Ben Rogers, PhD

Department of Physics
Brandeis University
(October 17, 2016)

Using DNA to Program Pathways in Complex Self-Assembly

What if a battery could stay charged for decades? What if medications could be delivered directly to diseased cells without harming healthy ones? Nanomaterials research is bringing these possibilities closer to reality. A nanomaterial has an internal structure similar to the same material on a larger scale, but has been genetically modified to exhibit different characteristics. Dr. Rogers discussed his work using modified DNA strands to design an altered self-assembly pathway for colloids (a non-crystallizing substance such as a gel). His work highlights how this altered DNA can lead to different behaviors and assembly phases as the colloid structure builds itself. This research could be useful for the nanotechnology goal of creating devices that can respond or change structure on demand.

DNA is not just the stuff of our genetic code; it is also a means to build complex materials. Grafting DNA onto colloidal nano- and microparticles can, in principle, ‘program’ them with information that tells them exactly how to self-assemble. Recent advances in our understanding of how this information is compiled into specific interparticle attractions have enabled the assembly of crystal phases not found in ordinary colloids, and could be extended to the assembly of prescribed, nonperiodic structures. However, structure is just one piece of a more complicated story; in actuality, self-assembly describes a phase transition between a disordered state and an ordered state, or a pathway on a phase diagram. In this talk, I presented experiments showing that the information stored in DNA sequences can be used to design the entire self-assembly pathway, and not just its endpoint. Using grafted DNA strands to induce specific attractions between particles, and free DNA strands that compete to bind with the grafted ones, I showed that it is possible to create colloids with exotic phase behavior, such as arbitrarily wide gas-solid coexistence, re-entrant melting, and even reversible transitions between different solid phases. Going forward, this work could prove especially useful in nanomaterials research, where a central goal is to manufacture functional devices that can respond or reconfigure on demand.