A great paper from UK chemists in Chem Comm: when working with polymers of S2N2, Paul Kelly and colleagues at Loughborough University found that the reaction was initiated by fingerprints. When they exposed a material to the chemical, it revealed any latent (invisible) fingerprints with a very low detection limit.

Perhaps my favourite bit, though, is that they tried to initiate the reaction using starting points other than fingerprints; they found that tiny residues of inkjet ink would show up brown as they started the polymerisation. Again, the limit is so low that they could even highlight the ink residues on the envelope a document had previously been in. With a bit of Photoshopping you could actually tell what text had been printed on the document, without ever seeing the original. Nifty eh? Here’s a sample:

Ink highlighted from an envelope with new polymer detector

With a bit of Photoshop and a bit of imagination...

For more detailed info read the Chemical Technology story posted recently.