fluid with high surface tension. This effect is exploited by: Sthenus A beetle that has evolved to move quickly across a pond by secreting a substance called stenusin and a toy boat that runs on soap.

To investigate how engineers can use it: jackson wilt Harvard University and his colleagues 3D printed round plastic pucks about 1 cm in diameter. Inside each was an air chamber for buoyancy and a small fuel tank containing 10 to 50 percent alcohol, which has a lower surface tension than water. The alcohol gradually leaks out of the puck and is propelled across the surface of the water.

The team used alcohol as fuel because, unlike soap, which eventually contaminates water and impairs the Marangoni effect, alcohol evaporates. It turns out that the stronger the alcohol, the better the results. “The beer would be pretty bad,” says Wilt. “Vodka is probably the best thing you can use. absinthe… “You must have tremendous momentum.” At top speed, the robot moved at a speed of 6 centimeters per second, and some experiments showed that the puck was propelled for 500 seconds.

By printing pucks with two or more fuel outlets and gluing them together, researchers can even create larger devices that trace broad curves or rotate in place. Using multiple pucks allows researchers to investigate the “Cheerios effect,” which is when cereals or other similar floating objects cluster. This happens because the fluid forms a meniscus, or curved surface, and these surfaces are attracted to each other.

Wilt says 3D printed devices can be useful in education to help students intuitively grasp concepts related to surface tension, but they can also be applied to environmental or industrial processes if carefully designed to produce more complex and elegant behaviors. says:

For example, if there is a substance that needs to be dispersed throughout the environment that could serve as a suitable fuel, the robot can automatically spread it around. “Let’s say you have a body of water that needs to release some chemicals, and you want to distribute them more evenly, or you have a chemical process that needs to settle the material over time,” says Wilt. “I think there’s some really interesting behavior here.”