Microgrooved Surfaces Research Articles

Biocompatibility of Ti-6Al-4V titanium alloy implants with laser microgrooved surfaces

ABSTRACT The successful implantation depends on the favorable biocompatibility of the implant. In this paper,microgrooves on the surface of Ti-6Al-4V titanium alloy implants were made by laser processing technology,scanning electron microscopy and surface profilometer were used to observe the laser textured titanium samples,firstly. Then, the liquid-solid contact angle-measuring instrument was used to characterize the wettability of titanium samples. Finally,using a microplate reader and laser confocal microscope, the cytological behavior of cell proliferation, adhesion, differentiation, and cell morphology on the surface of different samples were studied.It showed that laser microgrooved surfaces had reduced liquid-solid contact angles,increased surface roughness,and better proliferation and differentiation of osteoblasts, while most cells grew along the microgrooves. These results indicate that the increased wettability provides a better growth environment for cell growth. Microgrooves are crucial in cell contact guidance, while their parameters control cell behavior and deserve an in-depth study.

Micro-grooved surface laser texturing of zirconia: Surface characterization and artificial soft tissue adhesion evaluation

Despite the reported high success of dental implants, problems related to biofilm formation and peri-implantitis due to the entrance and proliferation of bacteria on the peri-implant zone have increasing attention. In this sense, this work proposes a new zirconia surface with micro-grooves aiming to develop an effective tight seal between artificial soft tissue and implant surface and thus, to protect from bacterial invasion. In this study, different laser and design parameters were tested to produce successive micro-grooves with different and variated depth, width and wall. The micro-grooves were produced by a Nd:YAG laser and were morphologically characterized by SEM. Higher marked depths were obtained for a high number of laser passages under low scan speed as a result of a high amount of laser energy density. The most adequate conditions were mechanically tested regarding their capacity to retain artificial soft tissue (mimicking natural gingiva) by mechanical tensile strength test. The strength of adhesion between soft tissue and the micro-grooved surface revealed to be strongly dependent on the depth and width. The obtained results showed that the production of successive micro-grooves on the zirconia surface increased the adhesion of artificial soft tissue to its surface, proving that laser technology is a promising approach for the manufacturing of implants with micro-grooves sites that can protect from bacterial invasion.

Breaking Droplet Jumping Energy Conversion Limits with Superhydrophobic Microgrooves.

Coalescence-induced droplet jumping has the potential to enhance the performance of a variety of applications including condensation heat transfer, surface self-cleaning, anti-icing, and defrosting to name a few. Here, we study droplet jumping on hierarchical microgrooved and nanostructured smooth superhydrophobic surfaces. We show that the confined microgroove structures play a key role in tailoring droplet coalescence hydrodynamics, which in turn affects the droplet jumping velocity and energy conversion efficiency. We observed self-jumping of individual deformed droplets within microgrooves having maximum surface-to-kinetic energy conversion efficiency of 8%. Furthermore, various coalescence-induced jumping modes were observed on the hierarchical microgrooved superhydrophobic surface. The microgroove structure enabled high droplet jumping velocity (≈0.74U) and energy conversion efficiency (≈46%) by enabling the coalescence of deformed droplets in microgrooves with undeformed droplets on adjacent plateaus. The jumping velocity and energy conversion efficiency enhancements are 1.93× and 6.67× higher than traditional coalescence-induced droplet jumping on smooth superhydrophobic surfaces. This work not only demonstrates high droplet jumping velocity and energy conversion efficiency but also demonstrates the key role played by macroscale structures on coalescence hydrodynamics and elucidates a method to further control droplet jumping physics for a plethora of applications.

Biofunctionalization of Microgroove Surfaces with Antibacterial Nanocoatings.

Objectives To investigate the physical properties of the modified microgroove (MG) and antibacterial nanocoated surfaces. In addition, the biological interactions of the modified surfaces with human gingival fibroblasts (HGFs) and the antibacterial activity of the surfaces against Porphyromonas gingivalis were studied. Methods The titanium nitride (TiN) and silver (Ag) coatings were deposited onto the smooth and MG surfaces using magnetron sputtering. A smooth titanium surface (Ti-S) was used as the control. The physicochemical properties including surface morphology, roughness, and hydrophilicity were characterized using scanning electron microscopy, atomic force microscopy, and an optical contact angle analyzer. The “contact guidance” morphology was assessed using confocal laser scanning microscopy. Cell proliferation was analyzed using the Cell Counting Kit-8 assay. The expression level of the main focal adhesion-related structural protein vinculin was compared using quantitative reverse transcription PCR and Western blotting. The antibacterial activity against P. gingivalis was evaluated using the LIVE/DEAD BacLight™ Bacterial Viability Kit. Results The Ag and TiN antibacterial nanocoatings were successfully deposited onto the smooth and MG surfaces using magnetron sputtering technology. TiN coating on a grooved surface (TiN-MG) resulted in less nanoroughness and greater surface hydrophilicity than Ag coating on a smooth surface (Ag-S), which was more hydrophobic. Cell proliferation and expression of vinculin were higher on the TiN-MG surface than on the Ag-coated surfaces. Ag-coated surfaces showed the strongest antibacterial activity, followed by TiN-coated surfaces. Conclusion Nano-Ag coating resulted in good antimicrobial activity; however, the biocompatibility was questionable. TiN nanocoating on an MG surface showed antibacterial properties with an optimal biocompatibility and maintained the “contact guidance” effects for HGFs.

Effects of surface composite structure with micro-grooves and Sn-Ag-Cu on reducing friction and wear of Ni3Al alloys

To overcome the failure of liquid lubricants in the fields of energy equipment and aerospace industry, the synergistic effect of surface micro-textures and solid lubricants is a promising approach to solve the problem. This paper sought to improve the tribological performance by designing the surface composite structure on a Ni3Al metal matrix, in which surface micro-textures were filled by solid lubricants 96.5Sn-3.0Ag-0.5Cu alloys (SAC305). Dry reciprocating sliding tests were conducted as a basic assessment for synergistic lubricating analysis of surface composite structure. Results showed that the composite structure with the surface texture density of 28% and deposited SAC305 alloys had the lowest friction coefficient (0.39) and mean wear volume (0.37mm3) in comparison with other prepared samples. The reasons of the surface composite structure reducing the friction and wear of Ni3Al alloys mainly are that SAC305 alloys deposited into surface micro-grooves can improve the capacities of load-carrying and resistance to plastic deformation of the contact surface, and a SAC305 lubricating film formed on contact interface can reduce the direct contact between the counterpart ball and Ni3Al matrix. The Ni3Sn2 phase generated at the interface under the roles of friction behavior, which acts as a transiting layer to connect Ni3Al matrix and SAC305 alloys, promotes the formation of the self-adaptive friction structure. Moreover, the interconnection between the dynamic change of the friction coefficient and a lubricating film formed on contact interface was established, which could be used to evaluate the wear characteristics applied in the engineering field under harsh conditions.

미세 홈 구조 폴리머 표면의 발수성과 비등방 젖음성

미세 홈 구조 폴리머 표면의 발수성과 비등방 젖음성

Analysis of vascular smooth muscle cell and HeLa cell migration on the microgrooved substrate (Cell type differences of the mechanical sensing for microgrooved surfaces)

Cell migration is critical in many physiological processes, including morphogenesis, wound healing, and metastasis of cancer cells, and thus elucidation of the mechanism of cell migration is quite important. It is well known that these processes of cell migration can be guided by microenvironment of the substrate surfaces, such as microgrooves. However, detailed mechanism of cellular mechanical sensing for microgrooved surfaces has not been clarified yet. Here we investigated the migration responses of cells on the microgrooved substrate in consideration of the effects of cell type differences. We cultured vascular smooth muscle cells (VSMCs) obtained from different animal species (porcine aortic smooth muscle (PASM) cells and rat aortic smooth muscle (RASM) cells) and cervical cancer cells (HeLa) on the microgrooved substrate with 2-μm groove width and approximately 200-nm groove depth, and assessed the shape changes and migration behavior of the cells. Both types of VSMCs migrated directionally on the microgrooved substrate, but their detailed responses were quite different: PASM cells became more elongated shape on the microgrooves while maintaining their adhesion area and exhibited marked directional migration on the grooves. In contrast, RASM cells showed a significant reduction of adhesion area on the microgrooved substrate and they occasionally locomoted obliquely on the grooves. Interestingly, HeLa cells did not elongate in their shape on the microgrooved substrate with random migration direction, indicating that HeLa cells could not sense the microgrooved surfaces. These results indicate that the changes in cell shape and migration behavior might be dependent on the difference in intracellular structure due to the cell type differences, and these differences can be emphasized by the culture on the microgrooved surfaces.

Analysis of cell migration on the micro-grooved substrate for application of cell sorting ～Cell type-differences of the mechanical sensing for microgroove surfaces～

Analysis of cell migration on the micro-grooved substrate for application of cell sorting ～Cell type-differences of the mechanical sensing for microgroove surfaces～

Stable Omniphobic Anisotropic Covalently Grafted Slippery Surfaces for Directional Transportation of Drops and Bubbles

AbstractDirectional transportation and collection of liquids and bubbles are highly desirable in human life and industrial production. As one of the most promising types of functional surfaces, the reported anisotropic slippery liquid‐infused porous surfaces (SLIPSs) demonstrate unique advantages in liquid directional transportation. However, anisotropic SLIPSs readily suffer from the depletion of lubricant when used to manipulate droplets and bubbles, which leads to unstable surface properties. Therefore, fabricating stable anisotropic slippery surfaces for the directional transportation of drops and bubbles remains a challenge. Here, stable anisotropic covalently grafted slippery surfaces are fabricated by grafting polydimethylsiloxane molecular brushes onto directional microgrooved surfaces. The fabricated surfaces show remarkable anisotropic omniphobic sliding behaviors towards droplets with different surface tensions ranging from 72.8 to 37.7 mN m−1 in air and towards bubbles underwater. Impressively, the surface maintains outstanding stability for the transportation of droplets (in air) and air bubbles (underwater) even after 240 d. Furthermore, anisotropic self‐cleaning towards various dust particles in air and directional bubble collection underwater are achieved on this surface. This stable anisotropic slippery surface has great potential for applications in the directional transportation of liquids and bubbles, microfluidic devices, directional drag reduction, directional antifouling, and beyond.

Influence of micro-groove attributes on frictional power loss and load-carrying capacity of hybrid thrust bearing

PurposeMicro-surface texturing is emerging as a possible way to enhance the tribological performance of hydrodynamic fluid film bearings. In view of this, numerical simulations are carried out to examine the influence of surface texture on performance of hybrid thrust bearing system. This paper aims to determine optimum attributes of micro-grooves for thrust bearing operating in hybrid mode.Design/methodology/approachAn iterative source code based on finite element formulation of Reynolds equation has been developed to numerically simulate flow of lubricant through the bearing. Mass-conserving algorithm based on Jakobsson–Floberg–Olsson (JFO) condition has been used to numerically capture cavitation phenomenon in the bearing. Gauss Siedel method has been used to obtain steady state performance parameters of the bearings.FindingsA parametric study has been performed to improve the load supporting capacity of the bearing by optimizing micro-groove attributes and configuration. It is noticed that use of full-section micro-groove is beneficial in improving the efficiency of bearing by enhancing the fluid film reaction and reducing the film frictional power losses.Originality/valueThis study is helpful in examining the usefulness of micro-groove textured surfaces in hybrid thrust bearing applications.

Effects of different implant materials and surface microgrooves on the biological behavior of gingival fibroblasts

Objective: To study the effect of microgroove surface modification of titanium and zirconia on the biological behavior of gingival fibroblasts in order to find suitable surface materials for the transmucosal part of the dental implant. Methods: Twenty specimens were divided into four groups: smooth titanium (Ti-S), smooth zirconia (ZC-S), microgroove titanium (Ti-MG) and microgroove zirconia (ZC-MG) (five specimens in each group). Microgroove modification of titanium and zirconia surfaces was carried out by using fine machining chip system in the last two groups. The width of groove ridge was 60 μm, the width of groove was 60 μm, the depth of groove was 10 μm. The surface morphologies (the groove width and depth) were observed by scanning electron microscope (SEM), the surface roughness, static contact angle and elemental of specimens in each group were detected by SEM, atomic force microscope (AFM), optical contact angle measuring device and energy-dispersion X-ray analysis (EDX). Morphology of human gingival fibroblast (HGF) that arranged along the groove was analyzed using laser scanning confocal microscope by immunofluorescence staining. Differences in cell proliferation were analyzed and compared using cell counting kit. Expression level of intergrin α(5), β(1) and collagen Ⅰ mRNA were compared among different groups by quantitative real-time PCR for 6 h and 3 d. Results: The surface roughness of smooth titanium group and smooth zirconia group was (63.23± 2.55) and (26.78±3.11) nm, respectively. Microgroove zirconia group showed the best hydrophilicity: the static contact angle was 51.2°±2.0°. HGF was arranged along the groove surface, and cell proliferation results showed that proliferation on microgroove zirconia was more significant than that on other groups from 6 h to 7 d (P<0.05). Intergrin α(5) mRNA has the highest expression in microgroove zirconia (P<0.05) in the early adhesion (6 h), and there was no significant difference in the surface expression of intergrin β(1) and collagen Ⅰ mRNA in the early adhesion (6 h) of each group. However, in the late adhesion (3 d), intergrin α(5), β(1) and collagenⅠ mRNA expression in microgroove surface groups were higher than those of the smooth groups (P<0.05). Conclusions: Microgroove zirconia surface has small roughness and good hydrophilicity, which can guide HGF to line up in the groove, and this is beneficial to the HGF proliferation and the expression of structural proteins and functional proteins.

Enhanced Osseointegration of Titanium Alloy Implants with Laser Microgrooved Surfaces and Graphene Oxide Coating.

Rapid and effective osseointegration, as a critical factor in affecting the success rate of titanium (Ti) implants in orthopedic applications, is significantly affected by their surface microstructure and chemical composition. In this work, surface microgrooved Ti-6Al-4V alloys with graphene oxide coating (Ti-G-GO) were fabricated by a combination of laser processing and chemical assembly techniques. The osteogenic capability in vitro and new bone formation in vivo of the implants were systematically investigated, and biomechanical pull-out tests of the screws were also performed. First, in vitro studies indicated that the optimal microgroove width of the titanium alloy surface was 45 μm (Ti-G), and the optimum GO concentration was 1 mg/mL. Furthermore, the effects of the surface microstructure and GO coating on the in vitro bioactivity were investigated through culturing bone marrow mesenchymal stem cells (BMSCs) on the surface of titanium alloy plates. The results showed that the BMSCs cultured on the Ti-G-GO group exhibited the best adhesion, proliferation, and differentiation, compared with that on the Ti-G and Ti groups. Micro-computed tomography evaluation, histological analysis, and pull-out testing demonstrated that both Ti-G and Ti-G-GO implants had the higher osseointegration than the untreated Ti implant. Moreover, the osteogenic capability of the Ti-G-GO group appeared to be superior to that of the Ti-G group, which could be attributed to the improvement of surface wettability and apatite formation by the GO coatings. These results suggest that the combination of the microgroove structure and GO coatings exhibits considerable potential for enhancing the surface bioactivation of materials, and the combination modification is expected to be used on engineered titanium alloy surfaces to enhance osseointegration for orthopedic applications.

Modeling and Measurement on the Sliding Behavior of Microgrooved Surfaces.

The sliding behavior of anisotropic surfaces is a crucial property to their applications from fundamental research to practical fields. Herein, we propose a theoretical model for analyzing the sliding behavior based on the concept of adhesion energy. Surface Evolver simulation is conducted to determine the adhesion energy per unit area. The microgrooved surfaces are fabricated and characterized to validate the proposed theory. It is found that the apparent contact angle measured along the direction parallel to the strips increases with the increase of microgroove width, while the corresponding sliding angles exhibit an opposite trend. The adhesion energy per unit area has a constant value regardless of the droplet volume. The different sliding behaviors of anisotropic surfaces along the perpendicular and parallel directions are attributed to the difference in the corresponding adhesion energies per unit area. The proposed model is expected to be used for predicting the sliding behavior of anisotropic surfaces.

Focal adhesion clustering drives endothelial cell morphology on patterned surfaces.

In many cell types, shape and function are intertwined. In vivo, vascular endothelial cells (ECs) are typically elongated and aligned in the direction of blood flow; however, near branches and bifurcations where atherosclerosis develops, ECs are often cuboidal and have no preferred orientation. Thus, understanding the factors that regulate EC shape and alignment is important. In vitro, EC morphology and orientation are exquisitely sensitive to the composition and topography of the substrate on which the cells are cultured; however, the underlying mechanisms remain poorly understood. Different strategies of substrate patterning for regulating EC shape and orientation have been reported including adhesive motifs on planar surfaces and micro- or nano-scale gratings that provide substrate topography. Here, we explore how ECs perceive planar bio-adhesive versus microgrooved topographic surfaces having identical feature dimensions. We show that while the two types of patterned surfaces are equally effective in guiding and directing EC orientation, the cells are considerably more elongated on the planar patterned surfaces than on the microgrooved surfaces. We also demonstrate that the key factor that regulates cellular morphology is focal adhesion clustering which subsequently drives cytoskeletal organization. The present results promise to inform design strategies of novel surfaces for the improved performance of implantable cardiovascular devices.

Nano controlled dual release of bone morphogenic protein‐2 and insulin‐like growth factor‐1 and titanium surface microgrooves enhance osteoblastic differentiation of human mesenchymal stem cells

Nano controlled dual release of bone morphogenic protein‐2 and insulin‐like growth factor‐1 and titanium surface microgrooves enhance osteoblastic differentiation of human mesenchymal stem cells

An experimental investigation of the melting process of an ice bead on the smooth and micro-grooved surfaces under a hot shear flow

In the present study, we experimentally investigated the melting process of an ice bead on the smooth and micro-grooved surfaces under a hot shear flow. One smooth silicon surface and three micro-grooved silicon surfaces were fabricated and tested. A parameter study of the substrate surface temperature and the air flow speed was conducted. During the experiment, an ice bead was first formed from a freezing water droplet on a cold substrate surface. Then, the ice bead was exposed to a hot shear flow and its melting process was recorded by a CCD camera and an infrared camera simultaneously. As for the micro-grooved surfaces, the direction of the hot shear flow was parallel to the micro-grooves. The results showed that the melting process of the ice bead on the smooth and micro-grooved surfaces under a hot shear flow could be divided into three categories. The air flow speed, the surface temperature, and the type of the surface had a significant influence on which category the melting process of the ice bead belonged to. Besides, the presence of the micro-grooves was found to apparently affect the wetting length, the removable time, and the temperature along the centerline of the ice bead. In general, the micro-grooved surfaces were found to be more favorable for the ice bead melting process than the smooth surface.

Investigation of tribological performance of micro-groove textured cemented carbide surfaces

ABSTRACT Three kinds of grooved textures with different geometric patterns were prepared on cemented carbide tool surfaces. Finite element software FLUENT was used to simulate and analyse the fluid pressure of lubricants on the different micro-groove textured surfaces. Friction and wear experiments of titanium alloy balls and cemented carbides were carried out to investigate the tribological properties. The results show that the friction coefficient of the line groove textured surface is the smallest under dry friction conditions. Moreover, the friction coefficient of the sinusoidal groove textured surface is the smallest under fluid lubricated conditions. Experimental results show that lubrication of the grooved textured surfaces is consistent with the numerical simulation results. The main friction reduction mechanism of textures involves reducing the contact area of friction pairs and capturing debris under unlubricated conditions and supplying lubrication to form a continuous lubrication film and producing a dynamic pressure effect under fluid lubricated conditions.

Predictions of the effective slip length and drag reduction with a lubricated micro-groove surface in a turbulent channel flow

We perform direct numerical simulations of a turbulent channel flow with a lubricated micro-grooved surface to investigate the effects of this surface on the slip characteristics at the interface and the friction drag. The interface between water and lubricant is assumed to be flat, i.e. the surface-tension effect is neglected. The solid substrate, where a lubricant is infused, is composed of straight longitudinal grooves. The flow rate of water inside the channel is maintained constant, and a lubricant layer under the interface is shear driven by the turbulent water flow above. A turbulent channel flow with a superhydrophobic (i.e. air-lubricated) surface having the same solid substrate configuration is also simulated for comparison. The results show that the drag reduction with the liquid-infused surface highly depends on the lubricant viscosity as well as the groove width and aspect ratio. The amounts of drag reduction with the liquid-infused surfaces are not as good as those with superhydrophobic surfaces, but are still meaningfully large. For instance, the maximum drag reduction by the heptane-infused surface is approximately 13 % for a rectangular groove whose spanwise width and depth in wall units are 12 and 14.4, respectively, whereas a superhydrophobic surface with the same geometry results in a drag reduction of 21 %. The mean slip length normalized by the viscosity ratio and groove depth depends on the groove aspect ratio. The ratio of fluctuating spanwise slip length to the streamwise one is between 0.25 (ideal surface without groove structures) and 1 (i.e. isotropic slip), indicating that the slip is anisotropic. Using the Stokes flow assumption, the effective streamwise and spanwise slip lengths are expressed as a function of groove geometric parameters and lubricant viscosity. We also suggest a predictive model for drag reduction with the heptane-lubricated surface by combining the predicted effective slip lengths with the drag reduction formula used for riblets (Luchini et al., J. Fluid Mech., vol. 228, 1991, pp. 87–109). The predicted drag reductions are in good agreements with those from the present and previous direct numerical simulations.

Vibration assisted high-speed wire electric discharge machining for machining surface microgrooves

A microgrooved surface structure has broad application prospects in areas such as surface hydrophobic drag reduction, catalyst loading, and heat dissipation. In this study, a low-frequency vibration-assisted technique with the advantages of high efficiency, low cost, and wide material adaptability was proposed for high-speed wire electric discharge machining (WEDM-HS) to fabricate microgroove surface structures on metal plates. First, a linear motor was utilized as the driving source to load low-frequency vibrations (less than 10 Hz) onto the wire to machine microgrooves. Then, the forming mechanism of the microgroove structure was established. Next, the effect of each of the main processing parameters, including the pulse-on time, pulse-off time and feed rate, on the groove depth, groove width and ridge width of the microgroove, was investigated. Experimental results revealed that the established model is approximately consistent with the experimental data. Furthermore, a microgroove surface hydrophobic structure was successfully fabricated using this method, and the test results indicated that this structure can significantly improve the hydrophobic properties of the metal surface. Thus, the use of this vibration device enables conventional wire-cutting machine tools to manufacture microgroove surface functional structures efficiently and inexpensively, while also facilitating the expansion of the processing range of the microgroove size.

Self-Sustained Cascading Coalescence in Surface Condensation.

Sustained dropwise condensation of water requires rapid shedding of condensed droplets from the surface. Here, we elucidate a microfluidic mechanism that spontaneously sweeps condensed microscale droplets without the need for the traditional droplet removal pathways such as use of superhydrophobicity for droplet rolling and jumping and utilization of wettability gradients for directional droplet transport among others. The mechanism involves self-generated, directional, cascading coalescence sequences of condensed microscale droplets along standard hydrophobic microgrooves. Each sequence appears like a spontaneous zipping process, can sweep droplets along the microgroove at speeds of up to ∼1 m/s, and can extend for lengths more than 100 times the microgroove width. We investigate this phenomenon through high-speed in situ microscale condensation observations and demonstrate that it is enabled by rapid oscillations of a condensate meniscus formed locally in a filled microgroove and pinned on its edges. Such oscillations are in turn spontaneously initiated by coalescence of an individual droplet growing on the ridge with the microgroove meniscus. We quantify the coalescence cascades by characterizing the size distribution of the swept droplets and propose a simple analytical model to explain the results. We also demonstrate that, as condensation proceeds on the hydrophobic microgrooved surface, the coalescence cascades recur spontaneously through repetitive dewetting of the microgrooves. Lastly, we identify surface design rules for consistent realization of the cascades. The hydrophobic microgrooved textures required for the activation of this mechanism can be realized through conventional, scalable surface fabrication methods on a broad range of materials (we demonstrate with aluminum and silicon), thus promising direct application in a host of phase-change processes.