A UK company called Intelligent Fingerprinting has developed a new form of non-invasive drug screening: a handheld device that detects the breakdown products of commonly abused drugs in sweat released from pores in the fingertips.
An image of the fingerprint is taken to create a reference point and treated with a solution containing gold nanoparticles, which stick to the breakdown products of illicit substances. The particles are stained with a fluorescent dye and a second image of the print is taken.
This test is far quicker than alternative methods (it only takes about ten minutes) and it also provides proof that a positive result belongs to the owner of the fingerprint and is not down to sample contamination. Sweat is released from pores in the fingertips and eventually tracks along the fingerprint ridges, carrying with it traces of drug metabolites that gradually decrease in concentration. If the staining of the print is greatest at the pores, it provides solid evidence that the metabolites are being released from the sweat glands of the person being tested.