Resonant cavity dielectric spectroscopy for quality assurance evaluations of secure documents
Mary Kombolias, Jan Obrzut, Yaw S. Obeng
Paper is a biphasic bio-composite material. The complexity of paper from a material science point of view is increased when it is manufactured for or used as a substrate in security printing products. However, most tests to evaluate such printing and graphic arts substrates are destructive and ex situ, resulting in a loss of information. Other tests may be non- destructive but may only provide visual assessments without any correlation to the chemical and physical properties of the substrate. There is a need to explore new metrologies which can interrogate security printing substrates in a non-destructive and contactless manner and yield data which corresponds to visual and physicochemical attributes. Resonant cavity dielectric spectroscopy provides a means to gather information on printing substrates derived from cellulose as well as those from synthetic polymers. In this paper, we provide four case studies demonstrating the broad utility of the resonant cavity dielectric spectroscopy technique in the analyses of unprinted substrates and surface modifications. The inherent forensic capabilities of this technique lend it well to further applications in secure document manufacturing.