Light-oriented 3D printing of liquid crystal/photocurable resins and in-situ enhancement of mechanical performance.

Additive manufacturing technology has significantly impacted contemporary industries due to its ability to generate intricate computer-designed geometries. However, 3D-printed polymer parts often possess limited application potential, primarily because of their weak mechanical attributes. To overcome this drawback, this study formulates liquid crystal/photocurable resins suitable for the stereolithography technique by integrating 4'-pentyl-4-cyanobiphenyl with a photosensitive acrylic resin. This study demonstrates that stereolithography facilitates the precise modulation of the existing liquid crystal morphology within the resin. Furthermore, the orientation of the liquid crystal governs the oriented polymerization of monomers or prepolymers bearing acrylate groups. The products of this 3D printing approach manifest anisotropic behavior. Remarkably, when utilizing liquid crystal/photocurable resins, the resulting 3D-printed objects are approximately twice as robust as those created using commercial resins in terms of their tensile, flexural, and impact properties. This pioneering approach holds promise for realizing autonomously designed structures that remain elusive with present additive manufacturing techniques.

Exceptional Mechanical Properties and Heat Resistance of Photocurable Bismaleimide Ink for 3D Printing.

Photosensitive resins used in three-dimensional (3D) printing are characterized by high forming precision and fast processing speed; however, they often possess poor mechanical properties and heat resistance. In this study, we report a photocurable bismaleimide ink with excellent comprehensive performance for stereolithography (SLA) 3D printing. First, the main chain of bismaleimide with an amino group (BDM) was synthesized, and then, the glycidyl methacrylate was grafted to the amino group to obtain the bismaleimide oligomer with an unsaturated double bond. The oligomers were combined with reaction diluents and photo-initiators to form photocurable inks that can be used for SLA 3D printing. The viscosity and curing behavior of the inks were studied, and the mechanical properties and heat resistance were tested. The tensile strength of 3D-printed samples based on BDM inks could reach 72.6 MPa (166% of that of commercial inks), glass transition temperature could reach 155 °C (205% of that of commercial inks), and energy storage modulus was 3625 MPa at 35 °C (327% of that of commercial inks). The maximum values of T-5%, T-50%, and Tmax of the 3D samples printed by BDM inks reached 351.5, 449.6, and 451.9 °C, respectively. These photocured BDM inks can be used to produce complex structural components and models with excellent mechanical and thermal properties, such as car parts, building models, and pipes.

Sustained expression of MCP-1 induced low wall shear stress loading in conjunction with turbulent flow on endothelial cells of intracranial aneurysm.

Shear stress was reported to regulate the expression of AC007362, but its underlying mechanisms remain to be explored. In this study, to isolate endothelial cells of blood vessels, unruptured and ruptured intracranial aneurysm (IA) tissues were collected from IA patients. Subsequently, quantitative real-time PCR (qRT-PCR), Western blot and luciferase assay were performed to investigate the relationships between AC007362, miRNAs-493 and monocyte chemoattractant protein-1 (MCP-1) in human umbilical vein endothelial cells (HUVECs) exposed to shear stress. Reduced representation bisulphite sequencing (RRBS) was performed to assess the level of DNA methylation in AC007362 promoter. Accordingly, AC007362 and MCP-1 were significantly up-regulated while miR-493 was significantly down-regulated in HUVECs exposed to shear stress. AC007362 could suppress the miR-493 expression and elevate the MCP-1 expression, and miR-493 was shown to respectively target AC007362 and MCP-1. Moreover, shear stress in HUVECs led to the down-regulated DNA methyltransferase 1 (DNMT1), as well as the decreased DNA methylation level of AC007362 promoter. Similar results were also observed in ruptured IA tissues when compared with unruptured IA tissues. In conclusion, this study presented a deep insight into the operation of the regulatory network of AC007362, miR-493 and MCP-1 upon shear stress. Under shear stress, the expression of AC007362 was enhanced by the inhibited promoter DNA methylation, while the expression of MCP-1 was enhanced by sponging the expression of miR-493.

Effect of Long-term Transcranial Direct Current Stimulation on Glx and GABA: A Pilot Study.

Previous studies have demonstrated that transcranial direct current stimulation (tDCS) over the dorsolateral prefrontal cortex (dlPFC) can enhance working memory. However, the mechanism underlying the long-term tDCS is still unclear. This pilot study aims to examine neurotransmitters such as gamma-aminobutyric (GABA) and Glx (a measure of glutamate and glutamine combined) and working memory in response to the long-term anodal tDCS over dlPFC. Six healthy, right-handed young adults enrolled in this study received 2-mA anodal tDCS over dlPFC within 4 weeks. Long-term tDCS means that it was applied 5 times per week for the first two weeks and once for the last two weeks with 30 min each time. The other six participants were enrolled as the control group without stimulation for testing the baseline enhancement of working memory due to learning. The GABA and Glx levels were assessed by Magnetic Resonance Spectroscopy (MRS), while a 3-back task was performed to assess working memory. Data were collected at the beginning of the experiment, after two-week tDCS and at the end of the experiment. We found that the working memory was not significantly enhanced by the first two-week tDCS because the accuracy of response in 3-back was not significantly increased compared to the control group. Meanwhile, there were no significant changes in the levels of GABA. However, the Glx level was found significantly decreased in both 2- and 4-week MRS measurements. The observation that the long-term tDCS causes the decrease of excitatory neurotransmitters implies the different underlying mechanisms between the long-term tDCS and the single one.

Validation of Numerical Simulation for Transcranial Direct Current Stimulation with Spherical Phantom.

Transcranial direct current stimulation (tDCS) is a promising brain modulation technique in clinical application. Computational models of brain current flow have been used to provide better insights into determining the stimulation parameters, but there are only a few studies to validate the numerical simulation model. The purpose of this study is to validate the simulation model of tDCS. A one-/three-layered spherical phantom model was constructed to mimic the human head. The tDCS-induced voltages were measured at different depth in the spherical phantom model with stereotactic-EEG (s-EEG) electrodes. Comparing the measured values with the simulation data from the computational models, we found that the computational and empirically measured electric field distributions on the brain surface is similar and that the deviation between the predicted and measured electric field value becomes larger near the electrode.

Tunable Wavelength Enhanced Photoelectrochemical Cells from Surface Plasmon Resonance.

Photocatalysis is a promising technology for renewable energy production. Many photocatalysis have realized the visible-light-driven catalytic activity. However, it is still difficult to achieve the enhanced photocatalytic activity with tunable wavelength. We have designed tunable wavelength enhanced photoelectrochemical cells by tuning the surface plasmon resonance (SPR) peaks, which can be controlled by the aspect ratios of the Au nanorods, for both the cathode with the hydrogen evolution reaction and the anode with the electrooxidation of methanol reaction. The optimal photocatalytic activity of the hydrogen evolution and electrooxidation of the methanol can be realized only when the illuminating wavelength matches with the SPR peaks, which is quite selective to the illuminating wavelength. The blue shift of the SPR peak increases the photoelectrocatalytic effect whereas the red shift enhances the photothermal effect. Such studies provide a useful way for improving the photocatalytic activity and the selectivity of the photocatalytic reactions by adjusting the illuminating wavelength.