A nanotechnologist has created the world's smallest and most plentiful Smiley - a tiny face measuring a few billionths of a metre across, that is assembled from strands of DNA.
Fifty billion Smileys, each a thousand times smaller than the diameter of a human hair, can be made at a stroke under the technique pioneered by Paul Rothemund at the California Institute of Technology (Caltech).
DNA, the molecule that comprises living things, has long been known for its versatility as a microscopic building block.
The molecule can be "cut" using enzymes and reassembled using matching rungs in its double-helix structure. This theoretically opens the way to making DNA quantum computers and nano-level devices including injectable robots that can monitor the body's tissues for good health.
But, until now, nano-assembly has been a complex atom-by-atom procedure that is also costly, because it is carried out in a vacuum or at extremely coldly temperatures.
Rothemund, writing in today's issue of Nature, describes a far simpler and much cheaper process in which long, single strands of DNA can be folded back and forth to form a basic scaffold.
{{/usCountry}}Rothemund, writing in today's issue of Nature, describes a far simpler and much cheaper process in which long, single strands of DNA can be folded back and forth to form a basic scaffold.
{{/usCountry}}The basic structure is then supplemented by around 200 shorter strands, which both strengthen it and act rather like pixels in a computer or TV image, thus providing a shape that can bear a complex pattern.