Mustafa Bilgin

Investigation of a Hydrochromic Ink Used As a Safety Feature

Mustafa Bilgin and Johannes Backhaus, University of Wuppertal

Hydrochromic inks change its colour under the influence of water or moisture. This colour change process can become reversible or irreversible. Thus, the focus is on the irreversible colour change, which remains in the state after a shift. Moisture is monitored in several technical processes, in the paper or plastics industry and in printing companies.  Humidity that deviates from the norm can cause problems in technical processes and even lead to production breakdowns. Particularly in the case of electronic components, the humidity of the surrounding air should not be too humid (oxidation) or too dry (diffusion).

The aim of this research project is to develop a hydrochromic ink for piezoelectric inkjet printing that serves as a security feature. Characteristic properties such as viscosity, surface tension and color change behavior are analyzed. In addition, limit values are defined that provide information about the degree of contamination. The optical reading process of the hydrochromic colour fields is performed by a camera, which transforms the colour values into information about the degree of contamination.