Facile fabrication of a three-dimensional colloidal crystal film with large-area and robust mechanical properties

Biomimetic structures such as structural colors demand a fabrication technology of complex three-dimensional nanostructures on large areas. Nanoimprint lithography (NIL) is capable of large area replication of three-dimensional structures, but the master stamp fabrication is often a bottleneck. We have demonstrated different approaches allowing for the generation of sophisticated undercut T-shaped masters for NIL replication. With a layer-stack of phase transition material (PTM) on poly-Si, we have demonstrated the successful fabrication of a single layer undercut T-shaped structure. With a multilayer-stack of silicon oxide on silicon, we have shown the successful fabrication of a multilayer undercut T-shaped structures. For patterning optical lithography, electron beam lithography and nanoimprint lithography have been compared and have yielded structures from 10 µm down to 300 nm. The multilayer undercut T-shaped structures closely resemble the geometry of the surface of a Morpho butterfly, and may be used in future to replicate structural colors on artificial surfaces.

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Is Dialdehyde Chitosan a Good Substance to Modify Physicochemical Properties of Biopolymeric Materials?

International Journal of Molecular Sciences ◽

10.3390/ijms22073391 ◽

2021 ◽

Vol 22 (7) ◽

pp. 3391

Author(s):

Sylwia Grabska-Zielińska ◽

Alina Sionkowska ◽

Ewa Olewnik-Kruszkowska ◽

Katarzyna Reczyńska ◽

Elżbieta Pamuła

Keyword(s):

Mechanical Properties ◽

Tissue Engineering ◽

Physicochemical Properties ◽

Silk Fibroin ◽

Three Dimensional ◽

Microscopy Imaging ◽

Maximum Deformation ◽

One Step ◽

Chitosan Blends ◽

Fourier Transfer Infrared Spectroscopy

The aim of this work was to compare physicochemical properties of three dimensional scaffolds based on silk fibroin, collagen and chitosan blends, cross-linked with dialdehyde starch (DAS) and dialdehyde chitosan (DAC). DAS was commercially available, while DAC was obtained by one-step synthesis. Structure and physicochemical properties of the materials were characterized using Fourier transfer infrared spectroscopy with attenuated total reflectance device (FTIR-ATR), swelling behavior and water content measurements, porosity and density observations, scanning electron microscopy imaging (SEM), mechanical properties evaluation and thermogravimetric analysis. Metabolic activity with AlamarBlue assay and live/dead fluorescence staining were performed to evaluate the cytocompatibility of the obtained materials with MG-63 osteoblast-like cells. The results showed that the properties of the scaffolds based on silk fibroin, collagen and chitosan can be modified by chemical cross-linking with DAS and DAC. It was found that DAS and DAC have different influence on the properties of biopolymeric scaffolds. Materials cross-linked with DAS were characterized by higher swelling ability (~4000% for DAS cross-linked materials; ~2500% for DAC cross-linked materials), they had lower density (Coll/CTS/30SF scaffold cross-linked with DAS: 21.8 ± 2.4 g/cm3; cross-linked with DAC: 14.6 ± 0.7 g/cm3) and lower mechanical properties (maximum deformation for DAC cross-linked scaffolds was about 69%; for DAS cross-linked scaffolds it was in the range of 12.67 ± 1.51% and 19.83 ± 1.30%) in comparison to materials cross-linked with DAC. Additionally, scaffolds cross-linked with DAS exhibited higher biocompatibility than those cross-linked with DAC. However, the obtained results showed that both types of scaffolds can provide the support required in regenerative medicine and tissue engineering. The scaffolds presented in the present work can be potentially used in bone tissue engineering to facilitate healing of small bone defects.

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3D Printing of High Viscosity Reinforced Silicone Elastomers

Polymers ◽

10.3390/polym13142239 ◽

2021 ◽

Vol 13 (14) ◽

pp. 2239

Author(s):

Nicholas Rodriguez ◽

Samantha Ruelas ◽

Jean-Baptiste Forien ◽

Nikola Dudukovic ◽

Josh DeOtte ◽

...

Keyword(s):

Mechanical Properties ◽

High Performance ◽

New Technologies ◽

Three Dimensional ◽

High Viscosity ◽

Layer By Layer ◽

Silicone Elastomers ◽

Uv Curable ◽

Octet Truss ◽

Tunable Mechanical Properties

Recent advances in additive manufacturing, specifically direct ink writing (DIW) and ink-jetting, have enabled the production of elastomeric silicone parts with deterministic control over the structure, shape, and mechanical properties. These new technologies offer rapid prototyping advantages and find applications in various fields, including biomedical devices, prosthetics, metamaterials, and soft robotics. Stereolithography (SLA) is a complementary approach with the ability to print with finer features and potentially higher throughput. However, all high-performance silicone elastomers are composites of polysiloxane networks reinforced with particulate filler, and consequently, silicone resins tend to have high viscosities (gel- or paste-like), which complicates or completely inhibits the layer-by-layer recoating process central to most SLA technologies. Herein, the design and build of a digital light projection SLA printer suitable for handling high-viscosity resins is demonstrated. Further, a series of UV-curable silicone resins with thiol-ene crosslinking and reinforced by a combination of fumed silica and MQ resins are also described. The resulting silicone elastomers are shown to have tunable mechanical properties, with 100–350% elongation and ultimate tensile strength from 1 to 2.5 MPa. Three-dimensional printed features of 0.4 mm were achieved, and complexity is demonstrated by octet-truss lattices that display negative stiffness.

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Radial Turbine Design for Solar Chimney Power Plants

Energies ◽

10.3390/en14030674 ◽

2021 ◽

Vol 14 (3) ◽

pp. 674

Author(s):

Paul Caicedo ◽

David Wood ◽

Craig Johansen

Keyword(s):

Power Plants ◽

Reference Frames ◽

Three Dimensional ◽

Discrete Ordinates ◽

Large Area ◽

Solar Chimney ◽

Cfd Simulations ◽

Radial Turbine ◽

Design Changes ◽

Turbine Design

Solar chimney power plants (SCPPs) collect air heated over a large area on the ground and exhaust it through a turbine or turbines located near the base of a tall chimney to produce renewable electricity. SCPP design in practice is likely to be specific to the site and of variable size, both of which require a purpose-built turbine. If SCPP turbines cannot be mass produced, unlike wind turbines, for example, they should be as cheap as possible to manufacture as their design changes. It is argued that a radial inflow turbine with blades made from metal sheets, or similar material, is likely to achieve this objective. This turbine type has not previously been considered for SCPPs. This article presents the design of a radial turbine to be placed hypothetically at the bottom of the Manzanares SCPP, the only large prototype to be built. Three-dimensional computational fluid dynamics (CFD) simulations were used to assess the turbine’s performance when installed in the SCPP. Multiple reference frames with the renormalization group k-ε turbulence model, and a discrete ordinates non-gray radiation model were used in the CFD simulations. Three radial turbines were designed and simulated. The largest power output was 77.7 kW at a shaft speed of 15 rpm for a solar radiation of 850 W/m2 which exceeds by more than 40 kW the original axial turbine used in Manzanares. Further, the efficiency of this turbine matches the highest efficiency of competing turbine designs in the literature.

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Conductive GelMA–Collagen–AgNW Blended Hydrogel for Smart Actuator

Polymers ◽

10.3390/polym13081217 ◽

2021 ◽

Vol 13 (8) ◽

pp. 1217

Author(s):

Jang Ho Ha ◽

Jae Hyun Lim ◽

Ji Woon Kim ◽

Hyeon-Yeol Cho ◽

Seok Geun Jo ◽

...

Keyword(s):

Mechanical Properties ◽

Umbilical Vein ◽

Three Dimensional ◽

Silver Nanowire ◽

Structural Deformation ◽

Rheological Analysis ◽

Sem Image ◽

Smart Actuator ◽

Umbilical Vein Endothelial Cells ◽

Electrical Stimuli

Blended hydrogels play an important role in enhancing the properties (e.g., mechanical properties and conductivity) of hydrogels. In this study, we generated a conductive blended hydrogel, which was achieved by mixing gelatin methacrylate (GelMA) with collagen, and silver nanowire (AgNW). The ratio of GelMA, collagen and AgNW was optimized and was subsequently gelated by ultraviolet light (UV) and heat. The scanning electron microscope (SEM) image of the conductive blended hydrogels showed that collagen and AgNW were present in the GelMA hydrogel. Additionally, rheological analysis indicated that the mechanical properties of the conductive GelMA–collagen–AgNW blended hydrogels improved. Biocompatibility analysis confirmed that the human umbilical vein endothelial cells (HUVECs) encapsulated within the three-dimensional (3D), conductive blended hydrogels were highly viable. Furthermore, we confirmed that the molecule in the conductive blended hydrogel was released by electrical stimuli-mediated structural deformation. Therefore, this conductive GelMA–collagen–AgNW blended hydrogel could be potentially used as a smart actuator for drug delivery applications.

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