Influence of 3D Microgrooves on C2C12 Cell Proliferation,Migration,Alignment,F-actin Protein Expression and Gene Expression

In this paper, we fabricated three kinds of 3D microgrooves with different depth on biocompatible poly（lactic-co-glycolic acid） （PLGA） substrate via combination of soft-lithography and melt-casting methods, and investigated in detail their influence on C2C12 cell behaviors. It is found that cell proliferation, migration, alignment, spatial distribution, F-actin protein expression and gene expression are all remarkably distinct on these microgrooved samples and the smooth control PLGA substrate. The associated underlying mechanisms were further analyzed and discussed using real-time living cell monitoring, confocal laser scanning microscopy and gene microarray. Our preliminary results suggested that 3D microstruc- ture could affect cell behaviors in a much more extensive manner than what we had understood before.

FEM analysis of workpiece curvature influence on groove deformation during plough process

To investigate the workpiece curvature influence on groove deformation,numerical studies with curvature varying from negative to positive were conducted on copper material.Groove deformations were analyzed,including groove geometry,effective stress distribution and plough force.The curled groove shape whose workpiece curvature was 0.133 mm-1 was validated by experiments.Moreover,a series of geometry models with various curvatures were introduced to analyze the change of groove deformation.The results show that positive curvatures influence groove deformation more intensively than negative or zero curvature.It is mainly due to the action of the tool forming face during plough process.

Heat transfer performance testing of a new type of phase change heat sink for high power light emitting diode

In view of the limitations of solid metal heat sink in the heat dissipation of high power light emitting diode （LED）, a kind of miniaturized phase change heat sink is developed for high power LED packaging. First, the fabrication process of miniaturized phase change heat sink is investigated, upon which all parts of the heat sink are fabricated including main-body and end-cover of the heat sink, the formation of three-dimensional boiling structures at the evaporation end, the sintering of the wick, and the encapsulation of high power LED phase change heat sink. Subsequently, with the assistance of the developed testing system, heat transfer performance of the heat sink is tested under the condition of natural convection, upon which the influence of thermal load and working medium on the heat transfer performance is investigated. Finally, the heat transfer performance of the developed miniaturized phase change heat sink is compared with that of metal solid heat sink. Results show that the developed miniaturized phase change heat sink presents much better heat transfer performance over traditional metal solid heat sink, and is suitable for the packaging of high power LED.

Mechanisms of rectangular groove-induced multiple-microdroplet coalescences

The mechanism of microdroplet coalescence is a fundamental issue for droplet-based microfluidics. We developed an asymmetric expansion (a rectangular groove) along one side of a microchannel to achieve multiple-microdroplet trapping, collision, and coalescence. Compared with reported symmetric expansions, this asymmetric groove could easily trap microdroplets and control two or three microdroplet coalescences precisely without a requirement for temporal and spatial synchronization. To reveal the mechanisms of multiple-droplet coalescences in a groove, we observed five different coalescence patterns under different flow conditions. Moreover, we characterized the flow behavior quantitatively by simulating the velocity vector fields in both the microdroplets and continuous phase, finding good agreement with experiments. Finally, a map of coalescence forms with different capillary numbers () and flow ratios () was obtained. The results could provide a useful guidance for the design and application of droplet-based microfluidic devices.

Optimization of three-dimensional boiling enhancement structure at evaporation surface for high power light emitting diode

A theoretical model of phase change heat sink was established in terms of thermal resistance network. The influence of different parameters on the thermal resistance was analyzed and the crucial impact factors were determined. Subsequently, the forming methods including ploughing-extrusion and stamping method of boiling enhancement structure at evaporation surface were investigated, upon which three-dimensional microgroove structure was fabricated to improve the efficiency of evaporation. Moreover, the crucial parameters related to the fabrication of miniaturized phase change heat sink were optimized. The heat transfer performance of the heat sink was tested. Results show that the developed phase change heat sink has excellent heat transfer performance and is suitable for high power LED applications.

Microtopography Attenuates Endothelial Cell Proliferation by Regulating MicroRNAs

Endothelial cell (EC) morphology can be regulated by the micro/nano topography in engineered vascular grafts and by hemodynamic forces in the native blood vessels. However, how EC morphology affects miRNA and thus EC functions is not well understood. In this study, we addressed this question by using human umbilical vein endothelial cells (HUVECs) cultured on microgrooves as a model. HUVECs were grown on either microgrooved (with 10 μm width/spacing and 3 μm depth) or smooth surfaces. HUVECs on microgrooved surface had elongated and bipolar morphology, while HUVECs on smooth surface showed cobble stone shape or non-polar morphology. EdU staining indicated that HUVECs with elongated morphology had lower proliferation rate compared to their counterpart cultured on smooth surface. Quantitative PCR analysis demonstrated that the expression of the specific microRNAs (miR-10a, miR-19a, miR-221) that targeted proliferation-related genes was all up-regulated. Consistently, the mRNA levels of their respective target genes, mitogen-activated protein kinase kinase kinase 7, Cyclin D1 and c-kit were significantly reduced by a fold change of 0.12 ± 0.01 (p < 0.01), 0.70 ± 0.23 (p 0.05) and 0.76 ± 0.21 (p < 0.05). Other miRNAs such as miR-126 and miR-181a were up-regulated as well, leading to the repression of their targets vascular cell adhesion molecule-1 and prospero homeobox-1. Our results suggested that microgrooved surface may regulate microRNA levels and thus EC functions. These results provide insight into the modulation of EC functions by microtopographic cues, and will facilitate the rational design of microstructured materials for cell and tissue engineering.

Numerical analysis on mixed lubrication performance of journal-thrust coupled microgroove bearings with different bottom shapes

The purpose of the present study is to establish a mixed lubrication model for the journal-thrust coupled microgroove bearings(also referred as coupled bearings)used for the ship shaftless rim-driven thrusters.During the hydrodynamic modelling,the coupling hydrodynamic pressure between the journal bearing and the thrust bearing is considered.The mixed lubrication performances of the microgroove journal-thrust bearing with five different bottom shapes,including rectangle,semi-ellipse,right triangle,isosceles triangle and left triangle,are compared.Based on the numerical results,the optimal microgroove bottom shape of the journal bearing and tilting angle of the thrust pad are determined.Additionally,the comparative analysis shows that the coupled bearing with left triangle microgroove bottom shape exhibits the optimal mixed lubrication performance.The numerical result also indicates that the optimal inclination angle of the thrust bearing pad is 0.01°for the current simulation case.

Performance Analysis of the Effects of Microgrooved Surface on A Marine Current Turbine with Underwater Mooring Platform

Marine current turbine(MCT),which is designed for the power supply of underwater mooring platform(UMP),is investigated in this article.To reduce its flow noise,the microgrooved surface is applied at the suction surface of the turbine blades.Comprehensive analyses of the effects of the UMP on MCT with microgrooved surface in different working conditions are presented.The transient turbulent flow field is obtained by incompressible large eddy simulation(LES),and then the Ffowcs Williams and Hawkings(FW-H)acoustic analogy is adopted to forecast the flow noise generated from the pressure fluctuations and loadings of the UMP shell and MCT blade surfaces.The numerical methods are first validated with experimental data and good agreements are obtained.Then,the influence of several key parameters on the performance of the MCT is then systematically studied,including interval distance,angle of pitch and angle of sideslip.For each case,the hydrodynamic parameters(thrust coefficient,torque coefficient and power coefficient),the vortical structures behind the model and the overall sound pressure level(OASPL)directionality are analyzed.Additionally,the noise reduction effect of the microgrooved surface is also presented.The present investigation could provide an overall understanding for the performance of MCT combined with UMP.

Cell Morphology Modified by Biomaterial Induces miR-21 Expression and Apoptosis

Biochemical factors can play an important role in regulating gene expression in human umbilical vein endothelial cells (HUVECs), yet the role of biophysical factors during this process is unknown. Here, we show that physical cues, in the form of parallel microgrooves on the surface of cell adhesive substrates, can change the morphology of HUVECs as well as specific microRNA expression. Cells cultured on microgrooved poly (dimethyl siloxane) (PDMS) surface exhibited a more elongated morphology relative to those cultured on flat surfaces, and favored outgrowth along the axis of groove alignment. The level of microRNAs in the cell was screened by miRNA microchip and verified by qRT-PCR. The result showed that around 26 microRNAs have been modified significantly, among which miR-21 level was dramatically elevated. Western-blotting analysis demonstrated that PTEN, a target of miR- 21, was up-regulated in HUVECs with elongated morphology. Cell apoptosis level was significantly decreased, with was associated with the increasing of miR-21 level. These results suggested that biophysical factors can directly modify HUVECs morphology, thus induce miR-21 expression in HUVECs and its downstream biological functions such as decreasing apoptosis. This study provided evidence that surface microtopology should also be considered in designing biomaterials in tissue engineering application.

A novel micro-rolling&incremental sheet forming hybrid process:Deformation behavior and microstructure evolution

Thin-walled metal parts with functional micro-featured surface have broad application prospects in the fields of resistance reduction,noise reduction,etc.In this study,a novel micro-rolling&incremental sheet forming hybrid process(μR-ISF)is proposed to fabricate thin-walled metal parts with microgroove arrays.An analytical model which relates the rolling force and microgroove depth in the micro-rolling stage was first established.Then,the formation mechanism of microgroove morphology during both micro-rolling stage and macro-shape forming stage are investigated.After the micro-grooved sheet being incrementally formed,a significant reduction(between 21%to nearly 60%)is occurred in the depth of both transverse and longitudinal grooves compared to the flat sheet.Meanwhile,the width of transverse grooves decreases slightly by about 10%on average,while the width of longitudinal microgrooves increases significantly by more than 30%on average.After micro-rolling,85°{102}tensile twins appear on the micro-grooved sheet and the percentage of 65°{112}compressive twins increases.After incremental forming,the percentage of low-angle grain boundaries and the density of geometrically necessary dislocations in the formed part increase significantly,and the grain size distribution becomes more uniform.The present work provides a new strategy for the fabrication of 3D metal thin-walled components with surface micro-features.

Soft nanofiber modified micropatterned substrates enhance nativelike endothelium maturation via CXCR4/calcium-mediated actin cytoskeleton assembly

Regeneration and maturation of native-like endothelium is crucial for material-guided small-diameter vascular regeneration.Although parallel-microgroove-patterned(micropatterned)substrates are capable of promoting endothelial regeneration with native-like endothelial cell(EC)alignment,their unbefitting high-stiffness acutely inhibits cell–matrix interaction and endothelial maturation.Given that the sufficient softness of nanofibers allows cells to deform the local matrix architecture to satisfy cell survival and functional requirements,in this study,an effective strategy of decorating micropatterned substrate with soft nanofibers was exploited to enhance cell–matrix interaction for engineering healthy endothelium.Results demonstrated that the micropatterned nanofibrous membranes were successfully obtained with high-resolution parallel microgrooves(groove width:~15μm;groove depth:~5μm)and adequate softness(bulk modulus:2.27±0.18 MPa).This particular substrate markedly accelerated the formation and maturation of confluent native-like endothelium by synchronously increasing cell–cell and cell–matrix interactions.Transcriptome analysis revealed that compared with smooth features,the microgrooved pattern was likely to promote endothelial remodeling via integrinα5-mediated microtubule disassembly and type I interleukin 1 receptormediated signaling pathways,whereas the nanofibrous pattern was likely to guide endothelial regeneration via integrinα5β8-guided actin cytoskeleton remodeling.Nevertheless,endowing micropatterned substrate with soft nanofibers was demonstrated to accelerate endothelial maturation via chemokine(C-X-C motif)receptor 4/calcium-mediated actin cytoskeleton assembly.Furthermore,numerical simulation results of hemodynamics indicated the positive impact of the micropatterned nanofibers on maintaining stable hemodynamics.Summarily,our current work supports an affirmation that the micropatterned nanofibrous substrates can significantly promote regeneration and maturation of native-like endothelium,which provides an innovative method for constructing vascular grafts with functional endothelium.

Electrochemical micromachining of microgroove arrays on phosphor bronze surface for improving the tribological performance

A high friction coefficient and a low wear rate of contacted surfaces are essential elements to friction pairs between the stator and the rotor in ultrasonic motors. It has been shown that surface textures have a significant effect on improving the tribological performance of friction pairs.In this paper, microgroove arrays are introduced to the stator surface for improving the tribological performance of friction pairs between the stator and the rotor in ultrasonic motors. Microgrooves were fabricated on a phosphor bronze surface by through-mask electrochemical micromachining（TMEMM）. Parameters, namely, the electrolyte inlet pressure, applied voltage, pulse duty cycle,and frequency, were varied to investigate their influences on the dimensions and morphology of the microgrooves. Results showed that the width and depth of the microgrooves were strongly affected by the applied voltage and frequency, while the morphology of the microgrooves was dependent on the electrolyte inlet pressure and the pulse duty cycle. Compared with a smooth surface, the friction coefficient increased from 0.245 to 0.334 and less abrasion was obtained when a surface was textured with microgrooves of which the width and depth were 185.6 and 57.6 lm,respectively. Microgroove arrays might play an important role in enhancing the performance of ultrasonic motors.

Laser-induced oxidation assisted micro milling of high aspect ratio microgroove on WC-Co cemented carbide

Severe tool wear and poor surface quality are the main problems during micro machining of cemented carbide.In this work,an innovative hybrid process of laser-induced oxidation assisted micro milling(LOMM)was proposed to solve the problems.A nanosecond laser was utilized to induce oxidation of the WC-20%Co material,producing loose oxide which was easy to remove.The micro machinability of the material was improved by laser-induced oxidation.The oxidation mechanisms of cemented carbide were studied.A microgroove with a depth of 2.5 mm and aspect ratio of 5 was fabricated successfully.The milling force,surface quality and tool wear mechanisms were investigated.For comparison,a microgroove was also fabricated with conventional micro milling(COMM)using identical milling parameters.Results revealed that in LOMM the milling force and tool wear rate were extremely low during removing the oxide.The machined surface quality and dimensional accuracy achieved by LOMM were superior to those obtained by COMM.The surface roughness Saof the microgroove bottom reached 88 nm in LOMM,while the cross-sectional geometry of the microgroove was a trapezoid.Perpendicularity of the microgroove sidewall machined by LOMM was better than that by COMM.The tool wear forms in LOMM were coating spalling and slight tool nose breakage.Compared with COMM,the tool life in LOMM was prolonged significantly.It indicates that the proposed hybrid process is an effective and efficient way to fabricate high aspect ratio micro-features with high dimensional accuracy.

Recent advancements in optical microstructure fabrication through glass molding process

Optical microstructures are increasingly applied in several fields, such as optical systems, precision measurement, and microfluid chips. Microstructures include microgrooves, microprisms, and microlenses. This paper presents an overview of optical microstructure fabrication through glass molding and highlights the applications of optical microstructures in mold fabrication and glass molding. The glass-mold interface friction and adhesion are also discussed. Moreover, the latest advance- ments in glass molding technologies are detailed, including new mold materials and their fabrication methods, viscoelastic constitutive modeling of glass, and micro- structure molding process, as well as ultrasonic vibration- assisted molding technology.

Effect of stagger angle on capillary performance of microgroove structures with reentrant cavities

Aluminum-based microgroove surfaces with reentrant cavities (MSRCs) were fabricated by two staggered ploughing/extrusion processes to meet the requirements of lightweight phase change heat transfer devices.Five MSRCs with different stagger angles between cavities and microgrooves (MGs) were fabricated to study the effect of stagger angle on capillary performance.Capillary rise and permeability tests were performed on all MSRCs and the results were compared with MGs having the same processing parameters.It was found that MSRCs with smaller stagger angles have higher capillary height,and the maximum enhancement maintained by MSRC45 was about 54.84%.However,MSRCs with larger stagger angles were found to have higher permeability.Therefore,the capillary parameter K·ΔP_(cap)was used as a comprehensive index to evaluate these wicks.MSRC90 and MSRC75 obtained the largest K·ΔP_(cap)values without and with the effect of gravity considered,respectively.Although all MSRCs had a higher capillary rise height than MGs,smaller stagger angles (≤60°) seriously reduced the permeability of MSRCs and even resulted in smaller K·ΔP_(cap)value than that of MGs when calculated considering the effect of gravity.Therefore,MSRCs with larger stagger angles (≥75°) may be the optimum wicks due to the good balance between capillary pressure and permeability.

Heat Transfer Performance of Microgroove Back Plate Heat Pipes with Working Fluid and Heating Power

Micro heat pipes(MHP) cooling is one of the most efficient solutions to radiate heat for high heat flux electronic components in data centers. It is necessary to improve heat transfer performance of microgroove back plate heat pipes. This paper discusses about influence on thermal resistance through experiments and numerical simulation with different working fluids, filling ratio and heat power. Thermal resistance of the CO2 filled heat pipe is 14.8% lower than the acetone filled heat pipe. In the meantime, at the best filling ratio of 40%, the CO2 filled heat pipe has the optimal heat transfer behavior with the smallest thermal resistance of 0.123 K/W. The thermal resistance continues to decline but the magnitude of decreases is going to be minor. In addition, this paper illustrates methods about how to enhance heat pipe performance from working fluids, filling ratio and heat power, which provides a theoretical basis for practical applications.

Algorithm of Micro-Grooving and Imaging Processing for the Generation of High-Resolution Structural Color Images

The use of submicron structures for structural coloration of surfaces has broad applications for color filters,projection displays,virtual reality,and anti-counterfeiting.Currently,structural color images lack high resolution due to low manufacturing accuracy.In this study,the axial-feed fly cutting(AFC)method is proposed to fabricate submicron grooves for the diffraction of visible light to create structural color images.We establish the relationship between the color information in the pixels of the original image and the parameters of the array units corresponding to the pixels.An algorithm to determine groove spacing and the tool path is established,and array units with the desired groove spacing are machined to reproduce the structural color images.The submicron grooves fabricated by AFC have high quality and good consistency.Due to the excellent diffraction performance of the machined grooves,images with high saturation and resolution can be reproduced.It is verified that images with various colors can be efficiently fabricated using the proposed method and algorithm.

Fabrication and boiling heat transfer characterization of multiscale microgroove surfaces

Microstructural functional surfaces play an important role in energy conversion applications including power generation,air conditioning,and thermal management of electronics through the boiling process.In this study,multi-scale microgroove surfaces were fabricated by the combination of wire electrical discharge machining(WEDM)and electrical discharge shaped machining(EDSM)to achieve a better boiling performance.The WEDM,with the advantage of high efficiency,was used to fabricate the first microgroove array,and rougher surfaces were formed by intense discharge.A wavy electrode was used in EDSM to fabricate the second microgroove array.Reentrant cavities at the intersections of microgrooves and rougher micro fins with spacing distribution were formed after EDSM.The boiling performance of the multi-scale microgroove surface was studied with water as the working medium under atmospheric pressure.The results indicated that the boiling performance of the microgroove surface is significantly enhanced.The critical heat flux and maximum heat transfer coefficient of microgroove surface were higher than the surfaces fabricated only by WEDM or EDSM,which were 2.34 and 3.29 times that of smooth copper plate,respectively.This study demonstrated that the combination of WEDM and EDSM is a convenient and effective method to fabricate high-performance microgroove boiling surfaces.