The underappreciated role of nonspecific attractions in crystallization of DNA-coated colloids

DNA-coated colloids are ideal building blocks for studying self assembly due to the relative ease in programming chemically specific interactions between the constituent particles. The effective interactions that emerge are often modeled as having a short range attraction from DNA hybridization and a short range repulsion from the polymer and/or DNA brush on the surface of the particles. Furthermore, it is often assumed that these are the only relevant interactions that dictate the assembly of a wide variety of crystalline structures. In this talk, I will show that other non-specific attractive interactions do in fact alter the structure of DNA-programmed colloidal crystals and how changes in the particle synthesis can tune the strength of non-specific interactions. For example, I will show that the structure of an assembled crystal phase can be altered by adjusting the length of an inert polymer grafted to the particle surface, which we attribute to a competition between Van der Waals attraction and steric repulsion. This research indicates that the phase behavior of DNA-coated colloids is more complex than typically assumed and that nonspecific interactions can play a relevant role in determining the types of crystalline structures that form.