Microgroove Width Research Articles

Performance of flexible CeO2 composite abrasive in force rheological polishing of fused silica glass

Polishing is critical for obtaining high-quality surfaces on fused silica glass components, which are used extensively in numerous civil and military applications. The abrasive used in conventional polishing processes is typically on the microscale or nanoscale. This study prepared a millimeter-scale flexible composite abrasive consisting of a natural rubber (NR) core coated with CeO2 for use in force rheological polishing (FRP), aiming to improve efficiency and material removal selectivity without compromising surface quality. An analysis of the synthesized abrasive indicated that the CeO2 exhibited excellent adhesion to the surface of the rubber core. The results of polishing experiments conducted on fused silica glass workpieces using the proposed composite abrasive indicated that following 20 min of FRP, the surface roughness (Sa) of the workpiece was reduced from 464.2 nm to 2.2 nm and a high material removal rate (MRR) of 337.2 nm/min was achieved with negligible damage to the surface. The utilization of the composite abrasive for FRP effectively promoted the chemical reaction between CeO2 and silica glass to achieve rapid material removal. Furthermore, the material removal selectivity characteristics of the composite abrasive were investigated by polishing micro-grooved surfaces. The resulting groove contours and morphologies revealed that the composite abrasive played a crucial role in selectively removing material from the edges and bottoms of the micro-grooves such that elevated points experienced more extensive material removal, realizing a flatter surface. However, the effectiveness of selective removal diminished as the micro-groove width increased. The results of this study furnish compelling theoretical and experimental evidence supporting the utilization of millimeter-scale flexible composite abrasives in FRP.

Effect of Femtosecond‐Laser‐Induced Surface Textures on the Microstructure and Mechanical Properties of Mg/Ti Dissimilar Alloys Laser Lap Welds: A Numerical and Experimental Study

The strength of the joints in the Mg/Ti laser welding is difficult to meet the requirement because of the metallurgical incompatibility. This study investigates the influence of microgroove width on the diffusion of molten Mg and the mechanical properties of joints by laser welding Ti6Al4V and AZ31B, employing femtosecond lasers to fabricate microgrooves on the surface of Ti alloys. The optimal contact angle of 56.4° is achieved at the microgroove width of 100 μm because the leading and trailing edges of the microgroove texture can stimulate the formation of the microriveted structure, facilitating the fluidity of the liquid AZ31B. The joint's tensile–shear capability is increased to 2449.9 N, which is 2.8 times stronger compared to joints without microgroove textures, when using a microgroove width of 100 μm and a laser power of 52%. The numerical simulation of the laser welding process was implemented to analyze the temperature field and the fluid characteristics within the melt pool. In the results, it is shown that the microgroove enhanced the material exchange at the interface and accelerated the interfacial reaction, which stimulates the formation of Ti–Al and Mg–Al intermetallic compounds at the central interface of the joint and enhances the Mg/Ti metallurgical bonding.

Spatial Constraints of Rectangular Hydrogel Microgrooves Regulate the Morphology and Arrangement of Human Umbilical Vein Endothelial Cells

To construct microscale rectangular hydrogel grooves and to investigate the morphology and alignment of human umbilical vein endothelial cells (HUVECs) under spatial constraints. Vascular endothelial cell morphology and alignment are important factors in vascular development and the maintenance of homeostasis. A 4-arm polyethylene glycol-acrylate (PEG-acrylate) hydrogel was used to fabricate rectangular microgrooves of the widths of 60 μm, 100 μm, and 140 μm. The sizes and the fibronectin (FN) adhesion of these hydrogel microgrooves were measured. HUVECs were seeded onto the FN-coated microgrooves, while the flat surface without micropatterns was used as the control. After 48 hours of incubation, the morphology and orientation of the cells were examined. The cytoskeleton was labelled with phalloidine and the orientation of the cytoskeleton in the hydrogel microgrooves was observed by laser confocal microscopy. The hydrogel microgrooves constructed exhibited uniform and well-defined morphology, a complete structure, and clear edges, with the width deviation being less than 3.5%. The depth differences between the hydrogel microgrooves of different widths were small and the FN adhesion is uniform, providing a micro-patterned growth interface for cells. In the control group, the cells were arranged haphazardly in random orientations and the cell orientation angle was (46.9±1.8)°. In contrast, the cell orientation angle in the hydrogel microgrooves was significantly reduced (P<0.001). However, the cell orientation angles increased with the increase in hydrogel microgroove width. For the 60 μm, 100 μm, and 140 μm hydrogel microgrooves, the cell orientation angles were (16.4±2.8)°, (24.5±3.2)°, and (30.3±3.5)°, respectively. Compared to that of the control group (35.7%), the number of cells with orientation angles <30° increased significantly in the hydrogel microgrooves of different widths (P<0.001). However, as the width of the hydrogel microgrooves increased, the number of cells with orientation angles <30° gradually decreased (79.9%, 62.3%, 54.7%, respectively), while the number of cells with orientation angles between 60°-90° increased (P<0.001). The cell bodies in the microgrooves were smaller and more rounded in shape. The cells were aligned along the direction of the microgrooves and corresponding changes occurred in the arrangement of the cell cytoskeleton. In the control group, cytoskeletal filaments were aligned in random directions, presenting an orientation angle of (45.5±3.7)°. Cytoskeletal filaments were distributed evenly within various orientation angles. However, in the 60 μm, 100 μm, and 140 μm hydrogel microgrooves, the orientation angles of the cytoskeletal filaments were significantly decreased, measuring (14.4±3.1)°, (24.7±3.5)°, and (31.9±3.3)°, respectively. The number of cytoskeletal filaments with orientation angles <30° significantly increased in hydrogel microgrooves of different widths (P<0.001). However, as the width of the hydrogel microgrooves increased, the number of cytoskeletal filaments with orientation angles <30° gradually decreased, while the number of cytoskeletal filaments with orientation angles between 60°-90° gradually increased (P<0.001). Hydrogel microgrooves can regulate the morphology and orientation of HUVECs and mimic to a certain extent the in vivo microenvironment of vascular endothelial cells, providing an experimental model that bears better resemblance to human physiology for the study of the unique physiological functions of vascular endothelial cells. Nonetheless, the molecular mechanism of spatial constraints on the morphology and the assembly of vascular endothelial cell needs to be further investigated.

Experimental Investigation of the Derivative Cutting When Machining AISI 1045 with Micro-Textured Cutting Tools

In the context of satisfying sustainability requirements nowadays, dry machining is one of the ideal strategies to eliminate the environmental and human health burdens of machining processes. In addition, micro-textured cutting tools are used to improve the performance of dry machining processes. Micro-textures reduce the chip-tool contact length and thus reduce friction and heat, which results in fewer cutting forces and temperature. However, the action of micro-cutting of the bottom side of the chip, which is known as derivative cutting, cuts down the gains of using textured tools, where derivative cutting leads to higher cutting forces, heat, and tool wear. This study aimed to investigate the effects of significant texture design parameters (i.e., micro-groove width) when cutting AISI 1045 steel using different machining parameters (i.e., 75 m/min and 150 m/min of cutting velocity, 0.05 and 0.10 mm/rev of feed). Three different textured cutting tool designs were prepared using the laser texturing technique and then utilized in machining experiments. In addition, the measured machining outputs were forces, power consumption, flank wear, and surface roughness. There were no marks for the derivative cutting when using the textured cutting tool with the narrowest micro-grooves according to the obtained microscopical images after the machining tests. In addition, the textured cutting tool, which included the narrowest micro-grooves, showed better performance compared to the non-textured cutting tool and the other textured tool designs in terms of cutting and feed forces, power consumption, flank tool wear, and surface roughness at the used cutting conditions. This confirmed that the careful optimal design of the micro-textured tools can reduce or eliminate the severity of the derivative cutting, and thus improve the overall machining performance.

Effect of Groove Structure on Lubrication Performance of Water-Lubricated Stern Tube Bearings

This study investigated the lubrication characteristics (i.e., the groove ratio and width) of water-lubricated stern tube bearings, based on the flexibility matrix method and lubrication theory. Considering the elastic deformation of the lining, a fluid structure interaction (FSI) model of the surface micro-groove texture of a water-lubricated stern tube bearing was established, and the correctness and rationality of the model were verified by experiments. Micro-grooved, surface-lubricated, water-lubricated stern tube bearings with three different cross-sectional shapes (rectangular, circular, and triangular) were designed. The influences of the groove area ratio and width on the bearing load-carrying capacity and friction coefficient were analyzed. At a groove area ratio of 0.31, the load-carrying capacity of the rectangular grooved stern tube bearing reached the maximum value and the friction coefficient reached the minimum value. It is recommended to design and use water-lubricated stern tube bearings, especially Thordon water-lubricated stern tube bearings, with rectangular micro-grooves, with a groove area ratio of 0.30–0.32, so that the best lubrication performance can be obtained. With the increase in the micro-groove width, the lubrication of water-lubricated stern tube bearings with partial rectangular micro-grooves is significantly better than that of others. Under the same conditions, the bearing load-carrying capacity and friction performance of local groove stern bearings is significantly better than that of global groove stern bearings.

Experimental investigation of ns pulse laser processing parameters for machining of Ti-6Al-4V alloy

Traditional machining faces technical barriers in producing microfeatures when the workpiece poses high-strength and temperature-resistance characteristics. Laser is a possible machining approach that works effectively in the aforementioned conditions. The present study utilized a low-power fiber laser system machining of the Ti-6Al-4V alloy surface. The influence of laser processing parameters, for example average power, scanning speed, and pulse frequency, were analyzed on the laser-machined microgroove profiles using the full factorial design of the experiment. The results revealed that the fabricated microgroove profile characteristics, that is, depth, width, heat-affected zone (HAZ), surface roughness, etc. of laser-processed zone strongly depend on the laser processing parameters. Furthermore, the laser microgroove size, that is, depth and width, increases with the increment in laser power combined with low scan speed and low frequency. High laser power (50 W), low scan speed (0.1 mm/s), and low frequency (50 kHz) produce a microgroove with high depth (754.28 µm) and width (285.71 µm). It has been also observed that average power has the most significant impact on the machined surface profile, HAZ, and surface roughness. Moreover, it has also been observed that crack forms at the center of the machined surface is by decreasing scanning speed. Further, lower surface roughness is found at the highest pulse frequency. Hence, the present study recommends laser processing at lower power, high scanning speed, and high pulse frequency to generate a smooth and uniform machined surface.

Graphene Hollow Micropatterns via Capillarity-Driven Assembly for Drug Storage and Neural Cell Alignment.

Electrical conductivity, cell-guided surface topology, and drug storage capacity of biomaterials are attractive properties for the repair and regeneration of anisotropic tissues with electrical sensitivity, such as nerves. However, designing and fabricating implantable biomaterials with all these functions remain challenging. Herein, we developed a freestanding graphene substrate with micropatterned surfaces by a simple templating method. Importantly, the raised surface micropatterns had an internal hollow structure. The morphology results showed that the template microgroove width and the graphene nanosheet size were important indicators of the formation of the hollow structures. Through real-time monitoring and theoretical analysis of the formation process, it was found that the main formation mechanism was the delamination and interlayer movement of the graphene nanosheets triggered by the evaporation-induced capillary force. Finally, we achieved the controlled release of loaded microparticles and promoted the orientation of rat dorsal root ganglion neurons by applying an electric field to the hollow micropatterns. This capillarity-induced self-assembly strategy paves the way for the development of high-performance graphene micropatterned films with a hollow structure that have potential for clinical application in the repair of nerve injury.

Surface microstructure evolution of Cf/SiC ceramic matrix composite microgrooves processed by ultrafast laser

Modern aviation components have higher requirements for high temperature resistance, high strength and lightweight materials, and ceramic matrix composites have superior overall performance. However, its high brittleness and anisotropy lead to a challenge for manufacturing. In order to understand the formation conditions and the evolution of surface microstructures of the Cf/SiC microgrooves processed by ultrafast laser comprehensively, we designed a single-factor experiment and performed sensitivity analysis. The experiment results showed that the pulse energy had great effects on the depth of the microgroove, and the intense ablation caused more active oxidation of SiC to occur, generating more SiO(g). However, too much pulse energy may cause the material removal mechanism to be more due to the photothermal effect rather than the plasma effect. Low repetition frequency caused a large number of laminated connections in the microgroove and the oxide gradually changed from lumpy to flocculent as the repetition frequency increased. The more scanning times, the more ablation products sputtered onto the sample surface, including unablated carbon fibers. Shallow depth and ablation residues remained in the microgroove occurred under few scanning times. Although too fast scanning speed leaded to a rapid decrease in the microgroove depth, too slow scanning speed also generated more unablated carbon fibers sputtering out of the microgrooves. The microgroove depth had the highest sensitivity to the repetition frequency, followed by the pulse energy and scanning speed. The pulse energy and scanning speed had a greater effect on the oxide layer height, the repetition frequency affected the oxide layer width, and the scanning speed affected the microgroove width significantly. According to the processing requirements and the hot spot map, the processing parameters that can be adjusted effectively will be able to be obtained.

Scaling of Anisotropic Wetting Behavior of Water Drop Configuration Arising from Parallel Groove-Textured Stainless Steel Surfaces

Understanding the wetting behavior of stainless steel surfaces can help in resolving many socio-economic challenges faced by modern day engineering developments. In this research paper, investigations have been carried out to understand the role of surface unidirectional microgrooves on the wetting behavior by the water drop liquid using the liquid drop shape configuration, captured in the view direction parallel and orthogonal to surface microgrooves. Because of the variation in wetting characteristics between these two directions, i.e., anisotropic wetting behavior, the liquid drop has attained ellipsoidal shape configuration in the microgroove-textured stainless steel surfaces. Detailed investigation has been carried out in understanding the role of microgroove geometrical sizes, i.e., width and depth and the spacing between the grooves on the wetting behavior in terms of contact diameter (D) and contact angle (θ). Overall, the wetting dynamics has been characterized by looking at the variation of eccentricity (ε, as a ratio between D in the direction parallel to microgroove and the spreading diameter in the direction orthogonal to microgroove) and wetting anisotropy (Δθ, as a difference in θ between the direction orthogonal and parallel to microgroove) with the microgroove depth parameter (ϕ as a ratio between the microgroove depth and width) and the groove spacing parameter (ξ as a ratio of the spacing between the grooves and the groove width). By and large, with increase in surface non-dimensional geometrical parameters, ϕ and ξ, the parameters quantifying eccentricity, ε and Δθ decrease, so the liquid drop shape configuration shifts towards spherical cap from ellipsoidal cap.

Modeling and optimizing femtosecond laser process parameters for high-efficient and near damage-free micromachining of single-crystal GaN substrate

This paper presents a high-efficient and near damage-free micromachining method for gallium nitride (GaN) using femtosecond laser direct writing. To provide a precise selection principle of process parameters, the influences and interactions on GaN processing of parameters are systematically studied. Variance analysis results of single factor experiments show that laser power, scan speed, scan times and repetition frequency mainly influence the microgroove depth, microgroove width, heat-affected zone (HAZ) and material removal rate (MRR). In addition, the response surface method (RSM) indicates the interaction between scan times and repetition frequency has an appreciable influence on HAZ. And the interaction between scan speed and laser power plays a key role in MRR. Quadratic polynomial prediction models have been established by RSM and have discrepancies of less than 9.5% compared with the experimental results. The optimized parameters are important to achieve the desired control and high efficiency of femtosecond laser micromachining of single-crystal GaN substrate.

Enhanced Biotribological and Anticorrosion Properties and Bioactivity of Ti6Al4V Alloys with Laser Texturing.

The poor biotribological properties and bioinertness of Ti6Al4V have restricted its application in biomedical materials. In this study, microgrooves of different widths were prepared on the surface of a Ti6Al4V alloy by laser treatment. The tribological properties under dry lubrication and simulated body fluid (SBF) lubrication conditions, the electrochemical corrosion properties in SBF solution, and the bone marrow mesenchymal stem cell (BMSC) behavior on the surfaces were systematically tested. The corresponding mechanisms were discussed. The results showed that Ti6Al4V with a microgroove width of 45 μm (Ti64-45) exhibited excellent wear resistance with decreasing wear rates of 89.79 and 85.43% under dry friction and SBF lubrication compared to the Ti64 sample, which might be due to the increase of surface microhardness. Moreover, the excellent anticorrosion performance of Ti64-45 was attributed to the grain refinement on the titanium alloy surface with a lower volume fraction ratio of β phase to α phase. In addition, the microgrooves with a width of 45 μm are more conducive to BMSC proliferation and adhesion, related to promoting cell signal transduction due to cell extrusion. These studies imply that the microgroove structures are potential for application in the medical field.

The influence of laser surface texture on the tribological properties of friction layer materials in ultrasound motors

Ultrasonic motors are typically driven by the dry friction force between the rotor and the stator; the friction pairs’ high friction coefficient and low wear rate are two essential elements for improving the operational stability with longer service life. In this research article, high-precision microgroove arrays were manufactured on the surfaces of the stator and rotor of the TRUSM60 ultrasonic motor using laser machining. Dry friction and wear tests between the stator and the rotor were carried out with pin-on-disc using HSR-2M high-speed reciprocating friction and wear tester to determine the tribological properties of the ultrasonic motor. According to a different distribution of microgrooves on the two contact surfaces, the influence of smooth surface, single-sided texture, and double-sided texture on the friction pair's friction performance were discussed. The results show that the textured surface can substantially increase the coefficient of friction of the contact surface and reduce the rate of wear. The one-sided textured phosphor bronze surface with a microgroove width of 200μm and an area ratio of 20% had the highest coefficient of friction of 0.334 and a friction increase rate of 36.3%. Similarly, the single-sided textured Polyimide surface attained the highest friction coefficient of 0.355 and friction increase rate of 44.9% when the groove width is 150μm and the area ratio is 30%. A higher friction coefficient of the double-sided texture can be obtained through reasonable parameter configuration than the single-sided texture. The included angle of 0° between the two textured surfaces produced the highest friction coefficient of 0.368 and the wear rate of the phosphor bronze and polyimide surfaces were 2.01 × 10−4 mm3/N-m and 1.949 × 10−3 mm3/N-m, respectively. The result provides an essential benchmark for enhancing the tribological performance of ultrasonic motors and increasing the output torque.

Effect of surface micro-groove texture on lubrication performance of tripod universal coupling

Purpose This study aims to study the effect of micro-groove texture geometric parameters on the lubrication characteristics of the tripod universal coupling. Design/methodology/approach The Navier–Stokes equation was used to analyse the influence of micro-groove geometric parameters on the coupling’s lubrication performance. Further, Kriging approximate model and neighborhood cultivation genetic algorithm (NCGA) were used to optimise the micro-groove geometric parameters and improve the coupling’s lubrication performance. Findings The results show that as the micro-groove depth and width increase, respectively, the oil film-bearing capacity first increases and then decreases; on the contrary, the friction coefficient first decreases and then increases. With the increase of the micro-groove inclination angle, the bearing capacity of the oil film first increases and then remains unchanged. At the same time, the friction coefficient first decreases and then increases slightly. The lubricating performance of the optimised coupling is significantly improved: the optimised oil film-bearing capacity increases by 12.5%, the friction coefficient reduces by 14% and the maximum oil film pressure increases by 4.3%. Originality/value At present, the grease lubrication performance of the micro-groove textured tripod universal coupling has not been studied. The micro-groove parameters are optimised, and the coupling’s lubrication performance is improved greatly by the Kriging model and NCGA algorithm. It is of great significance to extend the coupling’s fatigue life.

The FDTD Analysis of Near-Field Response for Microgroove Structure With Standing Wave Illumination for the Realization of Coherent Structured Illumination Microscopy

Abstract Microstructures are widely used in the manufacture of functional surfaces. An optical-based super-resolution, non-invasive method is preferred for the inspection of surfaces with massive microstructures. The structured illumination microscopy (SIM) uses standing-wave illumination to reach optical super-resolution. Recently, coherent SIM is being studied. It can obtain not only the super-resolved intensity distribution but also the phase and amplitude distribution of the sample surface beyond the diffraction limit. By analysis of the phase-depth dependency, the depth measurement for microgroove structures with coherent SIM is expected. FDTD analysis is applied for observing the near-field response of microgroove under the standing-wave illumination. The near-field phase shows depth dependency in this analysis. Moreover, the effects from microgroove width, the incident angle, and the relative position between the standing-wave peak and center of the microgroove are investigated. It is found the near-field phase change can measure depth until 200 nm (aspect ratio 1) with an error of up to 20.4 nm in the case that the microgroove width is smaller than half of the wavelength.

Comparison of nanofluid wetting characteristics in untreated and superhydrophilic microgrooved heat pipes

The thermal performance of the microgrooved heat pipes is mainly restricted by the wick capillary limit. The construction of micro-nano structures and using nanofluids are effective ways to improve the microgroove wetting characteristic and heat transfer ability. Based on the accommodation theory, a model for nanofluid wetting characteristics in the microgrooved heat pipe was presented in this paper. The axial wetting ability of SiO2 nanofluid in untreated rectangular microgrooves (RMs) and rectangular microgrooves with superhydrophilic nano-textured surfaces (RMSNSs) were compared. The results indicate that the total wetting length (Lt) of SiO2 nanofluids in RMSNSs was remarkably longer than that in RMs. For RMs, the wetting length in the corner flow region (Lc) could nearly be ignored. However, Lc of RMSNSs increased significantly being about 35% of Lt. When the nanoparticle size rose from 15 to 50 nm, Lt of RMSNSs increased by about 13% but that of RMs decreased slightly. When the heat flux increased from 0 to 120 kW/m2, Lt of RMSNSs and RMs dropped by about 72.6% and 69.5% respectively due to the liquid evaporation. Also, the microgroove depth and width had remarkable effects on the wetting length and the optimal depth to width ratio was about 2:1.

Effect of micro grooves on lubrication performance of friction pairs

The influence of micro-groove parameters on the lubrication performance of plane friction pair is studied, by combining theoretical analysis with experiment. The theoretical model of single-groove is established, the variation rules of bearing capacity, maximum pressure and friction coefficient are obtained by changing the number, width and depth of groove. At the same time, micro-grooves with different parameters are processed on the surface of friction pair, the variation rules of the average friction coefficient, friction coefficient under different lubrication conditions are obtained in experiment, and the wear condition of friction pair surface is observed. The results show that the lubrication performance of friction pair increases, with the increase of the micro-groove width. The numerical value of the groove width–depth ratio will influence the friction pair, when the width–depth ratio is greater than or equal to 2.5, the dynamic pressure effect of micro-groove occupies a dominant position, which can improve effectively the lubrication performance. When the width–depth ratio is less than 2.5, the micro-groove will have a negative impact, resulting in the increase of friction coefficient. The groove density will also influence the lubrication performance of friction pair, when the density is less than 10%, the spacing between the micro grooves is too large to collect wear particles, when the density is greater than 20%, the surface roughness of friction pair will be affected, leading to the increase of friction coefficient. The optimal parameters of the micro-groove obtained are as follows: the optimal density is 10%, the width is 0.1–0.2 mm, and the ratio of width to depth is greater than or equal to 2.5. In addition, by comparing the variation of friction coefficient under different lubrication conditions, it can be concluded that adding solid lubricant in lubricating oil, can not only reduce the friction coefficient value, but also decrease the variation fluctuation of friction coefficient.

4D Printed Cardiac Construct with Aligned Myofibers and Adjustable Curvature for Myocardial Regeneration.

As an innovative additive manufacturing process, 4D printing can be utilized to generate predesigned, self-assembly structures which can actuate time-dependent, and dynamic shape-changes. Compared to other manufacturing techniques used for tissue engineering purposes, 4D printing has the advantage of being able to fabricate reprogrammable dynamic tissue constructs that can promote uniform cellular growth and distribution. For this study, a digital light processing (DLP)-based printing technique was developed to fabricate 4D near-infrared (NIR) light-sensitive cardiac constructs with highly aligned microstructure and adjustable curvature. As the curvature of the heart is varied across its surface, the 4D cardiac constructs can change their shape on-demand to mimic and recreate the curved topology of myocardial tissue for seamless integration. To mimic the aligned structure of the human myocardium and to achieve the 4D shape change, a NIR light-sensitive 4D ink material, consisting of a shape memory polymer and graphene, was created to fabricate microgroove arrays with different widths. The results of our study illustrate that our innovative NIR-responsive 4D constructs exhibit the capacity to actuate a dynamic and remotely controllable spatiotemporal transformation. Furthermore, the optimal microgroove width was discovered via culturing human induced pluripotent stem cell-derived cardiomyocytes and mesenchymal stem cells onto the constructs' surface and analyzing both their cellular morphology and alignment. The cell proliferation profiles and differentiation of tricultured human-induced pluripotent stem cell-derived cardiomyocytes, mesenchymal stem cells, and endothelial cells, on the printed constructs, were also studied using a Cell Counting Kit-8 and immunostaining. Our results demonstrate a uniform distribution of aligned cells and excellent myocardial maturation on our 4D curved cardiac constructs. This study not only provides an efficient method for manufacturing curved tissue architectures with uniform cell distributions, but also extends the potential applications of 4D printing for tissue regeneration.

Magnetically Controllable Isotropic/Anisotropic Slippery Surface for Flexible Droplet Manipulation.

Controllable wetting surfaces play a significant role in numerous applications such as smart liquid manipulation, lab-on-a-chip, drug delivery, liquid robot, and so on. A novel type of magnetically controllable isotropic/anisotropic slippery surface was prepared by femtosecond laser ablation. The slippery liquid-infused porous surface (SLIPS) can be switched between an isotropic smooth state and an anisotropic groove state by the magnetic field. The relationship between the sliding property of the SLIPS and the magnetic flux density, water droplet volume, microgroove width, and microgroove height are systematically studied. Passively flexible movement on the isotropic SLIPS and actively directional movement on the anisotropic SLIPS of water droplets were realized. This work provides a fresh understanding of the controllable isotropic/anisotropic SLIPS and reveals great potential in versatile applications which are related to magnetically controllable smart liquid manipulation.

Enhanced anticorrosion and antiwear properties of Ti–6Al–4V alloys with laser texture and graphene oxide coatings

The poor antiwear properties of Ti–6Al–4V have restricted its applications as biomedical materials. In this work, microgrooves with different groove width and graphene oxide (GO) coating were constructed on the surface of Ti–6Al–4V by laser processing and chemical assembly, respectively. The effects of microgroove width on the anticorrosion and biotribological properties of GOs-coated Ti–6Al–4V alloys were systematically investigated. The results indicate that the GOs-coated sample with 45 μm groove width (Ti-45-GO) can effectively improve the anticorrosion of Ti–6Al–4V, due to the surface microstructure homogenization from Ti−45 substrate and the shielding effect of GO coatings. Furthermore, the Ti-45-GO sample exhibits excellent antiwear properties, owing to the capture of wear debris of microgrooves and the high strength and resilience from GO coatings.

Effect of substrate topography on the regulation of human corneal stromal cells

Optimal functionality of native corneal stroma depends on a well-ordered arrangement of extracellular matrix (ECM). To develop an in vitro corneal model, replication of the corneal in vivo microenvironment is needed. In this study, the impact of topographic cues on keratocyte phenotype is reported. Photolithography and polymer moulding were used to fabricate microgrooves on polydimethylsiloxane (PDMS) 2–2.5 μm deep and 5 μm, 10 μm, or 20 μm in width. Microgrooves constrained the cells body, compressed nuclei and led to cytoskeletal reorganization. It also influenced the concentration of actin filaments, condensation of chromatin and cell proliferation. Cells became more spread and actin filament concentration decreased as the microgroove width increased. Relationships were also demonstrated between microgroove width and cellular processes such as adhesion, migration and gene expression. Immunocytochemistry and gene expression (RT-PCR) analysis showed that microgroove width upregulated keratocyte specific genes. A microgroove with 5 μm width led to a pronounced alignment of cells along the edges of the microchannels and better supported cell polarization and migration compared with other microgroove widths or planar substrates. These findings provide important fundamental knowledge that could serve as a basis for better-controlled tissue growth and cell-engineering applications for corneal stroma regeneration through topographical patterns.