Synopsis: Shape Shifting Water Droplets

Sheets of liquid droplets can spontaneously and reversibly change their shape.
Synopsis figure
T. Zhang et al., Phys. Rev. Lett. (2016)

Biological self-assembly—such as the folding of polypeptide chains into proteins—is the process by which smaller components spontaneously organize into ordered structures. Taking a cue from biology, researchers have engineered materials that, through self-assembly, fold into designated geometries. Recent work, for instance, showed that sheets of aqueous droplets can assemble into a variety of three-dimensional shapes. Expanding on this result, Mark Bowick and collaborators at Syracuse University, New York, have now demonstrated theoretically that such droplet networks can be programmed to reversibly switch between different shapes. This finding is a step toward biologically inspired robots that can change their shape according to their environment.

Bowick and his colleagues modeled sheets of micrometer-sized water droplets joined by permeable single lipid bilayers to form a tissue-like structure. By varying the concentrations of solutes within the droplets, the researchers created osmotic pressure that, by swelling some of the droplets and shrinking others, can cause the sheets to fold into several possible structures. The researchers focused on a configuration investigated in previous experiments—a four-petal design that spontaneously folded to produce a hollow sphere. They then demonstrated that they could reverse the shape change by placing the hollow sphere in a liquid medium with a higher solute concentration. According to their calculations, the droplets in the sphere lost water and shrank, leading the sphere to unfold back into the flat four-petal shape.

This research is published in Physical Review Letters.

–Katherine Kornei


Features

More Features »

Announcements

More Announcements »

Subject Areas

Chemical PhysicsFluid Dynamics

Previous Synopsis

Next Synopsis

Particles and Fields

The Heavy Limit of Dark Matter

Read More »

Related Articles

Focus: More Energy from Ocean Waves
Energy Research

Focus: More Energy from Ocean Waves

A new structure concentrates water wave motion and could lead to improved techniques for harvesting this renewable energy resource. Read More »

Synopsis: Levitating in a Fluid
Fluid Dynamics

Synopsis: Levitating in a Fluid

Researchers have identified a regime in which a magnetic stir bar can be made to levitate while it spins in a fluid. ­­ Read More »

Focus: Fluid Flow through T-Junction Traps More Particles than Expected
Fluid Dynamics

Focus: Fluid Flow through T-Junction Traps More Particles than Expected

Computer modeling shows that surprisingly large regions can trap particles carried by a fluid that is moving steadily through a pipe junction. Read More »

More Articles