Inspired by the magic carpet featured in the folk tale of ‘Aladdin’, researchers have designed a two-dimensional, shape-changing sheet that moves autonomously in a reactant-filled fluid.
The ‘magic carpet’ in tales from “One Thousand and One Nights” to Disney’s “Aladdin” captures the imagination not only because it can fly, but because it can also wave, flap, and alter its shape to serve its riders.
“It’s long been a challenge in chemistry to create a non-living object that moves on its own within an environment, which in turn alters the object’s shape, allowing it to carry out brand new tasks, like trapping other objects,” said Anna C. Balazs from the University of Pittsburgh in the U.S.
Researchers previously have made chemically active patches on a surface that could generate fluid flow, but the flow didn’t influence the location or shape of the patch.
In the study published in the journal Science Advances, the team modelled spherical and rectangular particles that can move autonomously within a fluid-filled micro-chamber.
“Now we have this integrated system that utilises a chemical reaction to activate the fluid motion that simultaneously transports a flexible object and “sculpts” its shape, and it all happens autonomously,” Balazs said.
The group accomplished this feat of self-propulsion and reconfiguration by introducing a coating of catalysts on the flexible sheet, which is roughly the width of a human hair.
The addition of reactants to the surrounding fluid initiates both the carpet’s motion and the changes of its form.
“To best of our knowledge, this is the first time these catalytic chemical reactions have been applied to 2D sheets to generate flows that transform these sheets into mobile, 3D objects,” Balazs said.
By placing different catalysts on specific areas of the sheet and controlling the amount and type of reactants in the fluid, the group created a useful cascade of catalytic reactions where one catalyst breaks down an associated chemical, which then becomes a reactant for the next of the set of catalytic reactions.
Adding different reactants and designing appropriate configurations of the sheet allows for a variety of actions — in this study, enwrapping an object, making a flapping motion, and tumbling over obstacles on a surface.
“A microfluidic device that contains these active sheets can now perform vital functions, such as shuttling cargo, grabbing a soft, delicate object, or even creeping along to clean a surface,” said Oleg E. Shklyaev, a post-doctoral associate at the University of Pittsburgh.
“These flexible micro-machines simply convert chemical energy into spontaneous reconfiguration and movement, which enables them to accomplish a repertoire of useful jobs,” Shklyaev said.
If the sheet is cut into the shape of a four-petal flower and placed on the surface of a microfluidic device, the chemistry of the petals can be “programmed” to open and close individually, creating gates that perform logic operations, researchers said.
It can also generate particular fluid flows to transport particles throughout the device, they said.
