Photostructuring of naturally derived resins employing dynamic projection lythography

Photostructuring of Naturally Derived Resins Employing Dynamic Projection Lithograph

Multiscale structuring: investigation of localization and nonlinearity of photopolymerization by varying radiation exposure parameters.

Optical three-dimensional printing (O3DP) is an additive manufacturing technology when a material exposed to light solidifies. Using various light sources – continuous and pulsed – we can achieve different types of light absorption in the material: linear and non-linear absorption. This allows the production of 3D objects with dimensions ranging within 8 orders of magnitude: from hundreds of nanometers to centimeters. Therefore, O3DP has a wide field of applications: from prototyping and small-scale production to the production of micro-optics components, photonics, formation of structures with metamaterial properties, medicine, and tissue engineering. In the dissertation, research was focused on the size of the area of the material exposed to light and manufacturing characteristics. A study of the lateral and longitudinal dimensions of the produced spatial pixels – voxels – was performed depending on the wavelength and pulse duration. The effective degree of absorption was estimated from these data. It was also determined how the polymerization and optical breakdown thresholds change and how this affects the choice of fabrication parameters. Fabrication conditions were investigated in material without photoinitiator using a non-amplified pulse laser system (high repetition rate). A lot of attention has also been paid to the application of plant-derived materials, using linear and nonlinear absorption, and thus demonstrating multiscale O3DP. The results of this thesis showed that to achieve the desired production performance and the size of the manufactured items, it is important not only to modify the properties of the material, but also to be able to widely adjust the parameters of the equipment

Photoinitiator Free Resins Composed of Plant-Derived Monomers for the Optical µ-3D Printing of Thermosets

In this study, acrylated epoxidized soybean oil (AESO) and mixtures of AESO and vanillin dimethacrylate (VDM) or vanillin diacrylate (VDA) were investigated as photosensitive resins for optical 3D printing without any photoinitiator and solvent. The study of photocross-linking kinetics by real-time photorheometry revealed the higher rate of photocross-linking of pure AESO than that of AESO with VDM or VDA. Through the higher yield of the insoluble fraction, better thermal and mechanical properties were obtained for the pure AESO polymer. Here, for the first time, we validate that pure AESO and mixtures of AESO and VDM can be used for 3D microstructuring by employing direct laser writing lithography technique. The smallest achieved spatial features are 1 µm with a throughput in 6900 voxels per second is obtained. The plant-derived resins were laser polymerized using ultrashort pulses by multiphoton absorption and avalanche induced cross-linking without the usage of any photoinitiator. This advances the light-based additive manufacturing towards the 3D processing of pure cross-linkable renewable materials

Molecular changes in endometrium origin stromal cells during initiation of cardiomyogenic differentiation induced with Decitabine, Angiotensin II and TGF- β1

Abstract Stem cells’ differentiation toward cardiac lineage is a complex process dependent on various alterations in molecular basis and regulation pathways. The aim of the study is to show that endometrium-derived stromal cells – menstrual, endometrial and endometriotic, could be an attractive source for examination of the mechanisms underlying cardiomyogenesis. After treatment with Decitabine, Angiotensin II and TGF-β1, cells demonstrated morphological dedifferentiation into early cardiomyocyte-like cells and expressed CD36, CD106, CD172a typically used to sort for human pluripotent stem cell-derived cardiomyocytes. RT-qPCR revealed changed cells’ genetic profiles, as majority of cardiac lineage differentiation related genes and cardiac ion channels (calcium, sodium, potassium) coding genes were upregulated after 6 and 13 days of exposure. Additionally, analysis of expression of various signaling proteins (FOXO1, PDGFB, TGFBR1, mTOR, VEGFA, WNT4, Notch1) coding genes showed differences between cell cultures as they seem to employ distinct signaling pathways through differentiation initiation. Early stages of differentiation had biggest impact on cardiomyogenesis related proteins (Nkx-2.5, EZH2, FOXO3a, H3K9Ac) levels, as we noticed after conducting Western blot and as expected, early cardiac transcription factor Nkx-2.5 was highly expressed and localized in nucleus of differentiating cells. These findings led us to assess endometrium origin stromal cells’ potential to differentiate towards cardiomyogenic lineage and better understand the regulation of complex differentiation processes in ex vivo model systems

Three-dimensional non-destructive visualization of teeth enamel microcracks using X-ray micro-computed tomography

Although the topic of tooth fractures has been extensively analyzed in the dental literature, there is still insufficient information about the potential effect of enamel microcracks (EMCs) on the underlying tooth structures. For a precise examination of the extent of the damage to the tooth structure in the area of EMCs, it is necessary to carry out their volumetric [(three-dimensional (3D)] evaluation. The aim of this study was to validate an X-ray micro-computed tomography (μCT) as a technique suitable for 3D non-destructive visualization and qualitative analysis of teeth EMCs of different severity. Extracted human maxillary premolars were examined using a μCT instrument ZEISS Xradia 520 Versa. In order to separate crack, dentin, and enamel volumes a Deep Learning (DL) algorithm, part of the Dragonfly’s segmentation toolkit, was utilized. For segmentation needs we implemented Dragonfly’s pre-built UNet neural network. The scanning technique which was used made it possible to recognize and detect not only EMCs that are visible on the outer surface but also those that are buried deep inside the tooth. The 3D visualization, combined with DL assisted segmentation, enabled the evaluation of the dynamics of an EMC and precise examination of its position with respect to the dentin-enamel junction

Photocuring and digital light processing 3D printing of vitrimer composed of 2-hydroxy-2-phenoxypropyl acrylate and acrylated epoxidized soybean oil

Vitrimers have gained attention as materials with recyclability, self-healing, and shape memory properties. The use of bio-based monomers for the synthesis of vitrimers is relevant because of the use of an environmentally friendly strategy. In this work, resins based on 2-hydroxy-2-phenoxypropyl acrylate and acrylated epoxidized soybean oil were designed and tested by real-time photorheometry, Fourier transform infrared spectroscopy (FT-IR), and mechanical testing to determine suitability for digital light processing 3D printing. The synthesis of vitrimer that could have good thermal properties and vitrimeric abilities, such as shape memory, self-healing, and recyclability properties, was investigated. Because of this, the vitrimer could repair cracks and defects and could have a complex design of several parts, which also contributes to recyclability and decreases costs. The rigidity and viscosity of the resins were reduced with an increasing amount of 2-hydroxy-2-phenoxypropyl acrylate-based monomer. The resin that has the highest amounts of hydroxyl and ester groups that are beneficial for transesterification reactions was chosen for vitrimer synthesis in order to show vitrimeric abilities such as self-healing, shape memory properties, reprocessability, and recyclability. The synthesized vitrimer was applied to digital light processing 3D printing and showed shape memory with a recovery ratio of 100%, self-healing and reprocessability with an efficiency of 47 and 31% and recyclability properties

Thermo-responsive shape memory vanillin-based photopolymers for microtransfer molding

Novel thermo-responsive shape-memory vanillin-based photopolymers have been developed for microtransfer molding. Different mixtures of vanillin dimethacrylate with tridecyl methacrylate and 1,3-benzenedithiol have been tested as photocurable resins. The combination of the different reaction mechanisms, thiol-acrylate photopolymerization, and acrylate homopolymerization, that were tuned by changing the ratio of monomers, resulted in a wide range of the thermal and mechanical properties of the photopolymers obtained. All polymers demonstrated great shape-memory properties and were able to return to their primary shape after the temperature programming and maintain their temporary shape. The selected compositions weretested by the microtransfer molding technique and showed promising results. The developed thermo-responsive shape-memory bio-based photopolymers have great potential for forming microtransfered structures and devices applicable on non-flat surfaces

Vegetable oil-based thiol-ene/thiol-epoxy resins for laser direct writing 3D micro-/nano-lithography

The use of renewable sources for optical 3D printing instead of petroleum-based materials is increasingly growing. Combinations of photo- and thermal polymerization in dual curing processes can enhance the thermal and mechanical properties of the synthesized thermosets. Consequently, thiol-ene/thiol-epoxy polymers were obtained by combining UV and thermal curing of acrylated epoxidized soybean oil and epoxidized linseed oil with thiols, benzene-1,3-dithiol and pentaerythritol tetra(3-mercaptopropionate). Thiol-epoxy reaction was studied by calorimetry. The changes of rheological properties were examined during UV, thermal and dual curing to select the most suitable formulations for laser direct writing (LDW). The obtained polymers were characterized by dynamicmechanical thermal analysis, thermogravimetry, and mechanical testing. The selected dual curable mixture was tested in LDW 3D lithography for validating its potential in optical micro- and nano- additive manufacturing. The obtained results demonstrated the suitability of epoxidized linseed oil as a biobased alternative to bisphenol A diglycidyl ether in thiol-epoxy thermal curing reactions. Dual cured thermosets showed higher rigidity, tensile strength, and Young’s modulus values compared with UV-cured thiol-ene polymers and the highest thermal stability from all prepared polymers. LDW results proved their suitability for high resolution 3D printing—individual features reaching an unprecedented 100 nm for plant-based materials. Finally, the biobased resin was tested for thermal post-treatment and 50% feature downscaling was achieved