Self-cleaning mechanisms on laser-induced surface structures – the role of surface topography and energy on particle removal

• Applicants: Dr.-Ing. Georg Schnell; Dr.-Ing. Stefan Schröder
• Subject Area: Synthesis and Properties of Functional Materials
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 567110535

Self-cleaning is a property observed in nature on certain organisms and is used by humans to realize the dream of a contamination-free surface. Removing dirt or contamination without one's own effort has triggered the development of various concepts of artificial self-cleaning surfaces, mostly based on superhydrophobicity or photocatalysis. The research on self-cleaning surfaces is not only of fundamental interest, but rather can have practicle application in daily life and industry. Essential for self-cleaning is the topography and energy of the involved surface and contamination. However, the exact role of and interaction of surface topography and surface energy are still under debate. Inspired by nature, this project will clarify the impact of surface topography and surface energy on the self-cleaning ability of laser-functionalized surfaces. The forces that act during particle detachment will be modified by initiated chemical vapor deposition and laser-assisted nano- and micro-texturing. Using an advanced force-based goniometer setup, fundamental insights into the detachment of particles will be developed to tailor the self-cleaning ability of ultrashort-pulsed laser processed and functionalized surfaces with high potential for large-scale applications. The University of Rostock will generate surface topographies with varying nano- and microcavities on stainless steel by USPL treatment. Those SE will be precisely tailored by initiierte chemische Gasphasenabscheidung, resulting in ultra-thin polymer films by Kiel University. In addition, the particle surface energy will be modified by initiierte chemische Gasphasenabscheidung of nano- to microsized beads to generate a particle mixture that reflects real-world contaminations as far as possible. Using an established droplet adhesion force instrument coupled with a fluorescence microscope, the simultaneous tracking of lateral adhesion forces and the visualization of particle detachment by moving droplets is possible. This enables qualitative and quantitive insights into the particle removal on the tailored surfaces to reveal the impact of surface topography and surface energy on self-cleaning. Furthermore, Fluorine-free molecules will be developed to provide a sustainable solution for the chemical modification of laser-structured surfaces. The focus will be on bonding the polymers to ultrashort-pulsed laser-treated surfaces to face harsh environments. Starting on the stainless-steel substrate, which enables unique surface topographies by ultrashort-pulsed laser processing and is relevant for many industrial applications on self-cleaning (e.g., food industry), findings will be transferred to a glass substrate and photovoltaic application in the funding period 2.

• DFG Programme: Research Grants
• Co-Investigators: Professor Dr. Franz Faupel; Professor Dr.-Ing. Hermann Seitz