ISBN 9783843956505

978-3-8439-5650-5, Reihe Mikrosystemtechnik

Ha-Neul Chae
Fabrication of Hairy structures using Two-Photon Lithography and CHic chemistry

116 Seiten, Dissertation Albert-Ludwigs-Universität Freiburg im Breisgau (2025), Softcover, B5

Zusammenfassung / Abstract

Organisms in nature exhibit surface structures that regulate interactions with their environment, enabling functionalities such as wetting control, self-cleaning, adhesion, and moisture harvesting. In particular, dense hair-like structures play a significant role due to their unique physical properties, making them a key inspiration for the development of functional biomimetic surfaces. In this study, a fabrication process based on two-photon lithography (2PL), in particular two-photon crosslinking (2PC), was developed to precisely construct such high-aspect-ratio microstructures.

This method utilizes two-photon absorption of chromophores within a polymer matrix to induce localized crosslinking. After exposure, non-crosslinked regions are removed by solvent development, yielding ultrafine, freestanding hair-like structures. Both individual hairs and dense hair arrays (up to ~1.5 mm²) were fabricated; however, structural bundling was observed due to hydrophobic interactions during drying.

To overcome this issue and improve fabrication efficiency, lattice- and trench-based designs were introduced, enabling the production of clean, non-bundled structures over larger areas (up to 5 mm²) in shorter times. The resolution of the fabricated structures was found to depend on fabrication parameters such as laser intensity, exposure time, slicing and hatching distances. Additionally, the range between the percolation threshold and degradation threshold varied depending on the type of crosslinker and polymer composition. Based on these findings, a process optimization model for 2PC was proposed. This work presents a novel approach for the precise fabrication of biomimetic surface structures, enabling improved control and functional performance.