Quality of development of latent sebaceous fingerprints coated with thin films of different morphologies

Abstract

Interdependence between stress, preferred orientation, and surface morphology of nanocrystalline TiN thin films deposited by dual ion beam sputtering A new technique to develop a latent sebaceous fingerprint for visualization requires the macroscopically conformal deposition of a columnar thin film on top of the fingerprint. In order to correlate the thin-film morphology to the quality of development, dense thin films as well as films comprising either upright or tilted nanocolumns were deposited on multiple samples of the same fingerprint from a donor. According to an objective grading scheme, films with upright nanocolumns provided the best development while dense films provided the worst development.

Unusual Nature of Fingerprints and the Implications for Easy-to-Clean Coatings

“…6−8 In the case of the polymerization of cyanoacrylate (superglue fuming, as it is more generally known) to preserve latent fingerprints, the presence of water in the sebum and its role in the polymerization mechanism have been discussed. 7,9 Suffice it to say that the presence of water in the sebum has not been unambiguously demonstrated, 10,11 despite this potentially having a significant impact on the design of easy-to-clean surfaces.…”

“…Specifically, the spatial arrangement of macroscopic features within the ridge pattern of a fingerprint is employed as a tool to identify individuals . In order to image the fingerprint resting on a surface, a range of different chemical reactions between additives and the fingerprint residue are utilized to render the sebum material more robust and exhibit certain optical properties. − In the case of the polymerization of cyanoacrylate (superglue fuming, as it is more generally known) to preserve latent fingerprints, the presence of water in the sebum and its role in the polymerization mechanism have been discussed. , Suffice it to say that the presence of water in the sebum has not been unambiguously demonstrated, , despite this potentially having a significant impact on the design of easy-to-clean surfaces.…”

Vacuum-metal-deposition and columnar-thin-film techniques implemented in the same apparatus

“…If the platform is stationary, tilted nanocolumns form on the surface of the fingerprint residue. If the platform is rapidly rotated about an axis which passes normally through it, upright and parallel nanocolumns form [8,10] and the development quality is significantly better [11]. The bottom panel in Fig.…”

Visualization of partial bloody fingerprints on nonporous substrates using columnar thin films

“…During the deposition, the platform was continually rotated about its surface normal at 180 rpm. This rotation ensured the growth of upright columns [9,10,11] as opposed to tilted columns that would blur ridge detail [12] and reduce the postdevelopment quality [13]. CTF deposition rates were loosely controlled and allowed to vary between the bounds of »0.5 nm/s and »3 nm/s.…”