The intersection of art and technology is a fascinating place, and researchers often use works of art to practice or demonstrate techniques that can have more practical applications later on. Researchers at the California Institute of Technology have recreated a miniature, monochromatic version of Vincent Van Gogh's The Starry Night, to test methods of precisely folding DNA and attaching fluorescent molecules, which can be applied to manufacturing smaller computer chips.
Although it's only the width of a dime, this isn't the smallest work of art we've seen. Last year, a Swiss team used quantum dots to print a picture measuring 80 x 115 microns, while researchers in Denmark laser-printed the Mona Lisa on a nanometer scale at around the same time. A team at Georgia Tech recreated the same painting using nanolithography techniques a few years earlier, while artist Jonty Hurwitz 3D-printed sculptures tiny enough to stand on an ant's head. Now Van Gogh has made his mark in the realm of pint-sized replicas, too.
Caltech created their Van Gogh using a technique called "DNA origami." Like its traditional papercraft namesake, the process involves folding strands of DNA into precise shapes, which can then play host to a range of microscopic components, such as carbon nanotubes, drugs or in this case, fluorescent molecules.
"Think of it a bit like the pegboards people use to organize tools in their garages, only in this case, the pegboard assembles itself from DNA strands and the tools likewise find their own positions," says Paul Rothemund, the Caltech professor credited with developing the technique. "It all happens in a test tube without human intervention, which is important because all of the parts are too small to manipulate efficiently, and we want to make billions of devices."
The tiny Starry Night represents about 10 years' worth of development and refinement of the process of DNA origami, and highlights its first practical application. The canvas for the artwork was a glassy material with a series of microscopic holes, known as photonic crystal cavities (PCCs). Using DNA origami, the team was able to position fluorescent molecules with extreme precision inside those cavities, to produce light of different intensities and form the picture. Rothemund likens to process to "using DNA origami to screw molecular light bulbs into microscopic lamps."
"Depending on the exact size and spacing of the holes, a particular wavelength of light reflects off the edge of the cavity and gets trapped inside," adds Ashwin Gopinath, the lead author of the study.
These PCCs were tuned to the wavelength of 660 nanometers, which gives the image its red color. If the molecules are tuned to resonate at the same wavelength, they'll glow, with a brightness determined by their position within the cavity.
Difficulties with controlling the number and position of the light emitters has held back previous attempts combining them with PCCs, but Gopinath overcame the issue by creating an array of over 65,000 cavities, each with several possible positions for the DNA origami to bind to, allowing a scale of eight different light intensities per cavity. Adjusting each one within a 256 x 256 grid of pixels, the team was able to recreate the famous painting.
As impressive as the achievement is, the fluorescent molecules have their limits, as they tend to burn out after around 45 seconds, and currently can only glow in shades of red. These issues will need to be tackled to open up more practical applications, such as optical computer systems in which large numbers of tiny light sources need to be integrated on a single chip.
The research was published in the journal Nature.