Electrospun core (PVA-ninhydrin)-sheath (PVP) fibrous film for multi-level feature visualization and quantitative analysis of latent fingerprints

Background The development of level 3 features in various latent fingerprints (LFPs) is pivotal to improving the matching accuracy of damaged fingerprints. Among the various LFP development methods, the traditional ninhydrin method is widely employed in forensic science. However, it exhibits two key limitations: first, it is only effective for developing eccrine LFPs; second, it can only reveal level 2 features. These constraints compromise the extraction efficiency and utility of the developed fingerprints, thereby restricting the method's applicable scenarios. Results We report the fabrication of core (polyvinyl alcohol ninhydrin (PVA-ninhydrin))-sheath (polyvinyl pyrrolidone (PVP)) fibrous films by using coaxial electrospinning technology for high-level development of various LFPs. The film achieves safe, fast and chemical visualization of eccrine, sebaceous and natural LFPs with levels 1–3 features, showing a better visualization effect than ninhydrin solution and PVA-Nin fibrous film. It may be attributed to high specific surface area of thin film with uniform distribution of ninhydrin in the PVA core for high proportion of active sites of amino acids, which enables the film to have strong sweat adsorption and spreading properties. It further allows a more thorough and complete reaction between ninhydrin and the amino acids in the fingerprint residues that enhances the contrast of the developed photos. The statistical analyses of sweat pore count, ridge width, and pore spacing show high consistency and accuracy. Significant This study developed the core (PVA-ninhydrin)-sheath (PVP) fibrous films to achieve safe, fast and chemical visualization of eccrine, sebaceous and natural LFPs with levels 1–3 features and accurate quantitative analysis of the developed eccrine one. Moreover, even the interspacing and angles between sweat pores can be derived from level 3 features of the developed fingerprints. These results lay a robust foundation for subsequent fingerprint identification and personal recognition.