Ted Hueckel - Monolithic colloidal crystals made easy

Presentation by Dr. Ted Hueckel, from the Molecular Design Institute at New York University (NYU).

Abstract: Materials with complex microstructure have scope to usher in a new age of technology based on their exotic interactions with light. Of the numerous microfabrication techniques presently available, colloidal self-assembly has the highest potential to mass produce such metamaterials. However, there are still many challenges preventing particle dispersions from forming functional materials. Programming the interactions of colloidal building blocks is a major topic in soft matter and while several methods exist to chemically alter particles and induce attraction/assembly, they are like using superglue to stick LEGO bricks together — superfluous/messy. Here, we describe how the natural surface charge (+/-) of common colloidal particles can be harnessed for assembly, using coulombic attraction to grow ionic crystals. Stability is provided by commercial polymer, while electrostatic attraction is precisely tuned with salt to produce single crystals with millimeter dimensions. A growing library of crystal structures with well-defined habits are presented in high-resolution SEM images, owing to these products’ unique ability to harden into a robust state and be taken out of their solvent. Also discussed is the theoretical model backing this technique, as well as the computational efforts to simulate ionic crystal formation.