SAN FRANCISCO, Nov. 10 -- Researchers have combined diatom with a version of inkjet printing and optical sensing to create a sensing device that may be up to 10 million times more sensitive than some other commonly used approaches.
"Some existing sensors can detect compounds at levels of one part per billion, which sounds pretty good, but for many purposes that's not good enough," said Alan Wang, an assistant professor of electrical engineering in the Oregon State University (OSU) College of Engineering.
As corresponding author on a study published in the journal Nanoscale, Wang and his colleagues combined advanced optics with a fluidic system to identify compounds. With most conventional systems of this type, fluids must flow over a surface, and this limits the transport of specific molecules you might want to identify.
"A natural, living type of phytoplankton that creates very precise, tiny structures," Wang explained, diatoms in his study act as natural "photonic crystals" that harness the forces of convection against diffusion to help accelerate and concentrate molecules in a space where photons from optical sensors can get trapped, interact with and identify the compound through optical signatures.
"When liquids are deposited on it with carefully controlled inkjet devices, the droplets evaporate quickly, but, in the process, carry the molecules of interest to the diatom surface. This is the key to increasing the sensitivity of the photonic measurements."
The technology, the researchers said, can quickly and accurately identify what compounds are present, and approximately how much, at low cost. In one demonstration, they tried to identify trinitrotoluene, or TNT, a chemical with very low volatility, meaning comparatively few molecules escape that could allow detection when it is built into an explosive device. It was one million more times sensitive at identifying TNT than other common approaches, Wang said.
Already patented, the "optofluidic" technology with enormous sensitivity might improve biomedical sensing of cancer biomarkers; be used for extraordinarily precise forensics work; save the lives of military personnel in combat situations; detect illegal drugs; or help tell whether organic food is really pesticide free or not.
