What if refrigeration could begin with something as simple as bending a piece of metal?
Researchers at the University of Illinois Urbana-Champaign have taken a step toward that possibility by developing a solid-state cooling system that repeatedly bends nickel-titanium shape-memory alloy wires to absorb and reject heat. Led by mechanical science and engineering professor Nenad Miljkovic, the team combines this bending-driven elastocaloric effect with roller-based heat exchangers to create a compact and efficient refrigeration system — without relying on conventional refrigerants.
Elastocaloric cooling technology is a leading contender in the search for more environmentally friendly refrigeration and air conditioning, which together consume nearly 20% of the world’s electricity. It works by taking advantage of an unusual property of shape-memory alloys like nickel-titanium (a.k.a. nitinol or NiTi): they change temperature in response to mechanical loads.
Most state-of-the-art elastocaloric devices stretch or compress the alloys to trigger this temperature change, but this approach requires large actuators and heavy-duty supporting structures to handle the extreme forces required, resulting in bulky, heavy, and expensive machinery.
Miljkovic’s team has now demonstrated an elastocaloric chiller using a different approach: bend the material instead. The new device uses a small stepper motor to wind commercially available NiTi wires around rollers of different diameters, causing a temperature change in the wire in response to curvature-defined bending loads.
The rollers double as heat exchangers, according to doctoral student Tayfur Maruf. “The elastocaloric temperature change by itself is only part of the problem,” said Maruf. “For a practical cooling system, we also must move heat into and out of the material efficiently, keep the actuation architecture compact, and understand how much power the complete system requires. Bending and roller-based heat exchange allowed us to address those challenges together.”
This innovative architecture achieved a rare combination of efficiency and compactness that could open the door to new applications for elastocaloric cooling. Testing showed the machine could deliver 4.5 watts of cooling for every watt of input power, “placing it among the highest reported efficiencies” compared to similar elastocaloric devices. It also succeeded in packing more cooling power into a smaller volume than previously reported prototypes.
“These results illustrate the potential of this approach to address mobile and portable cooling applications that compression-based devices are too heavy to accommodate,” said contributing researcher Daniel Levick.
The study was conducted by researchers in The Grainger College of Engineering at Illinois in collaboration with elastocaloric cooling start-up Barrow Green, LLC, NASA Glenn Research Center, and Ames National Laboratory, and has been published in the Cell Press journal Device.
The online publication, “Bending-Driven Elastocaloric Cooling Enables Efficient High-Performance Solid-State Refrigeration,” can be found here.
Device (https://doi.org/10.1016/j.device.2026.101334)
Authors: Tayfur Rahman Maruf, Asif Ahmed, Daniel Levick, Adrianna Johnson, Francisco Pereda, Stefan Ioana, Darin Sharar, Glen S. Bigelow, Lucas Griffith, Agata Czernuszewicz, Julie Slaughter, and Nenad Miljkovic.
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Nenad Miljkovic is a Founder Professor and Head of the Department of Mechanical Science and Engineering, with additional appointments in the Department of Electrical and Computer Engineering and the Materials Research Laboratory. He leads the Energy Transport Research Lab at Illinois.
Daniel Levick is the CEO of Barrow Green, LLC.
Tayfur Rahman Maruf is a mechanical engineering PhD student in the lab of Nenad Miljkovic.
Asif Ahmed is a mechanical engineering PhD student in the lab of Nenad Miljkovic.