A new smart and responsive material can stiffen up like a worked-out muscle, say the Iowa State University engineers who developed it.
Stress a muscle and it gets stronger. Mechanically stress the rubbery material - say with a twist or a bend - and the material automatically stiffens by up to 300 percent, the engineers said. In lab tests, mechanical stresses transformed a flexible strip of the material into a hard composite that can support 50 times its own weight.
This new composite material doesn't need outside energy sources such as heat, light or electricity to change its properties. And it could be used in a variety of ways, including applications in medicine and industry.
The material is described in a paper recently published online by the scientific journal Materials Horizons. The lead authors are Martin Thuo and Michael Bartlett, Iowa State assistant professors of materials science and engineering. First authors are Boyce Chang and Ravi Tutika, Iowa State doctoral students in materials science and engineering. Chang is also a student associate of the U.S. Department of Energy's Ames Laboratory.
Iowa State startup funds for Thuo and Bartlett supported development of the new material. Thuo's Black & Veatch faculty fellowship also helped support the project.
Development of the material combined Thuo's expertise in micro-sized, liquid-metal particles with Bartlett's expertise in soft materials such as rubbers, plastics and gels.
It's a powerful combination.
The researchers found a simple, low-cost way to produce particles of undercooled metal - that's metal that remains liquid even below its melting temperature. The tiny particles (they're just 1 to 20 millionths of a meter across) are created by exposing droplets of melted metal to oxygen, creating an oxidation layer that coats the droplets and stops the liquid metal from turning solid. They also found ways to mix the liquid-metal particles with a rubbery elastomer material without breaking the particles.
When this hybrid material is subject to mechanical stresses - pushing, twisting, bending, squeezing - the liquid-metal particles break open. The liquid metal flows out of the oxide shell, fuses together and solidifies.
"You can squeeze these particles just like a balloon," Thuo said. "When they pop, that's what makes the metal flow and solidify."
The result, Bartlett said, is a "metal mesh that forms inside the material."
Thuo and Bartlett said the popping point can be tuned to make the liquid metal flow after varying amounts of mechanical stress. Tuning could involve changing the metal used, changing the particle sizes or changing the soft material.
In this case, the liquid-metal particles contain Field's metal, an alloy of bismuth, indium and tin. But Thuo said other metals will work, too.
"The idea is that no matter what metal you can get to undercool, you'll get the same behavior," he said.
The engineers say the new material could be used in medicine to support delicate tissues or in industry to protect valuable sensors. There could also be uses in soft and bio-inspired robotics or reconfigurable and wearable electronics. The Iowa State University Research Foundation is working to patent the material and it is available for licensing.
"A device with this material can flex up to a certain amount of load," Bartlett said. "But if you continue stressing it, the elastomer will stiffen and stop or slow down these forces."
And that, the engineers say, is how they're putting some muscle in their new smart material.
The research team
Additional co-authors of the Materials Horizons paper describing smart composites that change stiffness under mechanical stress are:
Joel Cutinho, a former Iowa State graduate student who now works for Nanolab Technologies; Stephanie Oyola-Reynoso, a former Iowa State graduate student who's now a postdoctoral research associate at Harvard University in Massachusetts; and Jiahao Chen, a former Iowa State graduate student who's now a postdoctoral research associate at Northwestern University in Illinois.
Read the paper
Mechanically triggered composite stiffness tuning through thermodynamic relaxation (ST3R), http://pubs.
Martin Thuo | EurekAlert!
Printing complex cellulose-based objects
27.03.2020 | ETH Zurich
A key development in the drive for energy-efficient electronics
24.03.2020 | University of Leeds
Together with their colleagues from the University of Würzburg, physicists from the group of Professor Alexander Szameit at the University of Rostock have devised a “funnel” for photons. Their discovery was recently published in the renowned journal Science and holds great promise for novel ultra-sensitive detectors as well as innovative applications in telecommunications and information processing.
The quantum-optical properties of light and its interaction with matter has fascinated the Rostock professor Alexander Szameit since College.
Researchers at the University of Zurich show that different stem cell populations are innervated in distinct ways. Innervation may therefore be crucial for proper tissue regeneration. They also demonstrate that cancer stem cells likewise establish contacts with nerves. Targeting tumour innervation could thus lead to new cancer therapies.
Stem cells can generate a variety of specific tissues and are increasingly used for clinical applications such as the replacement of bone or cartilage....
An international research team led by Kiel University develops an extremely porous material made of "white graphene" for new laser light applications
With a porosity of 99.99 %, it consists practically only of air, making it one of the lightest materials in the world: Aerobornitride is the name of the...
Researchers at Graz University of Technology have developed a framework by which wireless devices with different radio technologies will be able to communicate directly with each other.
Whether networked vehicles that warn of traffic jams in real time, household appliances that can be operated remotely, "wearables" that monitor physical...
Terahertz waves are becoming ever more important in science and technology. They enable us to unravel the properties of future materials, test the quality of...
26.03.2020 | Event News
23.03.2020 | Event News
03.03.2020 | Event News
27.03.2020 | Power and Electrical Engineering
27.03.2020 | Life Sciences
27.03.2020 | Life Sciences