The tips of our fingers aren’t the only places we carry a fingerprint. Chemical splodges on our skin create unique, but invisible, patterns. A new technique called molecular cartography maps these chemicals in 3D – it works on entire human bodies, but equally on plants, and on surfaces like this ATM keypad. Swabs from this man’s fingers and each of the keypad keys were analysed for traces of urocanate, a natural chemical which protects skin from UV damage. Chemicals are fleeting – they naturally decay, or rub away, but this chemical detective work paid off. There is a strong trace of urocanate on the fingertips (red), and a weaker trace on some of the keys (yellow and orange), allowing the man’s PIN to be worked out (8-0-1-7). Molecular cartography has a bright future in forensics, agriculture and medicine, where invisible bacterial traces could be followed to a source of infection.
Written by John Ankers
BPoD stands for Biomedical Picture of the Day. Managed by the MRC London Institute of Medical Sciences the website aims to engage everyone, young and old, in the wonders of biomedicine. Images are kindly provided for inclusion on this website through the generosity of scientists across the globe.