Three-dimensional self-assembly of spherical block copolymer domains into V-shaped grooves.

The self-assembly of a spherical-morphology block copolymer into V-shaped grooves has been investigated. Although spherical morphology block copolymers typically form a bcc sphere array in bulk, the V groove promotes the formation of a well-ordered fcc close-packed sphere array with the (111) planes of the array parallel to the groove walls. The sphere size in the block copolymer adjusts depending on the commensurability between the periodicity of the block copolymer and the film thickness within the V groove.

High resolution printing of DNA feature on poly(methyl methacrylate) substrates using supramolecular nano-stamping.

In recent years, a large number of devices based on organic and biological materials have been developed. To scale-up the production of these systems to industrially acceptable standards, there is a need to develop soft-material stamping approaches with the needed resolution, complexity, and versatility. We have recently developed a DNA-based stamping method (supramolecular nano-stamping, SuNS) that has superior resolution and can print multiple molecules at the same time.

Supramolecular nanostamping: using DNA as movable type.

Here we present a novel printing technique (that we call supramolecular nanostamping), based on the replication of single-stranded DNA features through a hybridization-contact-dehybridization cycle. On a surface containing features each made of single-stranded DNA molecules of known sequence, the complementary DNA molecules are hybridized, spontaneously assembling onto the original pattern due to sequence-specific interactions. These complementary DNA strands, on the end that is assembled far from the original surface, are 5' modified with chemical groups ("sticky ends") that can form bonds with a target surface that is brought into contact.

Diffraction of neutral helium clusters: evidence for "magic numbers".

The size distributions of neutral 4He clusters in cryogenic jet beams, analyzed by diffraction from a 100 nm period transmission grating, reveal magic numbers at N=10-11, 14, 22, 26-27, and 44 atoms. Whereas magic numbers in nuclei and clusters are attributed to enhanced stabilities, this is not expected for quantum fluid He clusters on the basis of numerous calculations. These magic numbers occur at threshold sizes for which the quantized excitations calculated with the diffusion Monte Carlo method are stabilized, thereby providing the first experimental confirmation for the energy levels of 4He clusters.