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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."
it's not a tricorder. you need to lay the perforated metal sheet against the surface you want to scan with it.
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...
Actually "Star Trek tricorder invented" is what I had for a headline in the original submission, and it's what the blurb on New Scientist's page said.
Don't let anybody tell you ScuttleMonkey doesn't edit!
Free Martian Whores!
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).
This is clearly their intention. However, for a spectroscopic solution to work, they must have clear spectral features for their target species, they must have a laser that can cover all the possible frequencies of interest, and a detector that will detect all the relevant frequencies. So, if they combine a universal laser with a universal spectrometer, their universal surface sensor will be complete.
For some target materials, the problem of distinct and unique spectral features can be a big one. For things like bacteria, containing a multitude of molecules with similar spectral features but slightly different function, you end up with spectral soup. I believe that there are some spectral features that indicate that you have bacteria, and not some other generic background material, such as pollen. However, you then need to say that you have some nasty material, and not just the usual microbes that are everywhere. I don't know how you do that without chemical receptors. Finally, if the receptors rely on DNA, you need to do a bit of biochemistry to actually get to the DNA.
Explosives could work, since you're dealing with specific molecules. However, in many scenarios if you need to touch the sample you're too damn close.