C. Lehmann¹, G. Bräuer¹, R. Bandorf², H. Gerdes², S. Körner², B. Szyszka³, A. Dietzel^1
1Technical University Braunschweig, Braunschweig, Germany
²2Fraunhofer Institute for Surface Engineering and Thin Films IST, Braunschweig, Germany
³Technical University Berlin, Berlin, Germany
The production of functional coatings on metal, glass, and polymer substrates through sputtering has been established on an industrial scale for 50 years. Porous or highly outgassing substrates such as paper or wood are generally considered incompatible with vacuum coating technologies. While there have been isolated studies on feasibility, systematic research results remain largely absent.
Paper is a natural, renewable raw material. The coating of tear-resistant paper in roll form is cost-effective and can significantly contribute to reducing plastic waste, thereby promoting sustainability. Potential applications for coated paper include:
• Sensors: Use in conductivity analyses in chemical process engineering and for paper-based multi-electrode arrays (MEAs) in biotechnological research.
• Electronics: Application as a dielectric in thin-film transistors (TFTs).
• Barrier coatings: Protection against moisture, oxygen, and other gases, e.g., for food packaging to extend shelf life.
• Hygienic applications: Antimicrobial silver coatings for wall coverings, medical packaging, or hygiene papers.
Various sputtering techniques from gas flow sputtering to HIPIMS (High Power Impulse Magnetron Sputtering) allow a broad variation of energy levels of film forming species. In a first study, two different paper types (7×3 cm²) were successfully coated with silver, titanium and titania in a short cycle system using DC sputtering at target power densities up to 7,7 W/cm².
Structural investigations by Environmental Scanning Electron Microscopy (ESEM) show that the fibres are well encapsulated by the coating (conformity) and that structural changes occur, indicating improved functional properties.
Further investigations include adhesion tests and long-term stability assessments. The study provides valuable insights into the application of vacuum coating on paper and opens new possibilities for sustainable and functional materials across various applications. The results and challenges of implementation will be discussed.