A bioinspired folding approach to assemble complex colloidal matter

When building blocks can move and stick to each other, they can self-assemble into new materials with exotic mechanical or optical properties. Researchers orchestrate colloidal self-assembly through careful design of an individual building block's geometry and interactions. The blocks assemble piece-by-piece, like a jigsaw puzzle that assembles itself. The problem with this approach is that the number of combinations is so vast that a unique structure requires that all particles be distinct. Instead, we fold a string of DNA-functionalized emulsion droplets into specific rigid geometries, analogous to how polypeptides fold into proteins. DNA-linked droplets are free to rearrange, allowing the system to reorganize and avoid kinetic traps. By imposing a hierarchy of interactions, we find that we can select structures with near-perfect yield even with basic interaction sequences. This non-equilibrium process allows for the selection of a desired state on the scale of minutes. This work presents an entirely new way to assemble colloidal structures and could be used to self-assemble mechanical or optical metamaterials.