Self-propelled active sheet

A two dimensional, shape-changing sheet that moved in a reactant-filled fluid
Image 1

Image 2

Can you identify Image 1 and Image 2? any similarities ?
May be it’s more easy to identify the second one. Yes! Its the ‘magic carpet’ from the folk tale of Aladdin, One Thousand and One Nights. 

This magic carpet from the tale captured lots of imagination of young minds, not only for its ability to fly but also for its features, such as waving and altering its shape to serve its riders. These features also triggered the curious minds of researchers from the University of Pittsburgh.

The result is the study titled Designing self-propelled, chemically active sheets: Wrappers, flappers, and creepers published in the journal Science Advances. (DOI: 10.1126/sciadv.aav1745)

Lead author, Abhrajit Laskar, co-author, Oleg E. Shklyaev, and the Principal Investigator Anna C. Balazs, designed a two-dimensional, shape-changing sheet that moves autonomously in a reactant-filled fluid.

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.

Further, 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, en wrapping an object, making a flapping motion, and tumbling over obstacles on a surface.

Image 1: animation of the unwrapping of a catalse-coated flower-like sheet around a capsule. Black arrows indicate the directionality and magnitude of the flow field in the solution. Credit: Abhrajit Laskar

“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,”

Dr. Anna C. Balazs

“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,” Dr. Shklyaev said.

Dr. Laskar added that 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, as well as generate particular fluid flows to transport particles throughout the device.

Journal Reference:
Abhrajit Laskar, Oleg E. Shklyaev, Anna C. Balazs. Designing self-propelled, chemically active sheets: Wrappers, flappers, and creepers. Science Advances, 2018; 4 (12): eaav1745 DOI: 10.1126/sciadv.aav1745

SOURCE: University of Pittsburgh press release materials
Written by M R Raghul

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