Remember Shrinky Dinks, the translucent sheets kids use to draw things, then shrink in the oven to create all kinds of tiny trinkets? Scientists have found a way to turn them into super-strong robotic grippers.
Shrinky Dinks are made of polysterene plastic, a polymer that “remembers” its original shape. After creating them, the manufacturer stretches them to a larger size at the factory so kids can easily draw on a big surface with markers or pencils. Then, when they’re done, kids heat them in the oven until about 217 degrees F. At that point, the polysterene plastic recovers its original, pre-stretched shape, magically shrinking right before the kids’ eyes.
A team of scientists from the Department of Chemical and Biological Engineering at North Carolina State University and the Department of Aerospace Engineering at Auburn University in Alabama have found a way to use those properties to create a gripper, a claw that can grasp objects. This type of gripper could be used for soft robotic applications, robots that are not made of metal and mechanical parts but rather flexible materials that are comparable to those found in living organisms.
The research—published May 1 in American Chemical Society’s journal Applied Polymer Materials—describes a method to turn thermoplastic polystyrene sheets into grippers. Soft grippers are typically made of hydrogels or elastomers, which require solvents or continuous pneumatic pressure to change shape, both of which have drawbacks. Solvents can damage the object that needs to be manipulated, and pneumatic pressure can be energy-intensive. This technology avoids those pitfalls, as it doesn’t require chemicals or power to operate. In fact, it doesn’t even require heat, like the Shrinky Dinks.
To make these grippers, the researchers use a black inkjet printer to draw different shapes onto the thermoplastic film, then cut them according to their design. Different designs result in different geometries, and each geometry is optimized to manipulate objects of a corresponding shape.
Then, they activated the Shrinky Dinks with light. The black ink concentrates the natural radiation in light, heating up the drawn part of the sheet, which in turn contracts that surface and makes the sheet move into the final shape of the gripper. The grippers are single-use only, however, which is good enough for disposable soft robots that can work biomedical applications, for example. The grippers can release the objects if you apply additional heat to the entire surface.
The most surprising thing, as you can see in the video above, is their strength. They can hold over 24,000 times their own mass for several minutes before they fail and 5,000 times their own mass for months. This is much stronger than hydrogel and elastomeric grippers, the research team claims. It’s wild to see something so light holding a steel screw thousands of times its weight with such ease.
The researchers say that engineers will be able to create any three-dimensional shape they want using this method, adapting the grip to any imaginable object. However, they don’t highlight specific applications in their research. I spoke with Professor Michael Dickey, one of the researchers, and he told me that they started the project out of creative curiosity, not to solve an specific problem. “I think it might be useful for hanging objects on a wall, connecting parts together temporarily, or packaging,” he said, “I think any real-world application would want to take advantage of the fact that these materials can ship flat for remote deployment, then make a strong grip to any object triggered by light.”