Harvard scientists develop ‘intelligent’ liquid

Researchers at Harvard University have created a versatile and programmable metafluid that can change properties such as viscosity and optical clarity in response to pressure. This new class of fluids has potential applications in robotics, optical devices, and energy dissipation and represents an important advance in metamaterials technology. (Artist’s concept). Credit: SciTechDaily.com

Scientists have developed metafluids with programmable responses.

Scientists at Harvard’s John A. Paulson School of Engineering and Applied Sciences (SEAS) have developed a programmable fluid with adjustable springiness, optical properties, viscosity, and even the ability to transition between Newtonian and non-Newtonian fluids. We have developed Metafluid.

The first-of-its-kind metafluid uses a suspension of tiny elastomer spheres, 50 to 500 microns in size, that buckle under pressure, fundamentally changing the properties of the fluid. Metafluids have the potential to be used in everything from hydraulic actuators to robot programs, intelligent shock absorbers that can dissipate energy depending on the strength of the impact, and optical devices that can change from transparent to opaque.

This research Nature.

“We’ve only scratched the surface of what’s possible with this new class of fluids,” said Adele Gerouri, a research fellow in materials science and mechanical engineering at SEAS and lead author of the paper. Ta. “He has one platform that allows him to do so many different things in so many different areas.”

Metafluid vs. solid metamaterial

Metamaterials (artificially created materials whose properties are determined by their structure rather than their composition) have been widely used in a variety of applications for many years. But most of the materials are solids, such as the metalenses pioneered in the labs of Federico Capasso, Applied Physics Professor Robert L. Wallace, and SEAS Senior Research Fellow in Electrical Engineering Vinton Hayes.

Adjustable optics with Harvard logo displayed below metafluid. Credit: Harvard University SEAS

“Unlike solids, metamaterial“Metafluids have the unique ability to flow and adapt to the shape of the container,” said SEAS Professor of Applied Mechanics and lead author of the paper Katia Bertoldi, William Quan Danoff and Ami. Mr. and Mrs. Quan Danoff said. “Our goal was to create a metafluid that not only possesses these excellent properties, but also provides a platform for programmable viscosity, compressibility, and optical properties.”

The researchers used a scalable manufacturing technique developed in the lab of David A. Weitz, professor of physics and applied physics at SEAS, to fill the air and suspend it in silicone oil. We manufactured hundreds of thousands of these highly deformable spherical capsules. . As the pressure within the liquid increases, the capsule collapses, forming a lens-like hemisphere. When that pressure is removed, the capsule bursts back into its spherical shape.

Properties and applications of metafluids

This transition changes many of the liquid’s properties, such as viscosity and opacity. These properties can be tuned by changing the number, thickness, and size of capsules in the liquid.

The researchers demonstrated the programmability of liquids by loading the metafluid into a hydraulic robotic gripper and having the gripper pick up glass bottles, eggs, and blueberries. Traditional hydraulic systems powered by simple air or water require some kind of sensing or external control to allow the robot to adjust its grip so he can lift all three objects without crushing them. is.

However, in the case of metafluids, sensing is not required. The liquid itself reacts to different pressures and changes its compliance to adjust the force of the gripper, allowing you to lift heavy bottles, delicate eggs and small blueberries without any additional programming.

“We showed that this liquid can be used to give intelligence to simple robots,” Geroli said.

The researchers also demonstrated a fluidic logic gate that can be reprogrammed by changing the metafluid.

Optical properties and fluid conditions

Metafluids also change their optical properties when exposed to changes in pressure.

When the capsule is round, it scatters light and makes the liquid opaque, just as air bubbles make aerated water appear white. But when pressure is applied and the capsule collapses, it acts like a microlens, focusing light and making the liquid transparent. These optical properties can be used in a variety of applications, including electronic inks that change color based on pressure.

The researchers also showed that when the capsule is spherical, the metafluid behaves like a Newtonian fluid, meaning its viscosity changes only in response to temperature. However, when the capsule collapses, the suspension transforms into a non-Newtonian fluid. This means that the viscosity changes depending on the shear force. The greater the shear force, the more fluid the suspension becomes. This is the first metafluid shown to transition between Newtonian and non-Newtonian states.

Next, the researchers aim to investigate the acoustic and thermodynamic properties of the metafluid.

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

Reference: “Programmable Metafluid Shell Buckling”, Adel Djellouli, Bert Van Raemdonck, Yang Wang, Yi Yang, Anthony Caillaud, David Weitz, Shmuel Rubinstein, Benjamin Gorissen, Katia Bertoldi, April 3, 2024 , Nature.
DOI: 10.1038/s41586-024-07163-z

The Harvard University Office of Technology Development is protecting intellectual property related to this research and exploring commercialization opportunities.

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