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What’s the best way to stay safe from air or water that’s been polluted? As this ScienCentral News video reports, one nanotechnologist says the smaller the detector, the better it can protect us.
Smart Glitter Nanotechnologists hope that their innovations will transform electronics, medicine and health care, reduce energy needs, and even keep the environment cleaner. Right now, the Environmental Protection Agency is supporting researchers whose work promises to help detect and reduce pollution. One of them is Michael Sailor, a chemist and materials scientist at the University of California, San Diego.
Sailor has developed what he calls "smart dust", tiny particles of silicon, used to make semi-conducting chips for computers. These silicon particles can sniff out pollutants, and then signal a warning by changing color that is visible to the naked eye. Sailor foresees his smart dust becoming part of very tiny sensors–or simply being painted on walls or applied directly to protective clothing.
To give bits of silicon sensing power, Sailor uses chemistry to give them an open, sponge-like porous structure. Then each particle’s nanoscale pores are designed to recognize and sop up molecules of certain pollutants or toxins or even particular viruses or bacteria like E. Coli. "The type of molecules we can detect really depends on what chemistry we put in," Sailor explains.
Sailor calls this a "nano disco ball": it's smart dust that has turned red because it has detected and glommed onto a drop of oil. image: Jamie R. Link, UCSD
The next step is to give each particle what Sailor describes as "the ability to tell the outside world, 'I’ve found something'" by visibly changing color. That requires more chemistry to give each particle the multilayered structure of photonic crystals. In nature, photonic cystals' layers reflect light to give some beetle shells, insect wings and gem stones their iridescence. "A photonic crystal is a lot like a soap bubble film," Sailor says. "A glass full of soap solution is transparent; ther'’s no color to it. But if you blow a bubble, the solution becomes a thin film full of iridescent colors. In a beetle shell, a series of layers of organic material produce iridescence. We mimic these layers in silicon." For example, a particle of smart dust may have one green side and one red. When the particle detects a drop of a toxin, the green side attaches to the drop and changes color, so that the red side flashes a warning.
Sailor thinks that environmental protection has a great deal to gain by working on the nanoscale. Smart dust could become part of very small sensors, inexpensive enough to be used in vast networks that would minimize the risk of panic caused by false alarms. "You could spread hundreds or thousands through the environment," Sailor says, "and if a couple of them stop working, no big deal."
Sailor thinks that environmental protection has a great deal to gain by working on the nanoscale. Smart dust could become part of very small sensors, inexpensive enough to be used in vast networks that would minimize the risk of panic caused by false alarms. "You could spread hundreds or thousands through the environment," Sailor says, "and if a couple of them stop working, no big deal."
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