Tim A Savas | PubMed Health

PubMed2006

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. The top surface of the close-packed array, parallel to the substrate, shows a square symmetry, unlike the hexagonal symmetry seen in monolayers of spherical domains, which may provide a useful geometry for block copolymer lithography.

Crystallization↗

PubMed2005

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. Heating induces dehybridization between DNA strands, leaving the original pattern on the original surface and the copied pattern on the secondary substrate, and thus stamping (see Figure 1). Molecular recognition provides the unique and disruptive ability of transferring large amounts of information in a single printing cycle, that is the simultaneous stamping of spatial information (i.e., the patterns) and of chemical information (i.e., the features' DNA sequence--their chemical composition). This method combines high resolution (<40 nm) with the advantage of an exponential increase in the number of masters; in fact, any printed substrate can be reused as a master. Patterns fabricated via very different lithographic techniques can be replicated.

DNA↗