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Two-photon polymerization (2PP) is a lithography-based 3D printing method allowing the fabrication of 3D structures with sub-micrometer resolution. This work focuses on the characterization of gelatin-norbornene (Gel-NB) bioinks which enables the embedding of cells via 2PP. The high reactivity of the thiol-ene system allows 2PP processing of cell-containing materials at remarkably high scanning speeds (1000 mm s(-1)) placing this technology in the domain of bioprinting. Atomic force microscopy results demonstrate that the indentation moduli of the produced hydrogel constructs can be adjusted in the 0.2-0.7 kPa range by controlling the 2PP processing parameters. Using this approach gradient 3D constructs are produced and the morphology of the embedded cells is observed in the course of 3 weeks. Furthermore, it is possible to tune the enzymatic degradation of the crosslinked bioink by varying the applied laser power. The 3D printed Gel-NB hydrogel constructs show exceptional biocompatibility, supported cell adhesion, and migration. Furthermore, cells maintain their proliferation capacity demonstrated by Ki-67 immunostaining. Moreover, the results demonstrate that direct embedding of cells provides uniform distribution and high cell loading independently of the pore size of the scaffold. The investigated photosensitive bioink enables high-definition bioprinting of well-defined constructs for long-term cell culture studies.

Two-photon polymerization (2PP) is a lithography-based 3D printing method allowing the fabrication of 3D structures with sub-micrometer resolution. This work focuses on the characterization of gelatin-norbornene (Gel-NB) bioinks which enables the embedding of cells via 2PP. The high reactivity of the thiol-ene system allows 2PP processing of cell-containing materials at remarkably high scanning speeds (1000 mm s(-1)) placing this technology in the domain of bioprinting. Atomic force microscopy results demonstrate that the indentation moduli of the produced hydrogel constructs can be adjusted in the 0.2-0.7 kPa range by controlling the 2PP processing parameters. Using this approach gradient 3D constructs are produced and the morphology of the embedded cells is observed in the course of 3 weeks. Furthermore, it is possible to tune the enzymatic degradation of the crosslinked bioink by varying the applied laser power. The 3D printed Gel-NB hydrogel constructs show exceptional biocompatibility, supported cell adhesion, and migration. Furthermore, cells maintain their proliferation capacity demonstrated by Ki-67 immunostaining. Moreover, the results demonstrate that direct embedding of cells provides uniform distribution and high cell loading independently of the pore size of the scaffold. The investigated photosensitive bioink enables high-definition bioprinting of well-defined constructs for long-term cell culture studies.

Ion emitter instruments ASPOC (Active Spacecraft Potential Control) have been used successfully in several magnetospheric missions including the ESA Cluster Project. An improved version has been developed for the equatorial spacecraft of the Chinese-European Double Star mission (TC-1) launched in December 2003. The modifications include a new design of the ion emitter modules. As a result, higher currents than in previous missions can be achieved. The main objective of the investigation lies in a reduction of positive spacecraft potential in order to minimize the perturbations to the plasma measurements on board, in particular to the plasma electron instrument PEACE. These data show an almost complete suppression of photo-electrons when ASPOC is emitting at 30 to 50 micro-A beam current. The angular distribution of the electrons in the presence of the ion beam is investigated in detail. The measurement of ambient electron distributions is highly improved., 資料番号: AA0049206091, レポート番号: JAXA-SP-05-001E

The Z-Scan technique has become a standard method to characterize higher order nonlinearities such as two-photon absorption, which have found applications from 3D nanolithography to high-resolution 3D microscopy. However, usually Z-scan is performed at one single wavelength, providing only limited information on the spectral characteristic of compounds like photoinitiators and fuorescent dyes. The aim of this thesis was to design a fully automated Z-Scan to characterize the nonlinear absorption properties of different compounds. This novel setup was based on a tunable high-power femtosecond oscillator, allowing scans from 690-1040 nanometers. A beam profiling method was implemented to efficiently extract the parameters of the focused beam. For the Z-Scan Rhodamine B was selected as reference material, since its cross section is well known in literature. Compared to conventional amplified systems oscillator based Z-Scans can lead to thermal effects due to the high average power, which compromise the results. These effects were reduced by installing a beam chopper and adapting the software accordingly. The modifications allowed successful Z-Scan measurements which were comparable to Z-Scans using amplified systems. Therefore, the oscillator based Z-Scan shows promise as a tool for spectral analysis of two-photon absorption.