Harvard scientists have developed a “smart” liquid.

Scientists have created a meta-fluid with a programmable response.

John A. Scientists at Harvard’s Paulson School of Engineering and Applied Sciences (SEAS) have developed a programmable metafluidic fluid with the ability to control fine elasticity, optical properties, viscosity and even switch between Newtonian and non-Newtonian fluids.

The first type of metafluorescent liquid uses a suspension of tiny rubber balls – between 50 and 500 micrometers – that bend under pressure, radically changing the properties of the liquid. Metafluidics can be used in everything from hydraulic actuators to programmable robots to smart shock absorbers that can dissipate energy depending on the intensity of the impact to optical devices that can range from clear to opaque.

The study was published the nature.

“We’re only scratching the surface of what’s possible with this new class of fluids,” said Adele Zalouli, a research associate in materials science and mechanical engineering at SEAS and lead author of the paper. “You can do so many different things in so many different areas with this one platform.”

Metafluids vs solids

Metamaterials—engineered materials whose properties are determined by their composition rather than their composition—have been used in numerous applications over the years. But most materials – such as Federico Capasso and Robert L. Pioneering metallic minerals in Wallace’s lab, Fenton is a senior research associate in electrical engineering in the Hays School of Applied Sciences – solid.

Adjustable optics with Harvard University logo under metafluorescent liquid. Photo credit: Harvard University SEAS

“As opposed to solid Metamaterialian“Morphic fluids have a unique ability to flow and conform to the shape of their container,” said Katia Bertoldi, William and Amy Cowan Danoff, professor of applied mechanics in the College of Applied Sciences and senior author of the paper. “Our goal was to create a metafluid that offers not only these excellent properties, but also a platform for programmable viscosity, compressibility, and optical properties.”

Using highly scalable manufacturing technology developed in the laboratory of David A. The Weitz, Molinckrodt Professor of Physics and Applied Physics at SEAS, research team created several thousand of these highly deformed, air-filled spherical capsules and suspended them in silicone oil. . As the pressure in the liquid increases, the capsules collapse and form lens-like spheres. When this pressure is removed, the capsules return to their spherical shape.

Properties and Applications of Metafluids

This transformation changes various properties of the fluid, including viscosity and opacity. These properties can be adjusted by changing the number, thickness and volume of capsules in the liquid.

The researchers demonstrated the fluid’s programmability by loading a metaphysical fluid into a hydraulic robotic gripper and having the gripper pick up a bottle, an egg, and a berry. In a typical traditional air- or water-powered hydraulic system, the robot would need some sort of external sensor or controller to adjust its grip and pick three objects without crushing them.

However, with Metafluid there is no need for perception. The liquid itself responds to different pressures and changes the adjustment to adjust the strength of the handle to accommodate a heavy bottle, a delicate egg and a small berry without additional programming.

“We showed that we can use this fluid to give intelligence to a simple robot,” Jalouli said.

The team also demonstrated a fluidic logic gate that can be reprogrammed by changing the metafluidics.

Optical properties and liquid state

Metafluids also change their optical properties when exposed to different pressures.

When the capsules are spherical, they scatter light and make the liquid opaque, just as air bubbles make carbonated water appear white. However, when pressure is applied and the capsules break, they act like tiny lenses, concentrating light and making the liquid transparent. These optical properties can be used for a number of applications, such as electronic ink that changes color depending on the print.

The researchers also showed that for spherical capsules, the metafluid behaves like a Newtonian fluid, meaning its viscosity changes in response to temperature. However, when the capsules break, the suspension becomes a non-Newtonian fluid, meaning that its viscosity changes in response to shear force – the higher the shear force, the more fluid it is. It is the first metafluid to demonstrate transition between Newtonian and non-Newtonian states.

Next, the researchers want to explore the acoustic and thermodynamic properties of the superfluid.

“The scope of applications for these scalable, easy-to-produce metafluids is enormous,” said Bertoldi.

Reference: “Shell Indentation for Programmable Metafluids” by Adele Zalouli, Bert van Remdonck, Yang Wang, Yi Yang, Anthony Callaud, David Weitz, Shmuel Rubinstein, Benjamin Goersen, and Katja Bartoldi, 3 April 2024, the nature.
doi:10.1038/s41586-024-07163-z

Harvard University’s Office of Technology Development has protected the intellectual property associated with this research and is currently exploring commercialization options.

This research was supported in part by the NSF through grant number DMR-2011754 from the Harvard University Materials Research Science and Engineering Center.