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Fingerprints go micro

Fingermarks are produced by contact transfer of sweat, other skin secretions, and compounds picked up from the environment onto surfaces touched by a person’s fingers.

Each person’s fingermarks have unique patterns that have been used for identification since the nineteenth century. By using modern technologies additional information can be collected about the molecular composition of fingermarks, allowing a detailed understanding of the impact that ageing has on fingermark viability for biometrics.

Dr Johan Gustafsson, Dr Taryn Guinan and Prof. Nico Voelcker at the University of South Australia (UniSA), as part of the ARC’s Centre of Excellence in Convergent Bio-Nano Science and Technology, are identifying the distributions of molecular fingermark constituents using imaging mass spectrometry (IMS). Here, the aim is to catalogue forensically relevant compounds, such as illicit drugs. Fortuitously, by combining IMS with scanning electron microscopy (SEM), it is possible to assess the impact of environmental conditions such as temperature on molecular and morphological changes during fingermark ageing.The researchers are now combining their existing IMS analyses with time-of-flight secondary ion mass spectrometry (ToF-SIMS) in the AMMRF at UniSA. This is allowing comprehensive mapping of small molecules across entire fingermarks and sub-micrometre mapping of defined regions. SEM and combinatorial IMS will drive in-depth understanding of key changes in fingermark structure during ageing, and how these are mirrored by changes in small-molecule abundance and distribution. Preliminary work has confirmed that significant changes can occur, in structure and electrolyte distribution, across ageing fingermarks.

Scanning electron micrograph of a fingermark ridge (left) and two TOF-SIMS ion maps showing the distribution of sodium (centre) and potassium (right) across the ridge.