All images credited to Wim L. Noorduin, Harvard University.
If you’re stuck inside on the Internet on a beautiful spring day, like us, please accept our condolences and this gallery of pictures of crystals induced to grow into beautiful, microscopic flowers. By manipulating the conditions where the crystals were forming, researchers were able to get the crystals to self-assemble as stems, leaves and buds, all on the tinest of scales.
Wim L. Noorduin, a postdoctoral fellow at the Harvard School of Engineering and Applied Sciences, and his colleagues dissolved barium chloride (a salt) and sodium silicate (also known as waterglass) into a beaker of water. Carbon dioxide from the air dissolved naturally into the water, fomenting a reaction to form barium carbonate crystals. In response to the crystals the pH of the solution surrounding them lowers, triggering a reaction with the dissolved waterglass, and adding a layer of silica to the growing structure. This reaction uses up acid from the solution and allows the barium carbonate crystals to continue to form.
As this process takes place, the shape the crystals take can be manipulated through changes to the solution–increases in carbon dioxide levels in the water creates “broad-leafed” structures. Reversing the pH gradient at the right moment can create curved, ruffled structures. "You can really collaborate with the self-assembly process," said Noorduin.
Noorduin and his team grew fields of the floral-looking crystals on glass slides, razor blades and even a penny they submerged in the solution. Then Noorduin took pictures of the crystals using an electron microscope to produce these false color images of the “flowers” after they assemble molecule by molecule. The black and white images aren’t quite as charming.
"When you look through the electron microscope, it really feels a bit like you’re diving in the ocean, seeing huge fields of coral and sponges," Noorduin said. "Sometimes I forget to take images because it's so nice to explore."’
Noorduin’s paper on the crystal manipulation is the May 17 issue of Science’s cover story.
Happy spring, anyway.