Soft robots – made from malleable materials – can get in and around thousands of places their hard counterparts can’t. But they are more difficult to manufacture.
A new technique called bubble molding could change things, according to a new article, published in Nature. This method uses “fancy balloons” that change shape in predictable ways when inflated.
Traditional robots have many uses, but they aren’t known for being gentle.
“They won’t be able to hold your hands and allow you to move somewhere without breaking your wrist,” says Professor Pierre-Thomas Brun, lead researcher of the study. “They are not naturally adapted to interact with soft things, like humans or tomatoes.”
Soft robots could be used to harvest produce, grab delicate items from a conveyor belt, or provide personal care to humans.
Developed by researchers at Princeton University in the United States, the new system involves injecting bubbles into a liquid polymer. Once the polymer has hardened, it can bend and move to grip objects.
The team uses bubble molding to develop and create hands that grab, clap fishtails, and slinky-like reels that can retrieve balls.
The researchers hope that this simple design could speed up the development of other soft robots.
Bubble molding uses fluid physics. The liquid polymer is an elastomer, which settles into a rubbery material similar to the outside of a ball. Using straws or spirals as a mold, air is pumped into the liquid polymer to create a bubble that floats upward as the polymer sets.
This film around the top of the bubble can then be inflated, wrapping around the hard bottom as it increases in size.
“If more time is allowed to drip before hardening, the film at the top will be thinner,” says first author Trevor Jones, a graduate student in chemical and biological engineering. “And the thinner the film, the more it will stretch when you inflate it and cause more overall flex.”
The researchers managed to mold star-shaped “hands” that delicately picked up a blueberry and even “fingers” that curl one by one, almost as if they were playing a piano.
“What’s really clever is this idea of shaping the structure solely by the natural movement of fluids,” says Professor François Gallaire, a professor of fluid dynamics at the École polytechnique fédérale de Lausanne, Switzerland, who n did not participate in the research.
“These processes are going to work at many different scales, including very small things. It’s exciting because casting these tubes with typical manufacturing methods could be very difficult, so there is the potential to make very small tubes.
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