Fingerprint Imaging Enhancement by Deposition of Columnar Thin Films Nanostructures

Abstract

Imaging and visualization of latent fingerprints on smooth surfaces is not an easy task when the latent finger mark is on smooth and/or high reflecting surfaces. The surface where the fingerprint is located may present many physical and optical constraints, such as roughness, high background fluorescence which may be handled using time-resolved luminescence imaging (Mitchell and Menzel, Proc SPIE 1054:191–195, 1989; Alaoui et al., Forensic Sci Int 152:215–219, 2005). Optical techniques like oblique angle illumination and columnar-thin-film acquisition of fingerprint topology have been successfully used for visualization of fingermarks on smooth glass and mirror surfaces (Alaoui, Time-resolved luminescence imaging and applications. In: Byrnes (ed) Imaging for detection and identification. NATO security through science series. Springer, Netherlands, pp 243–248, 2007). We report preliminary results on the visualization of latent fingerprints on two smooth surfaces (glass and windows aluminum) using columnar thin films (CTF) nanostructures of CaF₂ followed by 1,2-indanedione fluorescence (Shaler, J Nanophotonics 5:051509, 2011). The preliminary results are promising. We have been able to visualize fingerprints on glass under dark field measurement after CTF deposition and observation under microscope (Dutta et al., Forensic Sci Int 228:32–37, 2013). Fingerprints on frame windows aluminum were able to be visualized after CTF deposition and 1,2-indanedione fluorescence. These results may open new options in fingerprint visualization and detection using columnar thin films followed by fluorescent reagents. Our preliminary results show that this technique can be useful for latent fingerprints on nonporous surfaces. More work is necessary to optimize the CTF deposition process and the chemical post treatment (solution concentration, temperature, humidity, etc.).