Person: Rogers, William
Loading...
Email Address
AA Acceptance Date
Birth Date
Research Projects
Organizational Units
Job Title
Last Name
Rogers
First Name
William
Name
Rogers, William
5 results
Search Results
Now showing 1 - 5 of 5
Publication Programming colloidal phase transitions with DNA strand displacement(American Association for the Advancement of Science (AAAS), 2015) Rogers, William; Manoharan, VinothanDNA-grafted nanoparticles have been called “programmable atom-equivalents”: Like atoms, they form three-dimensional crystals, but unlike atoms, the particles themselves carry information (the sequences of the grafted strands) that can be used to “program” the equilibrium crystal structures. We show that the programmability of these colloids can be generalized to the full temperature-dependent phase diagram, not just the crystal structures themselves. We add information to the buffer in the form of soluble DNA strands designed to compete with the grafted strands through strand displacement. Using only two displacement reactions, we program phase behavior not found in atomic systems or other DNA-grafted colloids, including arbitrarily wide gas-solid coexistence, reentrant melting, and even reversible transitions between distinct crystal phases.Publication Using DNA to program the self-assembly of colloidal nanoparticles and microparticles(Springer Science and Business Media LLC, 2016-03) Rogers, William; Shih, William; Manoharan, VinothanGrafting DNA strands onto colloidal nano- and microparticles endows them with sequence-specific interactions. This Review explains how these interactions emerge from reactions between the strands and how the DNA sequences can add information that tells the particles how to self-assemble.Publication Photonic-crystal hydrogels with a rapidly tunable stop band and high reflectivity across the visible(The Optical Society, 2016-12-22) Park, Jin-Gyu; Rogers, William; Magkiriadou, Sofia; Kodger, Tom; Kim, Shin-Hyun; Manoharan, VinothanWe present a new type of hydrogel photonic crystal with a stop band that can be rapidly modulated across the entire visible spectrum. We make these materials by using a high-molecular-weight polymer to induce a depletion attraction between polystyrene-poly(N-isopropylacrylamide-co-bisacrylamide-co-acrylic acid) core-shell particles. The resulting crystals display a stop band at visible wavelengths that can be tuned with temperature at a rate of 60 nm/s, nearly three orders of magnitude faster than previous photonic-crystal hydrogels. Above a critical concentration of depleting agent, the crystals do not melt even at 40 degrees Celsius. As a result, the stop band can be modulated continuously from red (650 nm) to blue (450 nm), with nearly constant reflectivity throughout the visible spectrum. The unusual thermal stability is due to the polymer used as the depleting agent, which is too large to enter the hydrogel mesh and therefore induces a large osmotic pressure that holds the particles together. The fast response rate is due to the collective diffusion coefficient of our hydrogel shells, which is more than three orders of magnitude larger than that of conventional bulk hydrogels. Finally, the constant reflectivity from red (650 nm) to blue (450 nm) is due to the core-shell design of the particles, whose scattering is dominated by the polystyrene cores and not the hydrogel. These findings provide new insights into the design of responsive photonic crystals for display applications and tunable lasers.Publication Effects of Contact-Line Pinning on the Adsorption of Nonspherical Colloids at Liquid InterfacesWang, Anna; Rogers, William; Manoharan, VinothanThe effects of contact-line pinning are well known in macroscopic systems but are only just beginning to be explored at the microscale in colloidal suspensions. We use digital holography to capture the fast three-dimensional dynamics of micrometer-sized ellipsoids breaching an oil-water interface. We find that the particle angle varies approximately linearly with the height, in contrast to results from simulations based on the minimization of the interfacial energy. Using a simple model of the motion of the contact line, we show that the observed coupling between translational and rotational degrees of freedom is likely due to contact-line pinning. We conclude that the dynamics of colloidal particles adsorbing to a liquid interface are not determined by the minimization of interfacial energy and viscous dissipation alone; contact-line pinning dictates both the time scale and pathway to equilibrium.Publication Using DNA strand displacement to control interactions in DNA-grafted colloids(Royal Society of Chemistry (RSC), 2018) Gehrels, Emily; Rogers, William; Manoharan, VinothanGrafting DNA oligonucleotides to colloidal particles leads to specific, reversible interactions between those particles. However, the interaction strength varies steeply and monotonically with temperature, hindering the use of DNA-mediated interactions in self-assembly. We show how the dependence on temperature can be modified in a controlled way by incorporating DNA strand-displacement reactions. The method allows us to make multicomponent systems that can self-assemble over a wide range of temperatures, invert the dependence on temperature to design colloidal systems that melt upon cooling, controllably transition between structures with different compositions, or design systems with multiple melting transitions. This wide range of behaviors can be realized simply by adding a small number of DNA strands to the solution, making the approach modular and straightforward to implement. We conclude with practical considerations for designing systems of DNA-mediated colloidal interactions.