Snail robot excretes sticky mucus that helps it crawl up slopes

A mucus-excreting robot with a single large foot can effectively imitate the way snails crawl over surfaces – even steeply inclined ones.

“I always say that snails are like Michael Jackson to me. You don’t see how they move, but somehow gliding is happening,” said Saravana Prashanth Murali Babu at the University of Southern Denmark during a presentation at the American Physical Society’s March Meeting in Minneapolis, Minnesota, on 4 March.

Fascinated by the shelled molluscs, Saravana and his colleagues decided to build a version of a snail’s single large, soft foot and use it as the basis of a robot that moves like a snail.

During his presentation, Saravana explained that the team chose to build the foot from a soft material that could be inflated in segments by small pneumatic pumps. He says that while the chemical properties of snail mucus have previously been studied in detail, the way the snail’s foot moves had only been hypothesised based on biologists’ observations. These past studies proposed that different parts of a snail’s foot hit the ground, then detach from it before hitting it again, and they do so out of sync with each other. This creates a wave form across the foot that lets the snail glide forward on its mucus.

The researchers replicated this “pedal wave” motion in their experimental robot, which could also excrete mucus, and saw it successfully move forward and make turns without falling over. It even managed to move up steeply inclined surfaces in some experiments, says Saravana.

Although the bot is still at the experimental stage, Saravana hopes that it will become the first ever robot that propels itself like a snail. To make it more self-contained, the team is experimenting with putting the pumps in a snail-like shell on top of the robot. The shell – a slightly oversized plastic replica of a real snail shell – can also house electronics for remotely controlling the robot, and a syringe system for releasing mucus beneath the robotic foot, mimicking a real snail’s slimy trail.

The team’s final goal, however, is to make the robot’s inflatable foot even softer and more similar to real snails, whose bodies are mostly made of water. The researchers hope that a robot that successfully moves on mucus could inform the design of soft medical robots that could eventually move inside the human body where mucus is also abundant.