Scientists from Brigham Young University have been developing new “DNA origami” techniques to create complicated structures that were previously impossible. 
Using PCR amplification they were able to create strands of arbitrary length and to make multiple branching points, allowing them to write letters as seen in the picture on right.
From the abstract:
Designs for DNA origami have previously been limited by the size of the available single-stranded genomes for scaffolds. Here we present a straightforward method for the production of scaffold strands having various lengths, using polymerase chain reaction amplification followed by strand separation via streptavidin-coated magnetic beads. We have applied this approach in assembling several distinct DNA nanostructures that have thin (10 nm) features and branching points, making them potentially useful templates for nanowires in complex electronic circuitry.
Press release: Spelling B-Y-U with DNA…
Abstract in Nano Letters: Polymerase Chain Reaction Based Scaffold Preparation for the Production of Thin, Branched DNA Origami Nanostructures of Arbitrary Sizes