Abstract
Two-photon polymerization (TPP) is capable of fabricating 3D structures with dimensions from sub-µm to a few hundred µm. As a direct laser writing (DLW) process, fabrication time of 3D TPP structures scale with the third order, limiting its use in large volume fabrication. Here, we report on a scalable fabrication method that cuts fabrication time to a fraction. A parallelized 9 multi-beamlets DLW process, created by a fixed diffraction optical element (DOE) and subsequent stitching are used to fabricate large periodic high aspect ratio 3D microstructured arrays with sub-micron features spanning several hundred of µm2. The wall structure in the array is designed with a minimum of traced lines and is created by a low numerical aperture (NA) microscope objective, leading to self-supporting lines omitting the need for line-hatching. The fabricated periodic arrays are applied in a cell – 3D microstructure interaction study using living HeLa cells. First indications of increased cell proliferation in the presence of 3D microstructures compared to planar surfaces are obtained. Furthermore, the cells adopt an elongated morphology when attached to the 3D microstructured surfaces. Both results constitute promising findings rendering the 3D microstructures a suited tool for cell interaction experiments, e.g. for cell migration, separation or even tissue engineering studies.
Highlights
For increased voxel movement speed the translation speed of stage scanning systems is typically the limiting factor for this approach, while inside the field-of-view (FOV) of the focusing objective the voxel speed can significantly be increased by using galvo-scanning mirrors[12]
We have demonstrated a scalable method for fast fabrication of large volume scaffold structures with the potential for cell and tissue engineering
We demonstrate how parallelization of the direct laser writing (DLW) process by a fixed diffractive optical element (DOE) cuts the fabrication time to a fraction for large unit structures, while maintaining sub-micrometer features in each unit structure
Summary
For increased voxel movement speed the translation speed of stage scanning systems is typically the limiting factor for this approach, while inside the field-of-view (FOV) of the focusing objective the voxel speed can significantly be increased by using galvo-scanning mirrors[12]. Recent developments in high pulse power kHz repetition rate lasers and micro-mirror arrays have made it possible to reach massive parallelization of the TPP process with up to a million pixels[29,30]. We demonstrate a scalable fast fabrication strategy for large volume continuous 3D structures containing sub-micrometer features. Such feature sizes are found in biology, where extracellular matrices contain networks with few micrometer fibrous structures[31], while individual cells typically reach length scales of tens of micrometers. Various emerging research approaches make use of 3D polymer microstructures to develop an increased understanding via in vitro studies in various areas of medical research relevance, concretely in the area of cancer[31,34,35], neuronal[25,36,37,38], primary/stem cell research[39,40,41,42,43,44,45] and even reached in vivo applications[46]
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