An interdisciplinary team of researchers at the University of California, Merced, created a material that shrinks when heated, a new way of enabling a material to move using light or low-energy heat, and also discovered why that happens – findings that are featured in a paper published on the prestigious journal Nature's Chemistry website.
The article, “Large Negative Thermal Expansion of a Polymer Driven by Sub-Molecular Conformational Change ,” published Oct. 20, details the results of work Professor Jennifer Lu  has conducted for more than five years, and the breakthroughs accomplished by Lu, Professors Christopher Viney  and Erin Johnson , graduate student Xingyuan “Alex” Shen and Professor Changchun Wang of Fu Dan University in Shanghai, China.
“Our mechanism is completely different,” Lu said. “This is a whole new field – there’s a lot of work that can come from this.”
“We are particularly proud of this group of investigators,” Vice Chancellor for Research Sam Traina said. “The work is novel and groundbreaking, but this is only the beginning. We expect this effort to not only produce more fundamental knowledge but also to lead to a number of important applications in the future.”
The work also led to the realization that the material – polymers or macromolecules – could fold and unfold like a collapsible wine rack with the use of infrared light, a much lower-energy and less-damaging trigger than the ultraviolet light often used to make such changes.
"I was particularly excited to see the combination of experiments and computational models to advance our understanding of this novel material,” said School of Natural Sciences Dean Juan Meza. “This is the wave of the future.”
While practical applications are far in the distance, the material has the potential for use in near-infrared controlled mechanics, such as a device like an artificial heart valve, or thermal sensors for anticloaking and harvesting thermal waste. The material is extremely durable, Viney said, having shown no signs of degradation over tens of thousands of folds and unfolds.
Johnson, with the School of Natural Sciences, develops theories to examine interactions within and between molecules, while Lu, with the School of Engineering, specializes in novel nanomaterial design, synthesis and characterization. Viney, with the School of Engineering, is a materials scientist who focuses on the structure and properties of polymers.
“He’s an amazing student – one of the best I’ve ever seen,” Viney said.
“I am so fortunate to have such a diligent student who loves science,” Lu said. “For example, he worked almost every day from 9:30 a.m. to 10 p.m. when he was here this summer. He even biked to campus during the Christmas break, every day, with a shoulder broken in a skiing accident.”
The paper, available now online, was submitted in the spring and had to undergo reviews before publication. That means the team has had time to continue working on the project, and make many more advancements that have yet to be revealed.
“This is a wonderful example of UC Merced’s signature strength in interdisciplinary research and graduate education,” School of Engineering Dean Daniel Hirleman said. “It is gratifying to see the growth in our high-impact research being recognized in high-impact journals.”
Even though recognition in a Nature journal is a big honor, Viney, Johnson and Lu aren’t resting on laurels – they plan to continue working to optimize the new material, remaining excited about the work and their group.
“It’s a great example of collaboration between engineering and chemistry and between theory and experiment,” Johnson said.