Shapeshifting materials: Using light to rearrange macroscopic structures

OIST researchers create self-assembling molecules which can be broken down by ultraviolet light to recombine into novel macroscopic shapes.

Traditional chemistry is immensely powerful when it comes to producing very diverse and very complex microscopic chemical molecules. But one thing out of reach is the synthesis of large structures up to the macroscopic scale, which would require tremendous amounts of chemicals as well as an elaborate and complicated technique. For this purpose, scientists rely instead on "self-assembling" molecules, compounds that can interact with other copies of themselves to spontaneously congregate into spheres, tubes or other desired shapes. Using this approach, researchers at the Okinawa Institute of Science and Technology Graduate University (OIST) now reports in Chemical Communications new self-assembling molecules that can transform into novel, exotic and previously unobserved shapes by simply using UV light to force them to rearrange differently into "metastable" states.

When designing self-assembly structures, scientists typically aim for the state of lowest energy -- or "ground state," in which the structure would be at its highest stability. Less stable shapes are usually dismissed as incorrect and undesirable. However, this "ground state" being very stable makes it arduous to break down the structure if you wish to alter its shape. In this research, OIST scientists inserted a weakness into their ground-state self-assembled structures, resulting in structures requiring only a small nudge to collapse. In this case, the nudge is the use of ultraviolet light to snip a specific bond between two atoms within the molecule, splitting the structure into smaller fragments. The fragments are then able to co-assemble into less stable -- called metastable -- but novel and exotic shapes.

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