Chiral Systems Made from DNA.

The very chemical structure of DNA that enables biological heredity and evolution has non-trivial implications for the self-organization of DNA molecules into larger assemblies and provides limitless opportunities for building functional nanostructures. This progress report discusses the natural organization of DNA into chiral structures and recent advances in creating synthetic chiral systems using DNA as a building material. How nucleic acid chirality naturally comes into play in a diverse array of situations is considered first, at length scales ranging from an individual nucleotide to entire chromosomes. Thereafter, chiral liquid crystal phases formed by dense DNA mixtures are discussed, including the ongoing efforts to understand their origins. The report then summarizes recent efforts directed toward building chiral structures, and other structures of complex topology, using the principle of DNA self-assembly. Discussed last are existing and proposed functional man-made nanostructures designed to either probe or harness DNA's chirality, from plasmonics and spintronics to biosensing.

Unusual imaging properties of superresolution microspheres.

We employ a self-assembly method to fabricate dielectric microsphere arrays that can be transferred to any desired positions. The arrays not only enable far-field, broad-band, high-speed, large-area, and wide-angle field of views but also achieve superresolution reaching λ/6.4. We also find that many proposed theories are insufficient to explain the imaging properties; including the achieved superresolution, effects of immersion, and unusual size-dependent magnification. The half-immersed microspheres certainly do not behave like any ordinary solid immersion lenses and new mechanisms must be incorporated to explain their unusual imaging properties.