Researchers from University of California, San Diego and Tyco Electronics developed a sensor that can provide a visual signal when a gas mask is getting saturated and beginning to fail in filtering out chemicals. Using carbon fibers that absorb chemicals much like the activated charcoal in the filter, the sensor changes color as more organic pollutants are collected.
Sailor’s team assembled the nanofibers into repeating structures called photonic crystals that reflect specific wavelengths, or colors, of light. The wing scales of the Morpho butterfly, which give the insect its brilliant iridescent coloration, are natural examples of this kind of structure.
The sensors are an iridescent color too, rather than black like ordinary carbon. That color changes when the fibers absorb toxins – a visible indication of their capacity for absorbing additional chemicals.
The agency that certifies respirators in the U.S., the National Institute of Occupational Safety and Health, has long sought such a sensor but the design requirements for a tiny, sensitive, inexpensive device that requires little power, have proved difficult to meet.
The materials that the team fabricated are very thin – less than half the width of a human hair. Sailor’s group has previously placed similar photonic sensors on the tips of optical fibers less than a millimeter across and shown that they can be inserted into respirator cartridges. And the crystals are sensitive enough to detect chemicals such as toluene at concentrations as low as one part per million.
UCSD announcement: New Material Could Improve Safety for first Responders to Chemical Hazards…
Abstract in Advanced Materials: Carbon Nanofiber Photonic Crystals: Carbon and Carbon/Silicon Composites Templated in Rugate Filters for the Adsorption and Detection of Organic Vapors