Slashdot Mirror
Universal Surface Scanner Detected
mcgrew writes to tell us that scientists at the University of California, San Diego, have created a new system that can test any surface for just about anything. "Their idea uses a thin layer of metal drilled with nanoscale holes, laid onto the surface being tested. When the perforated plate is zapped with laser light, the surface plasmons that form emit light with a frequency related to the materials touching the plate. A sensitive light detector is needed to measure the frequency of light given off. The team says devices using this approach can be small and portable, will work on very low power, and could detect everything from explosives to bacteria. All that needs to be done now is build a system able to decode the light signatures."
No, you need to use the Preview feature.
For large sets, this will be our guide even unto death, for the LORD will work for each type of data it is applied to...
It's not about detecting frequency. It's about detecting the conversion of light energy to plasmon-polariton energy. This is typically done by monitoring the change of intensity somehow. The polarization work that I mentioned was a very interesting method of detecting this conversion, because only one polarization (p-polarization) will convert.
Plasmons are very sensitive to the localized index of refraction at a surface. To put it simply, you change the localized index of refraction by sticking something to the surface, like a chemical or a virus envelope protein or a bacteria. When something sticks, it changes the conversion efficiency of light.
However, ANYTHING sticking will change the conversion efficiency of light: the amount depends only on the relative index of refraction of the adsorbed material and it's thickness.
To have a chemical or biological sensor, you have to engineer receptors, so that only certain things stick to certain places. One of the nice things about this gadget is that it is an array sensor, so they can put numerous receptors down (e.g. one for hepatitis-c virus envelope protein in one spot, one for e-coli in another spot).