Two-photon polymerization as method for the fabrication of large scale biomedical scaffold applications

Two-photon polymerization (2PP) using ultra-short laser pulses is a well-known methodology for the 3D free-form fabrica-tion of optical devices with resolutions down to 100 nm. However, the structure dimensions have been restricted to quite small sizes, mainly due to limitations of the focussing optics and due to very long fabrication times. Therefore, the large-scale fabrication of biomedical scaffold structures with dimensions in the mm-range still remains challenging. Using a diode-pumped Ytterbium laser system emitting 325 fs laser pulses at 515 nm after second harmonic generation we are able to write arbitrary 3D structures in inorganic-organic hybrid polymers (ORMOCER®s). Our setup is able to produce structures with mm extension normal to the substrate at a structural resolution of a few microns. In particular, a 3D porous inner structure can be provided, which is required for three-dimensional cell growth to support cell adhesion and prolifera-tion. Scaffold stru ctures were produced with different parameters, and they were characterized in order to demonstrate their potential concerning resolution and scaffold quality. It is found that not only the experimental setup, but also the substrate material plays an important role for the scaffold fabrication process and structural quality

Compensation of spherical aberration influences for two-photon polymerization patterning of large 3D scaffolds

Two-photon polymerization using femtosecond laser pulses at a wavelength of 515 nm is used for three-dimensional patterning of photosensitive, biocompatible inorganic-organic hybrid polymers (ORMOCER(A (R))s). In order to fabricate millimeter-sized biomedical scaffold structures with interconnected pores, medium numerical aperture air objectives with long working distances are applied which allow voxel lengths of several micrometers and thus the solidification of large scaffolds in an adequate time. It is demonstrated that during processing the refraction of the focused laser beam at the air/material interface leads to strong spherical aberration which decreases the peak intensity of the focal point spread function along with shifting and severely extending the focal region in the direction of the beam propagation. These effects clearly decrease the structure integrity, homogeneity and the structure details and therefore are minimized by applying a positioning and laser power adaptation throughout the fabrication process. The results will be discussed with respect to the resulting structural homogeneity and its application as biomedical scaffold

Immobilization of ionic liquids within micro- and mesoporous materials

Room temperature imidazolium-based ionic liquid (1-ethyl-3-methylimidazolium tetrafluoroborate) was immobilized within high-silica zeolite Beta and mesoporous silica (SBA-15) samples using methanol as solvent. The resultant samples were then subjected to Soxhlet extraction in order to remove the ionic liquids which are loosely bound on the external surfaces. All the samples (before and after Soxhlet extraction) were analyzed by TG-DTA, 13C MAS-NMR and N2-adsorption measurements. Upon immobilization of ionic liquid, the BET surface areas of the host materials decreased significantly. Nevertheless, the ionic liquid immobilized host materials regained their surface areas after Soxhlet extraction. The amount of immobilized ionic liquid was estimated from TG measurements to be 0.6 wt.% (zeolite Beta) and 1.3 wt.% (SBA-15), respectively

Nanostructured ZnFeZr oxyhydroxide precipitate as efficient phosphate adsorber in waste water understanding the role of different material building blocks

We present investigations on the working principle of a new adsorber for the recycling of phosphate from waste water.</p

Effects of vibrations and shocks in electric vehicles on Li-ion batteries

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