Duke University scientists have used the self-assembling properties of DNA to mass-produce nanometer-scale structures in the shape of a 4×4 grids, on which patterns of molecules can be specified. They said the achievement represents a step toward mass-producing electronic or optical circuits at a scale 10 times smaller than the smallest circuits now being manufactured. Instead of using silicon as the platform for tiny circuits, as is done in the current manufacturing technique of photolithography, the Duke researchers used DNA strands to create grids less than one ten-millionth of a meter square. The smallest features on these square DNA lattices are approximately five to 10 billionths of a meter (nanometers), according to the scientists, compared with about 65 nanometers in silicon circuits created using photolithography. The structure of the tiles created the molecular equivalent of puzzle pieces that would self-assemble only in a specific arrangement when mixed together, with the DNA loop loaded with a desired “cargo” molecule that would form the structure the researchers wished to create. In one experiment, the scientists specified 16 unique puzzle pieces that fit together as a 4×4 grid that formed a puzzle spelling the letter “D.” Because each piece would only match up with its predetermined neighbors, the scientists could mix together a trillion of each type of tile in one batch to generate a trillion 4×4 grids.