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

Synopsis: Acoustic Waves Direct Particles in Microchannels
Fluid Dynamics

Synopsis: Acoustic Waves Direct Particles in Microchannels

Acoustic waves guided by the channels of a microfluidic device can precisely manipulate microscopic particles suspended in the liquid flowing through the device. Read More »

Synopsis: How Hairy Tongues Help Bats Drink Nectar
Fluid Dynamics

Synopsis: How Hairy Tongues Help Bats Drink Nectar

Experiments and theory show that hairs on a bat’s tongue allow the animal to drink 10 times more nectar than it could if its tongue were smooth. Read More »

Viewpoint: Heaviest Element Has Unusual Shell Structure
Nuclear Physics

Viewpoint: Heaviest Element Has Unusual Shell Structure

Calculations of the structure in oganesson—the element with the highest atomic number—reveal a uniform, gas-like distribution of its electrons and nucleons. Read More »

More Articles