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Article---Hmmm
Posted: Tue Mar 24, 2009 9:19 am
by Charles Parker
Fluorescent fingerprints
23 Mar 2009 - Latent fingerprints at the scene of a crime can give vital clues in a criminal investigation. Giseop Kwak and colleagues from Kyungpook National University, in Korea, have successfully developed a technique to detect fingerprints in a convenient and non-destructive manner.
Kwak and colleagues use a highly fluorescent conjugated polymer film to detect fingerprints. All latent fingerprints contain oil residues, made up of triglycerides, wax esters and squalene, which are deposited when the fingerprint was made. On contact with the fluorescent polymer film, these residues diffuse into microvoids throughout the film resulting in film swelling and an increase in fluorescence intensity. High resolution images with clear ridges and valleys are obtained using this technique, which could help aid officers investigating crime scenes.
Significantly, the fluorescent conjugated polymer film is responsive to even slight amounts of oil residues, and therefore will be effective in spite of individual variations of quantity.
‘We expect the present polymer film to be a useful material for convenient, non-destructive fingerprint detection and highly reliable evidence accumulation in criminal investigations,’ says Kwak.
Original article: Kwak et. al.; "Fluorescence imaging of latent fingerprints on conjugated polymer films with large fractional free volume"; Chem. Commun. 2009
Now there is something new from the science world. All latent prints contain oil residues? And to think I was taught wrong and have been teaching it wrong all these years. Thanks to scientist for correcting my lack of knowledge.
And the non-destructive part-----hmmm---interesting in that the film sucks up the oil residue like a sponge but does not destroy the print on the substrate. Isn't science wonderful.
Boy where would we be without them to set us straight.
Re: Article---Hmmm
Posted: Wed Mar 25, 2009 7:10 am
by Gerald Clough
Charles Parker wrote: Isn't science wonderful.
Boy where would we be without them to set us straight.
Thank some anonymous editor at Chemical Communications. So far as I can see from a quick look through the article itself, the authors never claim all fingerprints have an oil component. They ran their experiment with impressions made by deliberately charging the finger with face oil and again without any charging. The article is at:
http://www.rsc.org/delivery/_ArticleLin ... ce_Article
Nice images. Another neat thing the abstract doesn't mention is that the film is reusable. They don't go into the mechanics of doing the transfer, but it looks (aside from the nature of the film itself) distinctly low-tech relative to a lot of other methods and so possibly a resource for less well endowed units. And I note their mention of the film being "hydrophobic," which among science guys means it repels water. A hydrophobic material may, for instance, be used to separate oil from water. And that makes me think about applications in wet environments.
I'm not yet prepared to give them a pass on "nondestructive." They don't include any attempt to do a second transfer or to subsequently develop by another method, and there's no detailed description of the film to give one any idea of how much matrix is transferred, so from the article I can tell if it's more or less destructive than, say, Gellifter.
Re: Article---Hmmm
Posted: Wed Mar 25, 2009 2:50 pm
by Charles Parker
Gerald----danged editors.
The short piece did not do the article justice----impressive---very impressive.
Matter of fact so much that I downloaded it.
Re-useable as well.
I think this one might have more promise than the spent casing processing of not so long ago.
Re: Article---Hmmm
Posted: Thu Mar 26, 2009 6:36 am
by Gerald Clough
Charles,
I asked Giseoop Kwak about the mechanics. He says it's very simple. The film seems to handle about like a wet piece of paper, so far as pliability and such. Just press the film to the surface for about ten seconds, and use some image processing. He sent me a couple of very short movies. One is them doing a lift transfer. The other is directly transfer from finger to film. They are shot by ALS lighting, and are just of the transfer. The surface transfer image isn't nearly so impressive as the images in the paper, but it's just a single event and may not represent the best unprocessed image. The direct transfer from a finger shows that the film can take a nice impression.
My immediate impression is that it's a lot like Gellifter in the way it transfers, although Gellifter does well on rough surfaces, and although they say the film does not, I think there's a lot of investigation possible with different backings. All they do in the movie is apply the film and rub it down like tape. I have a feeling that they may even be doing it wrong by rubbing it down and that a proper backing just pressed and held might be better. I'll see about coming up with a piece of this stuff. If I can, I'll get with you at your place and see what we can do.
I'll get the movies up someplace and come back with a link to them.