Simultaneous Transfer and Imaging of Latent Fingerprints Enabled by Interfacial Separation of Polydopamine Thin Film.

Various approaches have been developed to visualize a latent fingerprint (LFP) for personal identification, but simultaneous transfer of a LFP for preservation has yet to be achieved. We herein report a novel strategy for simultaneous transfer and imaging of LFPs on a broad variety of substrates by using the interfacial separation of polydopamine (PDA) thin film, followed by electroless silver deposition. In this approach, a PDA thin film deposited on a polydimethylsiloxane (PDMS) flake is used to cover the substrate carrying LFPs and then gently peeled off. During this cover-separation process, PDA film is interfacially transferred from PDMS to the LFP ridges on the substrate in a spatially selective manner, leaving behind a complementary (negative) LFP pattern on the PDMS flake. Upon PDA-catalyzed electroless silver deposition, positive and negative LFP patterns are imaged on the original substrate and PDMS flake, respectively. This approach relies on the remarkably different adhesion energy of PDA on fingerprint sweat and PDMS and is applicable to fresh and aged LFPs on most nonporous substrates.