"Layer cake" chip detects cocaine
We're getting one step closer to a portable, practical and affordable "cocaine breathalyzer," thanks to research being conducted at the University at Buffalo. Scientists there have created a chip that detects the drug in samples of a person's blood, breath, urine or saliva.
Created by a team led by associate professor Qiaoqiang Gan (who recently brought us a new-and-improved solar still), the chip utilizes a process known as surface-enhanced Raman spectroscopy, and is described as being like an "optical layer cake."
On the bottom is a horizontal layer of silver, which acts as a mirror. Sitting on top of that is a layer of dielectric material such as silicon dioxide or aluminum oxide (a dielectric material is an insulator through which no electrical current can flow, but that does become electrically polarized when voltage is applied to it). Finally, on the very top is an "active layer" made up of light-trapping gold and silver nanoparticles.
The idea is that the chip would be built into a handheld device, which would start by extracting cocaine molecules from a provided biological sample. Those molecules – assuming there were any – would then get deposited on the surface of the chip, where they would fall between the nanoparticles.
When the chip is exposed to a laser light source, the mirror and the dielectric material manipulate the light, causing an increase in the number of photons at the active surface layer. This intensifies the manner in which the cocaine molecules scatter the light trapped by the nanoparticles. The handheld device would be able to analyze that distinct light-scattering signature, and determine if it matched the signature known to be produced by cocaine. It could conceivably also identify the unique light-scattering signatures of other drugs, such as marijuana.
"The high-performance chip we designed was able to detect cocaine within minutes in our experiments," says Gan. "It's also inexpensive. It can be produced using raw materials that cost around 10 cents, and the fabrication techniques we used are also low-cost."
A paper on the research was recently published in the journal Small Methods.
Source: University at Buffalo