A brand 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 will get stronger. Mechanically stress the rubbery material — say with a twist or a bend — and the material routinely stiffens by as much as 300 p.c, the engineers mentioned. In lab exams, mechanical stresses remodeled a versatile strip of the material into a tough composite that can assist 50 occasions its personal weight.
This new composite material does not want exterior power sources similar to warmth, mild or electrical energy to alter its properties. And it might be utilized in a wide range of methods, together with purposes in medication and trade.
The material is described in a paper just lately revealed on-line by the scientific journal Materials Horizons. The lead authors are Martin Thuo and Michael Bartlett, Iowa State assistant professors of supplies science and engineering. First authors are Boyce Chang and Ravi Tutika, Iowa State doctoral college students in supplies science and engineering. Chang can also be a pupil affiliate of the U.S. Department of Energy’s Ames Laboratory.
Iowa State startup funds for Thuo and Bartlett supported improvement of the brand new material. Thuo’s Black & Veatch school fellowship additionally helped assist the mission.
Development of the material mixed Thuo’s experience in micro-sized, liquid-metal particles with Bartlett’s experience in smooth supplies similar to rubbers, plastics and gels.
It’s a strong mixture.
The researchers discovered a easy, low-cost technique to produce particles of undercooled steel — that’s steel that stays liquid even under its melting temperature. The tiny particles (they’re simply 1 to 20 millionths of a meter throughout) are created by exposing droplets of melted steel to oxygen, creating an oxidation layer that coats the droplets and stops the liquid steel from turning stable. They additionally discovered methods to combine the liquid-metal particles with a rubbery elastomer material with out breaking the particles.
When this hybrid material is topic to mechanical stresses — pushing, twisting, bending, squeezing — the liquid-metal particles break open. The liquid steel flows out of the oxide shell, fuses collectively and solidifies.
“You can squeeze these particles just like a balloon,” Thuo mentioned. “When they pop, that’s what makes the metal flow and solidify.”
The consequence, Bartlett mentioned, is a “metal mesh that forms inside the material.”
Thuo and Bartlett mentioned the popping level will be tuned to make the liquid steel stream after various quantities of mechanical stress. Tuning might contain altering the steel used, altering the particle sizes or altering the smooth material.
In this case, the liquid-metal particles comprise Field’s steel, an alloy of bismuth, indium and tin. But Thuo mentioned different metals will work, too.
“The idea is that no matter what metal you can get to undercool, you’ll get the same behavior,” he mentioned.
The engineers say the brand new material might be utilized in medication to assist delicate tissues or in trade to guard worthwhile sensors. There may be makes use of in smooth and bio-inspired robotics or reconfigurable and wearable electronics. The Iowa State University Research Foundation is working to patent the material and it’s accessible for licensing.
“A device with this material can flex up to a certain amount of load,” Bartlett mentioned. “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 placing some muscle of their new smart material.