Vision: Packaging changes color when content spoils

Professor Tobias Kraus of the Leibniz Institute for New Materials wins the acknowledged Liesegang Prize presented by the Colloid Society. The prize honors his research on particle-based materials. Kraus is investigating how the properties of nano-materials depend on their structure and how these can be altered.

The cheese packaging in the refrigerator glows red. Small particles in the plastic of the packaging indicate that the cheese is spoiled. Professor Tobias Kraus is working on this vision of the future and conducting research into nanoparticles that react to their environment or soften hard materials. The scientist at the Leibniz Institute for New Materials (INM) is investigating how the properties of nanomaterials depend on their structure and how this can be altered. He is Professor of Colloid and Interfacial Chemistry at Saarland University and Head of the Structure Formation Program at the INM.

Kraus develops active nanocomposites. In these, metallic nanoparticles can move freely and reorganize in response to external stimuli. “We are currently working on a nanocomposite in which we steer the movement of the nanoparticles via the temperature. As a result, the color of the material changes depending on the temperature. But there are also other stimuli that could change the color of the material. Our vision is, for example, food films that change their color due to high concentrations of vitamin C or certain toxins and thus indicate whether a food is still edible or already spoiled,” states the head of the Structure Formation Program Department, explaining future possible applications.

Hybrid inks form another focus of his work. They consist of metal nanoparticles coated with conductive polymers and water or other polar solvents. The inks are suitable for printing conductive structures, for example on thin polymer films or paper. No subsequent thermal or UV treatment is then required, while standard metal inks require sintering after inkjet printing in order to become conductive. In a cooperative project with the Paper Technology Foundation, Kraus uses the hybrid inks, for example, to print RFID antennas on cardboard.

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