Visualization of latent fingerprints using a simple “silver imaging ink”

Fingerprints are unique characteristics of an individual; therefore, the imaging and recognition of latent fingerprints (LFPs) are a top-priority task in forensic science. Fast visualization of LFPs can greatly help policemen in screening potential criminal scenes and capturing fingerprint clues. Here, we developed a simple, rapid, easily performed method for nondestructive visualization of sebaceous LFPs using “silver imaging ink” as a new imaging moiety. In principle, when the ink dried at a proper temperature, in situ generation of dark silver nanoparticles on the fingerprint's furrow areas occurred and resulted in a negative image of the LFPs. Interestingly, the preparation of silver imaging ink and the visualization of LFPs were carried out in a short period time of no more than 10 min in total. Fingerprints on different nonporous surfaces and from different volunteers were detected successfully. Moreover, the level 2 and 3 substructures of the fingerprints could also be clearly identified. Thus, the present method opens a new avenue for LFP detection and will find wide-ranging applications in forensic investigations.