新型仿生微纳米界面微量流体输运调控材料

生物表面从微纳米层次上已提供给人类一种多级次梯度结构的协同效应机制,并展现出控制动态浸润性及液体传输的独特能力。基于这种机制,设计了各种仿生的结构,开发了制备仿生材料的新技术与方法。并将仿生理念引入到材料的制备中,通过利用常见的高分子材料、响应高分子材料、掺杂的有机物/无机物复合材料,可控制备了一系列新型一、二维度仿生微纳米界面材料。这些新型仿生微纳米界面材料从微、纳及宏观层次上体现了优越的浸润性调控功能,如液滴驱动、水收集、防覆冰等,其在微流控制、淡水采集、雾水工程、热量传递、浮尘过滤等领域有重要的应用前景。     

Hierarchical structures of anodised cold gas sprayed titanium coatings

Cold gas spray (CGS) titanium coatings have been produced to obtain porous and rough coatings with enhanced mechanical performance. The coatings from optimal spraying conditions reached tensile strength values up to 40?MPa, shear strength up to 39?MPa and a loss mass of 37?mg/100 cycles in abrasive testing, values in accordance with the ASTM standards to be applied for orthopaedic joint prostheses. An innovative hierarchical structure (micro-nano) consisted of a TiO₂ nanotubes top layer obtained by anodisation onto a CGS Ti coating. The present paper focuses on the characterisation of both surfaces, as-sprayed CGS Ti layer and double Ti-TiO₂ layer, in terms of mechanical properties, surface topography and wettability (contact angle). There were not significant changes in micro-roughness, Ra～40?µm and Ra～30?µm, but a significant decrease in contact angle, from ≈26° up to 0°, was observed between these two structures. This behaviour indicates that the combination of the CGS?+?anodising results in promising high roughness superhydrophilic surfaces, ideal for biomedical applications.     

超疏水表面微结构的设计及其注射成型

目的 从超疏水表面的功能设计出发,主动设计三种深宽比的微结构阵列并洞察其在不同润湿接触状态下的疏水性能。方法 首先,采用热力学分析方法,建立三种深宽比微结构的系统自由能与其接触角、结构几何参数之间的函数关系,探明自主设计微结构表面的润湿性能。继而,在热力学分析的基础上,采用紫外光刻、电铸和注射成型技术相结合的方法实现三种深宽比微结构聚丙烯（PP）超疏水表面的制备。最后,进一步测量与分析聚丙烯（PP）微结构表面的润湿性能。结果 三种深宽比微结构表面的静态接触角测量值均大于150?,滚动角分别为12?、14?和15?,基本达到设计目标;同时,微结构表面的表观接触角测量值与理论计算值基本符合。表面的接触角滞后分别为15?、21?、22?,且接触角滞后随着深宽比的增加而变大,使液滴在PP表面的流动性也变差。结论 在设计微结构超疏水表面的过程中,可以适当降低微结构的深宽比,以获取更好的超疏水特性。自主设计的微结构表面基本实现超疏水性,为高聚物超疏水表面的功能设计与高效制备提供了理论依据与技术支撑。     

纳秒激光加工微凹坑对YG3表面浸润性的影响

研究硬质合金刀具表面浸润性对提高刀具寿命和工件加工表面质量有重要的意义。采用波长1064 nm纳秒脉冲激光在硬质合金YG3表面加工微凹坑阵列,运用光学显微镜、光学轮廓仪和接触角测量仪分别测量微凹坑形貌和表面接触角,研究不同激光功率、扫描次数和微凹坑间距对表面形貌和接触角的影响规律。建立微凹坑几何形貌模型,基于Wenzel理论分析微凹坑形貌变化对表面接触角的影响机理。结果表明:随着平均功率和扫描次数的提高,微凹坑的直径和深度均增大;随着间距的减小,微凹坑分布密度增大。3种条件下表面粗糙度率均增大,表面接触角余弦值随粗糙度率的变化趋势基本一致且成正相关,所以接触角随粗糙度率增加而降低。通过实际接触角与推导接触角的曲线拟合得到了接触角方程。     

Tailoring cotton fabric with wettability gradient and anisotropic penetration of liquid by spray coating

Abstract

Comfort has been one of the most important features of clothing, particularly for sportswear, which requires an effective transport of heat and moisture from the inner to the outer side of clothing. We herein report the use of a simple technique of spray coating and commercially available water repellents for a one-sided hydrophobic and self-initiated one-way water transport cotton fabric. The highlight of this work is the simplicity of the process and choice of chemicals that can be adopted easily by any textile finishing industry. On this fabric, water was able to diffuse and penetrate the fabric structure in one direction from the hydrophobic to the hydrophilic side but was unable to go the opposite direction. The directional transport improved with smaller droplets and lower add-on achievable by higher air pressure and longer distance of spray coating. From moisture management tests, the best result was obtained with the spray coating of Phobol NB-NH at an air pressure of 3.0?kgf/cm² and a distance of 120?cm. Phobol NB-NH gave better result of transport and overall comfort properties than Phobotex RSY.     

Numerical investigation of water dynamics in a novel wettability gradient anode flow channel for proton exchange membrane fuel cells

The effective removal and transport of water in flow channels play an important role in the water management of proton exchange membrane fuel cells (PEMFCs). In this paper, a novel design of anode serpentine flow channel with the wettability gradient wall is discussed and numerically investigated by utilizing the volume-of-fluid (VOF) method. The effects of the contact angle and the wettability gradient of channel walls, as well as hydrogen flow velocity and water droplet size, on the droplet dynamic behavior are studied. The results indicate that compared with the conventional flow channel, the water droplet can be more effectively removed from the turning part in the wettability gradient flow channel. And the water removal ability in the turning part is improved with the increase of the wettability gradient. Moreover, the wettability gradient flow channel can also improve the water removal performance for the cases with different hydrogen flow velocities and water droplet sizes. This study provides ideas for guiding the design of flow channel to effectively enhance anode water management.     

Numerical simulation of liquid water emerging and transport in the flow channel of PEMFC using the volume of fluid method

Three-dimensional numerical simulation of liquid water emerging from the gas diffusion layer (GDL) surface to the gas flow channel in the proton exchange membrane (PEM) fuel cell (PEMFC) is carried out using the volume of fluid (VOF) method. The effects of the water velocity in the GDL hole, the airflow velocity and the wettability of the channel surfaces on the water emerging process and transport in the flow channel are investigated. It is found that at low water velocity, the water detaches from the water hole, forming discrete water droplets on the GDL surface, and is transported downstream on the GDL surface until removed from the GDL surface by the U-turn part of the flow channel; whereas at high water velocity, the continuous water column impinges the hydrophilic channel surface counter to the GDL surface, being directly removed from the GDL surface. The airflow velocity affects water detachment and impact process in the channel corner, and water droplet breakup is observed under high airflow velocity. The channel surface wettability influences water droplet shape and its transport in the channel. Rather than forming corner water films at the U-turn for hydrophilic channel surface, water maintains the droplet shape and smoothly passes through the U-turn for hydrophobic channel surface. The importance of the U-turn to the water removal is also discussed. The U-turn promotes water removal from the GDL surface at low water velocity and water breakup at high airflow velocity.     

Videokeratoscopic assessment of silicone hydrogel contact lens wettability using a new in-vitro method

PurposeThe aim of the study was to assess the surface wettability of new-generation silicone hydrogel (SiH) contact lenses (CLs) videokeratoscopically using a new in-vitro method under office conditions.MethodVideokeratoscopic methodology was used to compare time-dependent CL wettability on an in-vitro cornea model. The model cornea was a polished chrome surface coating a Teflon form. It was prepared with a base curve of 8.7 mm and a diameter of 15 mm. Laboratory temperature and humidity were controlled. Before and after placing CLs on the on the model cornea, Bausch + Lomb Biotrue® multi-purpose solution (MPS) was dropped to simulate the pre-lens and post-lens film layer. Fanfilcon A, Senofilcon A, Samfilcon A, and Lotrafilcon B CLs with -3.00D were used, and images were taken with the videokeratoscopic method for testing. In the control group, the same procedure was performed without placing CLs. The images of CLs at 0, 60, 90, 120, 150, and 180 s were taken. Distortions and gaps seen in rings were recorded. The areas in rings were calculated in pixels using İmageJ.ResultsWhen CLs were examined, statistical differences were found among average pixel values (p < 0,001). The average pixel value was 131877.4 in the Samfilcon group, 116125.5 in the Senofilcon group, 137893.2 in the Fanfilcon group, 125578.3 in the Lotrafilcon group, and 124984.6 in the control group. No difference was found between the average values of the Lotrafilcon group and the control group. Differences were found between the average values of all other groups.DiscussionThe results obtained showed that videokeratoscopy was an effective method for in-vitro testing of CL wettability. It was found that SiH lenses displayed different performance under office conditions depending on materials and technologies used for wetting the lens surface. It was shown that lens surface wettability could be measured with a repeatable and new method when the factors affecting surface wetness and image quality were ruled out.     

ZnO纳米结构晶体质量对其表面润湿性的影响

利用化学气相沉积法(CVD)在镀有Au(10nm)膜的石英衬底上通过控制O2流量制备不同形貌的纳米结构ZnO,通过X射线衍射(XRD)和变温光致发光谱研究晶体缺陷对ZnO表面润湿性能的影响。结果表明,除表面粗糙度之外,高密度的缺陷对样品表面润湿性能也有很重要的影响,尤其是氧空位缺陷对吸收羟基有利,能够降低ZnO表面自由能,提高其疏水性能。     

Effect of wall wettability condition on drift-flux parameters in lead–bismuth two-phase flow in circular and annular bubble columns

Lead–bismuth two-phase flow in a cylindrical vessel and annulus was experimentally investigated by varying the surface wettability of the vessel wall. The test section used in this study was a cylindrical stainless vessel with/without inner sleeve to change the hydraulic diameter. Volume-averaged void fraction was measured by varying the surface wettability of the test section, which was enhanced by using a soldering flux. Measured void fraction was compared with existing two-phase flow correlations and with one-dimensional theoretical simulations assuming one-dimensional drift-flux model. From experimental results, measured distribution parameters of the lead–bismuth two-phase flow are much larger than that of ordinary two-phase flow regardless of the surface wettability. In the present work, the one-dimensional analysis was carried out for the cylindrical vessel to reproduce the distribution parameter. From the simulation results, predicted value for the cylindrical vessel showed good agreement with experimental results. However, in annulus, the distribution parameters in annulus were underestimated by the present model. It was suggested that, in case of annulus, steeper void fraction profile might be formed near the inner surface for poor wettability condition.