Harvard Develops “Intelligent” Liquid

“We show that we can use this fluid to endow intelligence into a simple robot.”

Smart Water

Harvard researchers have created what they’re characterizing as an “intelligent liquid” — or in more specific terms, a programmable fluid with a unique structure that allows it to radically alter its properties, in an intriguing development for the burgeoning field of metamaterials.

While the substance may not literally be “intelligent,” it is remarkably responsive. As detailed in a new study published in the journal Nature, the fluid, or “metafluid,” is designed to have programmable compressibility, optical behavior, and viscosity. In a first for metafluids, it can even transition between Newtonian and non-Newtonian states.

The researchers claim that the fluid could have a wide variety of applications, especially in robotics — but more on that later.

“We are just scratching the surface of what is possible with this new class of fluid,” study co-author Adel Djellouli, a physicist at Harvard’s John A. Paulson School of Engineering and Applied Sciences (SEAS) said in a statement about the work. “With this one platform, you could do so many different things in so many different fields.”

Structurally Sound

Metamaterials are artificially engineered materials with rare properties that are, in the researchers’ words, “determined by their structure rather than composition.”

Unlike other metamaterials, whose building blocks are traditionally “arranged in fixed positions within a lattice structure,” this latest creation is made of tiny rubber-like spheres suspended in an incompressible fluid, in this case silicon oil.

These spherical capsules are filled with air and, when subjected to enough pressure, will buckle. Collapsed, the capsules form a lens-like half-sphere. Leave them alone, and they retain their normal shape. This radically alters the fluid’s properties: for example, the under-pressure half-spheres can allow light to focus and pass through, while the full spheres can block it.

“Unlike solid metamaterials, metafluids have the unique ability to flow and adapt to the shape of their container,”co-author Katia Bertoldi, William and Ami Kuan Danoff Professor of Applied Mechanics at SEAS, said in the statement. “Our goal was to create a metafluid that not only possesses these remarkable attributes but also provides a platform for programmable viscosity, compressibility, and optical properties.”

Dynamically Fluid

In a promising demonstration, the researchers used their metamaterial as the hydraulic fluid in a robotic gripper. The test was seemingly simple: all the robot had to do was pick up fragile objects like a glass bottle and an egg without crushing them.

Thanks to the metafluid, the robot crushed it — the test, that is. The fluid automatically responded to different pressures of the various objects without extra programming or external control, something that a traditional hydraulic fluid like plain old water wouldn’t enable the gripper to do.

“We show that we can use this fluid to endow intelligence into a simple robot,” Djellouli said.

Still, this is just an early preview of its capabilities. Next up, the researchers want to test the metafluid’s acoustic and thermodynamic properties, which are common applications of metamaterials in general.

“The application space for these scalable, easy-to-produce metafluids is huge,” Bertoldi said.