Polymer films nanoimprinted with checkerboard patterns of square wells between 200 nm and 800 nm in width have been shown by Center researchers to align calamitic (rod-like) liquid
crystals vertically, horizontally or tilted depending on the depth/width ratio of the wells. The LCs prefer to orient parallel to the surface when the
polymer films are smooth but when the polymer is topographically patterned, post-doc Youngwoo Yi and collaborators have demonstrated that the preferred average orientation of the LC director depends on the pattern profile, the increasing elastic energy density as the wells become narrower eventually overcoming the surface anchoring of the polymer and changing the average orientation in cells from planar to homeotropic. Nanoimprinting, a technique in which a spin-coated monomer film is polymerized while pressing against a finely-patterned master mold, can be used to produce topographically-patterned surfaces rapidly and at low cost. Yi's experiments suggest that suitably topographically-patterned polymer films could be used to control the alignment of a variety of anisotropic soft matter in advanced electrooptic devices including liquid crystal displays, where alignment of the liquid crystal director is essential in controlling the optical properties of the pixels. This work was published in Y. Yi, G. Lombardo, N. Ashby, R. Barberi, J. E. Maclennan, and N. A. Clark, Phys. Rev. E 79, 041701 (2009).

Polarized light photomicrograph of a hybrid nematic cell with checkerboard patterns of different square well widths (200, 600, and 400 nm, from top to bottom) on one surface and an OTES SAM-coated glass slide as the other. The director orientation changes from homeotropic to planar as the well width increases. The white scale bar is 20 μm. The insets show a sketch of the director field in a homeotropic well and an AFM image of a checkerboard pattern of 400 nm square wells imprinted on a polymer replica.

This Center workshop brought together researchers from across the world working at the forefronts of materials science & optics to discuss the emerging uses of light for control of ordered soft materials and advances in the use of liquid crystals to control light. The LC2CAM program included tutorial lectures, professional development presentations, and poster sessions. The workshop was featured in Nature Photonics and in an ICAM news release. The complete workshop presentations are available on the web.

Liquid crystals that realign in response to DNA can reveal subtle sequence alterations, even a single base mutation. Center investigator Dan Schwartz.and doctoral student Andrew Price showed that nematic liquid crystals, which naturally align themselves perpendicular to the surface of a surfactant-coated glass slide, tilt slightly following the addition of short lengths of single stranded DNA. The addition of complementary strands of DNA - with a base sequence that would bind to the strands on the slide - triggers the tilted molecules to return to their perpendicular alignment. However, adding a non-complementary DNA strand - with a sequence that differs by just one base - causes no such response. These differing responses of the liquid crystals are easily observed in polarized light. The finding could lead to cheap, portable alternatives to current lab-based analytical detectors. This work was published in A. Price and D. Schwartz, Journal of the American Chemical Society 130, 8188-8194 (2008) and has recently been featured in Chemistry World.

The texture of a liquid crystal film to which single-stranded DNA has been added (a) changes progressively with the addition of complementary single-stranded DNA (b-d).

Two young scientists who performed graduate research in the Center have been selected by the International Liquid Crystal Society as winners of the prestigious 2008 Glenn Brown Prize: Loren Hough for his study of the B4 and dark conglomerate phases of banana liquid crystals (directed by Noel Clark), and Giuliano Zanchetta for his studies of a novel class of liquid crystal assemblies based on short-chain DNA (directed by Center collaborator Tommaso Bellini, of the University of Milan). Both laureates are currently pursuing post-doctoral research.

Center members and a team of collaborators have discovered some unexpected forms of liquid crystals of ultrashort DNA molecules immersed in water, providing a new scenario for a key step in the emergence of life on Earth. The research is described in a paper published in the Nov. 23 issue of Science (download Abstract or Full Text from Science). Read more in the Press Release.

Cool Chemistry wows audience at Pueblo Super Science Saturday (April 2007)

Cool and Creative Chemistry, an interactive K-12 outreach program designed by Center faculty and students, was presented to an enthusiastic audience of children and their parents as part of Super Science Saturday at the Steelworks Museum of Industry & Culture in Pueblo, Colorado. Read more in this news story.

Noel Clark elected to National Academy of Sciences (April 2007)

Center Director Noel Clark has been elected to the National Academy of Sciences. Read more in the press release.

21st International Liquid Crystal Conference
(July 2006)

The Center organized the 21st ILCC held in Keystone, in the Colorado Rockies, from 2-7 July 2006. See the ILCC2006 archive website.

Noel Clark wins 2006 Buckley Prize
(October 2005)

University of Colorado at Boulder physics Professor Noel Clark has won the American Physical Society's 2006 Oliver E. Buckley Prize for Condensed Matter Physics in recognition of his work in liquid crystals. Read more in the press release.