Researchers at Harvard University have developed a metafluid whose elasticity can be programmed and can go from opaque to transparent, among other properties that open up a wide range of applications, according to a study published in the journal “Nature.”
Metamaterials are created artificially, their properties are determined by their structure, not their composition, most are solid and some have been used for years in various applications, EFE reports.
Metafluids have the unique ability to flow and adapt to the shape of their container, and the researchers’ goal was to create one that, in addition to having these characteristics, would provide a platform for programming viscosity, compressibility and optical properties, explains one of the authors of the study, Katia Bertoldi.
Its potential applications are very varied, from hydraulic actuators for programming robots to intelligent shock absorbers capable of dissipating energy depending on the intensity of the impact, or optical devices capable of changing from transparent to opaque.
“We are just scratching the surface of what is possible with this new class of fluids,” said first author Adel Djellouli of Harvard University.
This kind of smart liquid uses a suspension of tiny, air-filled, highly deformable elastomer spheres with a size of between 50 and 500 microns, which bend under pressure, radically changing their characteristics.
When the pressure inside the suspending liquid (silicone oil) increases, the capsules collapse, forming a lens-like hemisphere, and when the pressure is removed they return to their shape.
This transition modifies many of the properties of the liquid, such as its viscosity and opacity, which can be adjusted by modifying the number, thickness and size of the capsules in the liquid.
The researchers demonstrated the liquid’s programmability by loading the metafluid into a hydraulic robotic gripper and having it pick up a glass bottle, an egg, and a blueberry.
In a traditional hydraulic system powered by air or water, the robot would need some kind of external sensor or control to be able to adjust its grip and pick up the three objects without crushing them, but with the metafluid this is not necessary, since the liquid itself responds to different pressures.
“We have shown that we can use this liquid to make a simple robot intelligent,” Djellouli said in a Harvard University statement.
The metafluid also changes its optical properties when exposed to varying pressures. When the capsules are round, they scatter light and make the liquid opaque, but when pressure is applied and they collapse, they act as microlenses, making the liquid transparent.
The researchers also showed that when the capsules are spherical, the metafluid behaves like a Newtonian fluid, meaning its viscosity only changes in response to temperature.
When the capsules collapse, the suspension becomes a non-Newtonian fluid, meaning its viscosity changes in response to stress – the greater the stress, the more fluid it becomes.
The authors highlighted that this is the first metafluid to have demonstrated a transition between Newtonian and non-Newtonian states.
The next step the team wants to take is to explore the acoustic and thermodynamic properties of the new metafluid.
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2024-07-09 02:19:18
