By Mark Esposito, Guest Blogger
Scientists from Aristotle to his 21st Century successors have wondered how complex structures form in nature. Wim L. Noorduin, a postdoctoral fellow at the Harvard School of Engineering and Applied Sciences (SEAS) and lead author of a paper appearing on the cover of the May 17 issue of Science, may have the clues in his beaker. Manipulating chemical gradients in liquid have produced incredible flower-like structures based on the precipitation of crystalline forms on the microscopic level. Measured in microns, the crystal flowers (such as those pictured left) can be created by changing the chemical soup causing the crystals to grow towards or away from chemical gradients as the pH of the reaction shifts back and forth. Broad leaves, thin stems, or a rosettes of petals are all determined by the chemical reactions.
The work is important because changes in chemical gradients influence growth in nature: “delicately curved marine shells form from calcium carbonate under water, and gradients of signaling molecules in a human embryo help set up the plan for the body. Similarly, Harvard biologist Howard Berg has shown that bacteria living in colonies can sense and react to plumes of chemicals from one another, which causes them to grow, as a colony, into intricate geometric patterns.”
The flower making process involves dissolving common substances found in nature, a salt ( barium chloride) and waterglass (sodium silicate), into a beaker of water. CO2, already in the air, dissolves into the solution setting off a reaction. The crystals (known as barium carbonate crystals) form as the acidity level of the water around the crystals drop. As pH drops, the dissolved waterglass reacts to form a tiny layer of silica around the crystals which further drops the acidity and allows for the growth of the complex man-made “flowers.” To create broader leaved varieties, Noorduin adds more CO2. Reversing the pH gradient at the right moment can create curved, ruffled structures.
“You can really collaborate with the self-assembly process,” says Noorduin. “The precipitation happens spontaneously, but if you want to change something then you can just manipulate the conditions of the reaction and sculpt the forms while they’re growing.”
And even if the work at Harvard didn’t open windows into the creation of the natural world, bringing to life more flowers seems value enough. It was Monet who attributed his motivation for painting to the existence of flowers and Auguste Rodin, the father of modern sculpture, who said as poetically as he carved:
The artist is the confidant of nature, flowers carry on dialogues with him through the graceful bending of their stems and the harmoniously tinted nuances of their blossoms. Every flower has a cordial word which nature directs towards him.
Source: Science Daily
~Mark Esposito, Guest Blogger