Robotic Snail Is Making Big Waves

Ocean plastic pollution has become a major environmental issue, with far-reaching consequences. The scale of the problem is immense, with millions of tons of plastic entering the oceans each year. This plastic can range in size from large debris like bottles and bags to microscopic particles known as microplastics. Both large and small plastic debris can pose a serious threat to marine life and human health.

Larger plastic items can entangle marine animals, causing injuries or even death. However, the more insidious threat lies in the ingestion of plastics by marine organisms. As plastics break down into smaller fragments over time, they are often mistaken for food by marine species. From plankton to large fish, many creatures unwittingly consume these plastic particles. This ingestion not only harms the marine animals directly but also has cascading effects throughout the food chain.

Although attempts are being made to reduce plastic pollution in the oceans, these efforts are largely concentrated on collecting larger pieces of plastic debris. For example, massive initiatives such as ocean cleanup projects and international agreements are designed to remove visible plastic waste from the ocean surface. However, these initiatives may inadvertently overlook the pervasive issue of microplastics, which are more difficult to detect and remove due to their small size and widespread distribution.

The methods used to collect larger items, involving nets or conveyor belts, do not have the ability to extract microplastics from bodies of water. These particles can be filtered out of water with the help of pumps, but that requires a lot of energy, which makes them impractical for large-scale clean up operations. Confronted with this dilemma, a multi-institutional team led by researchers at Cornell University took inspiration from the Hawaiian apple snail.

These tiny creatures can very efficiently move through water and suck in small particles of food along the way. By designing a robot that operates using similar principles, the team proved that it is possible to pump water at a high flow rate using small amounts of energy.

The snail-like robot consists primarily of a helical spine that is enclosed in a flexible, accordion-like shell that was 3D-printed with a thermoplastic elastomer. A servo motor turns the spine, which causes the outer shell to undulate like the foot of an apple snail. When placed near the surface of a body of liquid, this motion generates waves that can be leveraged to control the flow of the liquid and produce a significant pumping force. A number of experiments conducted by the team revealed the optimal undulation speed for generating maximal fluid flow.

The prototype robot is permanently attached to a frame and unable to freely swim. Further, the motor and battery that is required for operation would cause it to sink as it is presently designed. Moreover, the robot has no integrated system for filtering microplastics, and it is impractically small to make any meaningful environmental impact. As such, the researchers have some additional work ahead of them before these robots can be put to use in the real world.

Moving forward, the team is planning to conduct more experiments to help them exploit the full potential of the robot’s unique mechanism. They hope that others will build on their work, and potentially uncover new possibilities in remote sensing and actuation within liquids.