DLIP on Freeform Surfaces: Structure Homogeneity via Acoustic-Based Process Control

This presentation explores advanced approaches in Direct Laser Interference Patterning (DLIP) for texturing freeform surfaces with complex geometries, such as those used in medical implants and technical components. DLIP enables the efficient generation of biomimetic micro- and nanostructures that significantly enhance surface functionality. The integration of the process into multi-axis CNC systems allows for precise alignment and surface adaptation on non-planar parts.

A key innovation is the use of acoustic emission (AE) monitoring as a real-time process control method. Acoustic signals generated during DLIP are captured using a MEMS microphone positioned near the processing zone. A closed-loop PI control system dynamically adjusts the laser power based on AE signal feedback to ensure consistent structure depth and homogeneity.

Demonstrators include LPBF-manufactured beta-titanium samples, TPMS structures, and curved stainless steel profiles. Besides these applications, the AE-based control reduced structure depth deviations from 0.50?µm to 0.13?µm, achieving a highly uniform texture. Additionally, structure homogeneity was quantified using the Gini coefficient, with values improving from 0.79 to 0.94 using optimized beam configurations.

The work highlights the potential of combining adaptive DLIP technologies with in-situ sensing for high-quality, scalable surface functionalization. These methods pave the way for robust, application-specific manufacturing of advanced implants and technical surfaces with improved biointegration and performance.

About the presenter
Christoph Zwahr, Ph.D., leads the department of Laser Precision Manufacturing at Fraunhofer IWS Dresden. His research focuses on laser-based surface functionalization, in particular the integration of Direct Laser Interference Patterning (DLIP) with adaptive process control strategies. With a background in mechanical engineering and laser manufacturing, he works on applying structured surfaces to technical and biomedical components. He holds a doctorate from TU Dresden and is active in national and EU research consortia.