Electrochemical impedance spectroscopy: A deeper and quantitative insight into the fingermarks physical modifications over time

- Ageing of fingermarks is monitored by electrochemical impedance spectroscopy.
- The impedance spectra are affected by physical variations of fingermark with time.
- Spreading of the mark and roughness modifications affect the impedance values.
- Electrochemical parameters can be plotted to calculate the fingermark ageing curve.
- The mark and the substrate contributions to the impedance can be differentiated.

The present work is focused on a novel approach for the study and quantification of some of the physical changes to which a fingermark deposited on non-porous substrates is subjected as its ageing proceeds. Particularly, electrochemical impedance spectroscopy (EIS) technique has been applied for the first time in order to monitor the electrochemical behaviour of the system constituted by the fingermark residue and the underlying substrate. The impedance spectra proved to be significantly affected by the presence of the mark residue as well as by its ageing process. Opportune fitting operations performed on the experimental data allowed obtaining quantitative electrochemical parameters used to reach useful information on the fingermarks ageing mechanism as well as to calculate the fingermark ageing curves from which fundamental information could be potentially extrapolated.