Abstract. The vacuum vaporization technique is widely used to develop of visualized latent fingerprints on substrate surface for forensics investigation. In this study, we reported the first utilization of lawsone in the vacuum vaporization technique. The lawsone was sublimation in vacuum and showed the detected latent fingerprints on thermal papers. The method involves hanging the thermal paper samples 5, 10, 15 cm above a heating source with dispersed lawsone solids in a vacuum chamber. The optimized condition for lawsone sublimation are 50, 100, 150 mg with low-vacuum (0.1 mbar) and vaporizing temperature at 40-60°C. The sample fingerprints were left for 1, 3, 7 and 30 days before examination comparison between lawsone and fingerprint ink pad using an Automated Fingerprint Identification (AFIS). The resulted showed that using 100 mg lawsone sublimation on thermal paper at the range of 10 cm evidenced the clear, detectable minutiae which can be used for visualization and identification of latent prints without the background black staining known. Thus, this study might be interested application for developing latent fingerprints as a solvent free technique and non-hazardous materials.
IntroductionThe vacuum vaporization is a technique of thin-film deposition in which the metals were brought into the gas phase by thermal sublimation and deposited to the surface of substrate for a thin film. This process is widely used in the semiconductor, microelectronic and optical industries. Currently, this technique is applied for visualized latent fingerprints as known as Vacuum Metal Deposition (VMD) [1][2][3][4]. For example, gold was deposited on polyethylene substrates to develop fingerprints [5], copper and gold can deposit on the polymer banknotes to visualize latent fingerprints [6] and gold/Zinc VMD was also successful to visualized the fingerprints on fabrics [7]. Moreover, the organic chemicals were also succeeded to develop latent fingerprints instead of metals e.g. the use of solid ninhydrin used develop the latent fingerprints on porous surface [8]. Thus, the organic chemicals that can undergo thermal sublimation and visualization are of interest to study for the vacuum vaporization. Lawsone is a naphthoquinone natural products from the leaves of Lawsonia inermis has been used as a skin and hair dye as its reacts with amino acids of keratin. The lawsone solution can also react with latent fingerprint deposits on paper surfaces to show purple-brown impressions of ridge details which are also photo luminescent [9]. Detection of latent fingerprints on thermal paper is an