In-Operando Study of Shape Retention and Microstructure Development in a Hydrolyzing Sol-Gel Ink during 3D-Printing

A route toward fabrication of 3D printed bone scaffolds based on poly(vinyl alcohol)-chitosan/bioactive glass by sol-gel chemistry

Among different methods for the fabrication of bone scaffolds, 3D printing has created great advances in tissue engineering and regenerative medicine owing to its ability to make objects mimicking native tissues. Thanks to its abundant availability, structural features, and favorable biological properties, chitosan (CS) hydrogel was selected to be used for preparation of the bone scaffolds. However, the 3D printing of CS-based hydrogels is still under early exploration. Knowing the fact that natural polymers are not so competent at holding large amounts of water, poly(vinyl alcohol) as the second polymer was employed. The novelty of the present research lies in the concept of employing sol-gel chemistry in order to attain proper viscosity and rheological behavior to give self-standing filaments of the polymer blends. Employing sol-gel reaction in the preparation of the hybrid hydrogels had the advantage of endowing shape fidelity to the polymer blend without any solidifying in the needle. The obtained organic-inorganic hybrids were directly printed and subsequently cross-linked. The best performance in terms of mechanical strength, cell viability, and bio-mineralization was observed for the 50:50 ratio. The in vitro cell culture and the bioactivity results showed that the printed scaffolds with this method have great potential in bone tissue engineering. Further, this method could be expandable to print other hydrogels with diverse applications such as implantable devices, soft robotics, etc.

Operando Characterization of Organic Mixed Ionic/Electronic Conducting Materials

Operando characterization plays an important role in revealing the structure-property relationships of organic mixed ionic/electronic conductors (OMIECs), enabling the direct observation of dynamic changes during device operation and thus guiding the development of new materials. This review focuses on the application of different operando characterization techniques in the study of OMIECs, highlighting the time-dependent and bias-dependent structure, composition, and morphology information extracted from these techniques. We first illustrate the needs, requirements, and challenges of operando characterization then provide an overview of relevant experimental techniques, including spectroscopy, scattering, microbalance, microprobe, and electron microscopy. We also compare different in silico methods and discuss the interplay of these computational methods with experimental techniques. Finally, we provide an outlook on the future development of operando for OMIEC-based devices and look toward multimodal operando techniques for more comprehensive and accurate description of OMIECs.

Heterogeneous dynamics in the curing process of epoxy resins

Epoxy resin is indispensable for modern industry because of its excellent mechanical properties, chemical resistance, and excellent moldability. To date, various methods have been used to investigate the physical properties of the cured product and the kinetics of the curing process, but its microscopic dynamics have been insufficiently studied. In this study, the microscopic dynamics in the curing process of a catalytic epoxy resin were investigated under different temperature conditions utilizing X-ray photon correlation spectroscopy. Our results revealed that the temperature conditions greatly affected the dynamical heterogeneity and cross-linking density of the cured materials. An overview of the microscopic mechanism of the curing process was clearly presented through comparison with the measurement results of other methods, such as 1H-pulse nuclear magnetic resonance spectroscopy. The quantification of such heterogeneous dynamics is particularly useful for optimizing the curing conditions of various materials to improve their physical properties.

Synchrotron Microbeam Diffraction Studies on the Alignment within 3D-Printed Smectic-A Liquid Crystal Elastomer Filaments during Extrusion

3D printing of novel and smart materials has received considerable attention due to its applications within biological and medical fields, mostly as they can be used to print complex architectures and particular designs. However, the internal structure during 3D printing can be problematic to resolve. We present here how time-resolved synchrotron microbeam Small-Angle X-ray Diffraction (μ-SAXD) allows us to elucidate the local orientational structure of a liquid crystal elastomer-based printed scaffold. Most reported 3D-printed liquid crystal elastomers are mainly nematic; here, we present a Smectic-A 3D-printed liquid crystal elastomer that has previously been reported to promote cell proliferation and alignment. The data obtained on the 3D-printed filaments will provide insights into the internal structure of the liquid crystal elastomer for the future fabrication of liquid crystal elastomers as responsive and anisotropic 3D cell scaffolds.