Researchers at Harvard SEAS Engineer ‘New Class of Fluids’

A group of researchers at Harvard’s School of Engineering and Applied Sciences engineered metafluids – the first of a “new class of fluids” — which bring a number of intriguing properties, such as tunable compressibility, changeable optical properties, and the ability to be programmed to handle a variety of loads.

The first author of the paper, Adel Djellouli — a research associate at SEAS — said the project “started with a coffee with a colleague of mine, Ben Gorissen.”

Over the next four years, Djellouli encountered many challenges, such as attempting to miniaturize the system.

“I failed completely, because this is not my bread and butter,” he said.

Physics professor David A. Weitz, a co-author of the study, credited Djellouli with having the “persistence and the drive to really make it happen to the scale that he did.”

The metafluids are composed of small spherical capsules filled with air and suspended in silicon oil, which are collapsible in response to pressure.

Weitz’s lab assisted Djellouli by developing a “highly scalable fabrication technique” that created the spherical shells on a smaller scale, making them “more like a fluid.” Weitz explained that while he thought the larger scales were “enough” to show the “basic physics,” Djellouli was “determined to make a smaller system.”

“Metamaterials are artificial materials that derive the properties from the structure, rather than the molecular composition,” Djellouli said, likening the metamaterials to Lego pieces stacked together.

While previous research in the field was mostly focused on solid materials, this research provides “tunable compressibility”, allowing uses that draw on the properties of both liquids and gasses.

Djellouli also noted the importance of the “optical tunability,” saying that metafluids can “go from opaque to transparent.”

“You have the ability to switch from Newtonian behavior to non-Newtonian behavior with pressure,” Djellouli said of the nature of metafluids, “which — to my knowledge — is unprecedented.”

These fluids can be used in robots and hydraulic cylinders, which help operate machinery such as cranes and excavators.

Djellouli said metafluids can be applied to technologies like excavators that currently use oil and have difficulty calibrating to a variety of load sizes. The metafluids could be “programmed to handle certain scenarios,” making it easier to operate the machinery.

“This is just scratching the surface of what we know about it,” Djellouli said.

“It’s something that just started from a coffee discussion, so I advise people to talk to each other and share ideas,” he added, “If you really believe in your idea, you should go for it.”