Linker-mediated binding of DNA-grafted colloids: how competition affects phase behavior

DNA is a promising tool for programming the self-assembly of new materials: its interactions are chemically specific, tunable, and predictable. In principle, DNA can be grafted to colloids to favor the formation of a predetermined aperiodic structure. In this talk, I promote linker-mediated binding of DNA-coated colloids as an experimental system that could create these hundreds of specific interactions in practice. Here, DNA-coated particles interact through DNA linker strands dissolved in solution. Using optical microscopy, we study the melting transition of our linker system as a function of linker concentration, grafting density, and DNA sequences. We find a phase diagram different from that of directly hybridizing DNA-coated colloids, featuring a reentrant melting transition at high linker concentrations and a region of stable coexistence between solid and fluid. We also examine how the introduction of hundreds of competing linker strands might affect linker-mediated interactions and show that the system can accommodate many interacting linkers simultaneously. These results show the tunability and capacity of our linker-mediated system, and demonstrate how it might expand the design space for aperiodic and adaptive structures.