Shape memory in self-adapting colloidal crystals

• Published in: Nature (London) Vol. 610; no. 7933; pp. 674 - 679
• Main Authors: Lee, Seungkyu, Calcaterra, Heather A., Lee, Sangmin, Hadibrata, Wisnu, Lee, Byeongdu, Oh, EunBi, Aydin, Koray, Glotzer, Sharon C., Mirkin, Chad A.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group 27.10.2022
• Subjects: Broadband; Chemical bonds; Colloids; Compression; Crystal structure; Crystallinity; Crystals; Deformation; Deoxyribonucleic acid; DNA; Electrostatic properties; Energy conversion; Energy storage; Incident light; Inhomogeneity; MATERIALS SCIENCE; mechanical properties; Microscopy; Morphology; nanoparticles; nanostructures; Optical properties; organizing materials with DNA; Refractive index; Refractivity; Rehydration; Shape memory; Single crystals; Ultraviolet absorption; Values; Viscoelasticity; Wavelengths
• ISSN: 0028-0836; 1476-4687
• DOI: 10.1038/s41586-022-05232-9

Reconfigurable, mechanically responsive crystalline materials are central components in many sensing, soft robotic, and energy conversion and storage devices1-4. Crystalline materials can readily deform under various stimuli and the extent of recoverable deformation is highly dependent upon bond type1,2,5-10. Indeed, for structures held together via simple electrostatic interactions, minimal deformations are tolerated. By contrast, structures held together by molecular bonds can, in principle, sustain much larger deformations and more easily recover their original configurations. Here we study the deformation properties of well-faceted colloidal crystals engineered with DNA. These crystals are large in size (greater than 100 pm) and have a body-centred cubic (bcc) structure with a high viscoelastic volume fraction (of more than 97%). Therefore, they can be compressed into irregular shapes with wrinkles and creases, and, notably, these deformed crystals, upon rehydration, assume their initial well-formed crystalline morphology and internal nanoscale order within seconds. For most crystals, such compression and deformation would lead to permanent, irreversible damage. The substantial structural changes to the colloidal crystals are accompanied by notable and reversible optical property changes. For example, whereas the original and structurally recovered crystals exhibit near-perfect (over 98%) broadband absorption in the ultraviolet-visible region, the deformed crystals exhibit significantly increased reflection (up to 50% of incident light at certain wavelengths), mainly because of increases in their refractive index and inhomogeneity.