The possibility of prescribing local interactions between nano- and microscopic components that direct them to assemble in a predictable fashion is a central goal of nanotechnology research. Coating colloidal particles with DNA is a promising strategy to make functional nanoscale materials, because the particles can be programmed to spontaneously self-assemble into complex, ordered structures. Here, we advance a new paradigm in which self-assembly of DNA-functionalized colloidal particles is programmed using linker oligonucleotides dispersed in solution. We find a phase diagram that is surprisingly rich compared to phase diagrams typical of other DNA-functionalized colloidal particles that interact by direct hybridization. Specifically, we note a re-entrant melting transition upon increasing linker concentration, and show that multiple linker species can be combined together to prescribe many interactions simultaneously. A new theory predicts the observed phase behavior quantitatively without any fitting parameters. We show that linker-mediated interactions direct the self-assembly of colloids into equilibrium crystal structures. Furthermore, we demonstrate how different linker sequences and concentrations produce different crystal lattices, whose symmetry and compositional order are encoded exclusively by the linker-mediated interactions. We also examine the phase behavior of asymmetric linkers, which bind more strongly to one colloidal species than the other. We find that asymmetry strongly influences the concentration dependence of the colloidal interactions, which we explain using a mean-field model. We also find evidence that asymmetric linkers might help to reduce kinetic bottlenecks to colloidal crystallization. Taken together, these experiments and models enable the programming of hundreds of specific interactions, while also expanding our fundamental understanding of the unique phase behaviors possible in colloidal suspensions. Linker-mediated self-assembly expands the design rules and, in conjunction with various other schemes reported in the literature, enables the assembly of fully-addressable, mesoscopic structures.
|Advisor:||Rogers, W. Benjamin|
|Commitee:||Baskaran, Aparna, Han, Grace G. D., Weeks, Eric R.|
|School Location:||United States -- Massachusetts|
|Source:||DAI-B 82/3(E), Dissertation Abstracts International|
|Subjects:||Physics, Biophysics, Statistical physics|
|Keywords:||Colloid, Colloidal Crystallization, DNA, Oligonucleotides, Phase Behavior, Self-Assembly|
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