At the FAMU-FSU College of Engineering, a group of researchers has shone new light on molecules that tend to alter their shape in response to light.
William Oates, the Cummins Inc. Professor in Mechanical Engineering and chair of the Department of Mechanical Engineering at the FAMU-FSU College of Engineering. Image Credit: FAMU-FSU College of Engineering/Mark Wallheisier.
The team analyzed azobenzene-based polymers and discovered that their free volume — a measure of the space between polymer chains — was closely related to the potential of the polymers to convert visible light radiation into mechanical energy.
The findings of the study were published in the Advanced Functional Materials journal.
If you put a bunch of people in an elevator, it’s really hard to get out. But if you have enough space in between, you can move around. That’s what we found, that the space in between the mass of polymer molecules makes a difference.
Billy Oates, Study Senior Author and the Cummins Inc. Professor in Mechanical Engineering, FAMU-FSU College of Engineering
Azobenzene is known to be a photoswitchable chemical compound. This implies that electromagnetic radiation — specifically ultraviolet and visible light — has the tendency to change a molecule’s chemical properties and geometry.
A network of azobenzene polymers appears quite similar to a load of strings of spaghetti piled up together. When light shines on the network, it makes a few molecules shorter and altering their shape from a rod to a boomerang.
The photomechanical nature of azobenzene was examined by earlier studies but this study was the first to measure the bulk energy transformation for a system of azobenzene polymers at the molecular scale. Scientists have discovered that the light-to-mechanical energy conversion ratio became 10 times larger as the free volume rose from 0.5% to 12%.
In another phase of the study, the team also designed a new coarse-grained model to describe the interaction of the azobenzene polymers. The coarse-grained models help simplify the behavior of huge, complicated molecular systems with very little data loss. Therefore, researchers can execute simulations that would otherwise be impossible with intricate molecular models.
The study could pave the way for new smart materials technology. For instance, rather than making use of wires to move electricity, engineers could employ light to control machine components remotely. One viable application could be a technique to move the many mirrors that constitute an array at a solar-thermal power plant.
You don’t need to worry about messy electrical wiring. You just need a line of sight to get the light in the system. That’s the biggest opportunity here, the development of a new way to actuate materials and structures with light.
Billy Oates, Study Senior Author and the Cummins Inc. Professor in Mechanical Engineering, FAMU-FSU College of Engineering
Scientists from Shanghai Jiao Tong University, the University of Queensland and Cornell University were also part of this study.
This study was financially supported by the U.S. Department of Defense, as well as the Thousand Talent Young Scholar Program and the Oceanic Interdisciplinary Program from Shanghai Jiao Tong University (SL2020MS008).
Journal Reference:
Zhai, C., et al. (2021) Conformational Freedom-Enhanced Optomechanical Energy Conversion Efficiency in Bulk Azo-Polyimides. Advanced Functional Materials. doi.org/10.1002/adfm.202104414.