Triboelectric‘electrostatic tweezers'for manipulating droplets on lubricated slippery surfaces prepared by femtosecond laser processing

The use of‘Electrostatic tweezers'is a promising tool for droplet manipulation,but it faces many limitations in manipulating droplets on superhydrophobic surfaces.Here,we achieve noncontact and multifunctional droplet manipulation on Nepenthes-inspired lubricated slippery surfaces via triboelectric electrostatic tweezers(TETs).The TET manipulation of droplets on a slippery surface has many advantages over electrostatic droplet manipulation on a superhydrophobic surface.The electrostatic field induces the redistribution of the charges inside the neutral droplet,which causes the triboelectric charged rod to drive the droplet to move forward under the electrostatic force.Positively or negatively charged droplets can also be driven by TET based on electrostatic attraction and repulsion.TET enables us to manipulate droplets under diverse conditions,including anti-gravity climb,suspended droplets,corrosive liquids,low-surface-tension liquids(e.g.ethanol with a surface tension of 22.3 mN·m^(-1)),different droplet volumes(from 100 nl to 0.5 ml),passing through narrow slits,sliding over damaged areas,on various solid substrates,and even droplets in an enclosed system.Various droplet-related applications,such as motion guidance,motion switching,droplet-based microreactions,surface cleaning,surface defogging,liquid sorting,and cell labeling,can be easily achieved with TETs.

Carnivorous plants inspired shape-morphing slippery surfaces

Carnivorous plants,for instance,Dionaea muscipula and Nepenthes pitcher plant,inspired the innovation of advanced stimuli-responsive actuators and lubricant-infused slippery surfaces,respectively.However,hybrid bionic devices that combine the active and passive prey trapping capabilities of the two kinds of carnivorous plants remain a challenge.Herein,we report a moisture responsive shape-morphing slippery surface that enables both moisture responsive shapemorphing and oil-lubricated water repellency for simultaneous active-and passive-droplet manipulation.The moisture deformable slippery surface is prepared by creating biomimetic microstructures on graphene oxide(GO)membrane via femtosecond laser direct writing and subsequent lubricating with a thin layer of oil on the laser structured reduced GO(LRGO)surface.The integration of a lubricant-infused slippery surface with an LRGO/GO bilayer actuator endows the actuator with droplet sliding ability and promotes the moisture deformation performance due to oil-enhanced water repellency of the inert layer(LRGO).Based on the shape-morphing slippery surface,we prepared a series of proof-of-concept actuators,including a moisture-response Dionaea muscipula actuator,a smart frog tongue,and a smart flower,demonstrating their versatility for active/passive trapping,droplet manipulation,and sensing.

Photo-responsive droplet manipulation slippery lubricant-infused porous surface with ultra-high durability

Photo-responsive slippery lubricant-infused porous surface(SLIPS) for droplet manipulation is flexible, noncontact and non-destructive in droplet manipulation, which has promising applications in flexible robotics, microfluidics,biomedicine, and chemical analysis. However, the repeated manipulations for droplets of SLIPSs are quite limited in the works reported so far, the poor durability of droplet manipulation severely limits the practical application of the surfaces. In this paper, an Fe3O4-doped polydimethylsiloxane(PDMS)-based SLIPS is proposed and implemented to achieve ultra-high repeated droplet manipulation numbers under near-infrared ray(NIR) laser irradiation. Firstly, a micron columnar array structure with micro-pits on the top side, as well as, a wall structure out of the array is designed on SLIPS to reserve the lubricant. Secondly, the prototype of the SLIPS is fabricated by a 3-step ultraviolet(UV) lithography, and subsequently immersed in silicone oil for more than 96 h to obtain the ultra-high durability slippery lubricant-infused porous surface(UD-SLIPS). With a power of 25 m W–85 m W NIR laser, the repeated manipulation of microdroplets(≤ 5 μL) in the scale of 1 cm can exceed more than 3000 times which is far beyond that in previous reports. Finally, the droplet manipulation performance of this photo-responsive UD-SLIPS and the influence of infusion time on durability are investigated. The mechanism of the PDMS swelling effect is found to be the key factor in improving the droplet manipulation durability of SLIPS. The findings of this work would be of great significance for the development of highly durable photo-responsive functional surfaces for droplet manipulation.

Recent advances in slippery liquid-infused surfaces with unique properties inspired by nature

The slippery liquid-infused porous surface(s)(SLIPS)that imitates the Nepenthes pitcher plant has proven to be highly versatile and can be combined with various surface characteristics such as dynamic response,antifouling,selective adhesion,and optical/mechanical tunability.In addition,the introduction of a lubricating fluid layer also gives it extremely low contact angle hysteresis and self-repairing properties,which further expands its application range.Currently,SLIPS has been proven to be suitable for many frontier fields such as aerospace,communications,biomedicine,and microfluidic manipulation.In this review,we explain the theoretical background of SLIPS and the preparation methods currently available,including the choice of substrate materials and lubricants,and we discuss the design parameters of the liquid injection surface and how to deal with the consumption of lubricants in practical applications.In addition,the paper focuses on current and potential applications,such as preventing pathogen contamination of and blood adhesion of medical equipment,manipulation of tiny droplets,and directional transportation of liquids.Finally,some weaknesses that appear when SLIPS is used in these applications are pointed out,which provides a new perspective for the development of SLIPS in the future.

Smart Manipulation of Gas Bubbles in Harsh Environments Via a Fluorinert-Infused Shape-Gradient Slippery Surface

Fundamental research and practical applications have examined the manipulation of gas bubbles on open surfaces in lowsurface-tension,high-pressure,and high-acidity,-alkalinity,or-salinity environments.However,to the best of our knowledge,effi cient and general approaches to achieve the smart manipulation of gas bubbles in these harsh environments are limited.Herein,a Fluorinert-infused shape-gradient slippery surface(FSSS)that could eff ectively regulate the behavior of gas bubbles in harsh environments was successfully fabricated.The unique capability of FSSS was mainly attributed to the properties of Fluorinert,which include chemical inertness and incompressibility.The shape-gradient morphology of FSSS could induce asymmetric driving forces to move gas bubbles directionally on open surfaces.Factors infl uencing gas bubble transport on FSSS,such as the apex angle of the slippery surface and the surface tension of the aqueous environment,were carefully investigated,and large apex angles were found to result in large initial transport velocities and short transport distances.Lowering the surface tension of the aqueous environment is unfavorable to bubble transport.Nevertheless,FSSS could transport gas bubbles in aqueous environments with surface tensions as low as 28.5±0.1 mN/m,which is lower than that of many organic solvents(e.g.,formamide,ethylene glycol,and dimethylformamide).In addition,FSSS could also realize the facile manipulation of gas bubbles in various aqueous environments,e.g.,high pressure(~6.8 atm),high acidity(1 mol/L H 2 SO 4),high alkalinity(1 mol/L NaOH),and high salinity(1 mol/L NaCl).The current fi ndings provide a source of knowledge and inspiration for studies on bubble-related interfacial phenomena and contribute to scientifi c and technological developments for controllable bubble manipulation in harsh environments.

受猪笼草启发的仿生超滑表面研究进展

自然界中猪笼草的袋状叶片内壁呈多孔结构,能锁住其分泌的蜡状物质,受此启发,向粗糙基底灌注低表面能液体以形成稳定的润滑油层,进而制备出注液超滑表面,其比超疏水表面具有更耐久的疏液、自清洁、防附着等性能,成为当前研究的热点。基于此,该文介绍了仿生超滑表面的润湿理论及作用机制,综述了超滑表面构建技术策略,包括粗糙基底成形-润滑油灌注与粗糙基底成形-基底化学修饰-润滑油灌注2种典型的路径;全面总结了粗糙基底的制备方法,包括刻蚀法、溶胶-凝胶法、呼吸图法、水热法,并介绍了仿生超滑表面在油水分离、水雾收集、防腐蚀、液滴操控、防覆冰领域的应用进展;最后,对仿生超滑表面的发展前景进行了展望。

公路岩质边坡工程的开挖稳定性分析

针对闽清县X127线省璜镇省璜至谷洋段公路改建工程某处边坡,对其进行开挖的稳定性分析。通过FLAC3D软件,进行“层-面-层”模型的构建并对其进行分析,同时设定3个监测桩对特征点的位移以及水平应力进行分析,以得到滑面,进行开挖稳定性的模拟。依据推力以及稳定参数,进行相应的锚固设计,同时经过验证,方案实际可行,能够保证开挖边坡坡体稳定。

形状记忆磁性润滑表面的制备及对超顺磁液滴的滑动操控

将磁性粒子与形状记忆聚合物复合,通过设计渐变式构型构筑了梯度形状磁性材料,并与润滑涂层相结合,制备了一种磁性润滑表面.在磁性梯度的作用下,超顺磁液滴在表面上能够自发定向运动.借助于材料形状记忆效应对表面区域形态进行可逆调控,进一步展示了超顺磁液滴自发定向运动过程中的启停开关式控制,实现了将液滴定向自发运输与启停控制相结合.考察了磁性粒子含量对材料形状记忆性能的影响,以及区域形态调控尺寸与液滴滑动性能间的相互关系.机理分析进一步阐明磁场梯度提供的定向驱动力促使液滴定向自发输运,表面区域形态控制的可逆调控则可以在液滴运动过程中增加/消除黏滞阻力,基于两种因素的协同作用,可以实现对超顺磁液滴运动的智能操控.

电解液pH值对镁合金表面灌注液体型光滑多孔表面耐腐蚀性能的影响

在AZ31镁合金表面制备灌注液体型光滑多孔表面(SLIPS),从而为镁合金提供腐蚀防护。将粗糙多孔的层状双金属氢氧化物(LDH)作为纳米容器,用以盛放液体润滑液。通过调节电解液的pH值,获得用于构筑SLIPS的最佳LDH膜层。研究不同pH值对SLIPS表面形貌、表面润湿性和电化学行为的影响规律。结果表明,当pH值为10.5时,所制备的MgAl-LDH膜层厚度最大,为3.51μm,其可盛放最多的硅油,质量高达0.22mg/mm^(2),使得该MgAl-LDH膜层所构筑的SLIPS可为镁合金提供最优的腐蚀防护性能,腐蚀电流密度最低,为3.72×10^(-9)A/cm^(2)。另一方面,与超疏水表面相比,无论在电化学测试还是在长期浸泡试验中,SLIPS均可为AZ31镁合金基体提供更好的腐蚀防护。镁合金耐腐蚀性能的提高将进一步促进其在实践中的广泛应用。

MWCNTs光热相变超滑表面的制备及防/除冰性能研究

目的制备光热相变超滑表面,并研究不同含量的多壁碳纳米管(MWCNTs)和固体石蜡对防冰/除冰性能的影响。方法首先在纯Al表面刻蚀出微米结构,然后将MWCNTs、固体石蜡以及环氧树脂均匀混合后刮涂在处理后的Al基材表面,制备光热相变超滑表面,并对其润湿性、结冰/除冰性、机械稳定性以及自修复性进行表征。结果通过扫描电镜对涂层截面表征发现MWCNTs已经完全均匀分布在涂层内部。当用波长为808 nm、功率密度为0.5 W/cm2的近红外光(NIR)照射涂层,表层的固体石蜡融化成液体后水滴滑动角可由40°下降到5°,表现出极佳的滑动性能。在–20℃时,与纯Al基底相比,相变超滑表面可将水滴的结冰时长从27s延长至239s,其冰黏附强度降也只有34.9k Pa。得益于MWCNTs优异的光热性能,在NIR照射下,表面温度迅速升高,可在92s内实现快速除冰。此外,涂层在100次的循环摩擦后依然保持极低的冰黏附强度,并在NIR照射下可实现快速自修复。结论光热相变超滑表面相比于纯Al表面具有更加优异的防冰性,MWCNTs的加入,使表面具有快速除冰性。环氧树脂和固体石蜡则极大地提高了表面耐磨性以及自修复性,为长久的防冰/除冰提供了保障。

含硅氧烷超滑表面的制备及其性能

文中利用端氨基聚硅氧烷(APT-PDMS)和顺丁烯二酸酐酯化β-环糊精(β-CD-MAH)进行反应,再通过金属配位反应引入铁离子,制备了聚硅氧烷-顺丁烯二酸酐酯化β-环糊精(APT-PDMS-co-β-CD-MAH)。分别通过红外光谱、核磁共振、紫外分光光度计检验了聚合物的组成与结构。采用操作简单、低成本的呼吸图法创新性地制备了特殊多层次孔结构膜,通过静态接触角测试仪测试了多孔结构膜的疏水性能,通过场发射扫描电子显微镜观察了多孔结构膜的表面形貌。结果表明,当APT-PDMS相对分子质量为3504、APT-PDMS与β-CDMAH的摩尔比为3∶1、聚合物浓度为25 mg/mL时制备的多孔基底及SLIPS性能最佳,该多孔基材结构中的大孔包含2~3个小孔,且小孔内还包含多个纳米级孔洞,静态接触角大于150°。灌入硅油后,滑动角小于10°,且该超滑表面(SLIPS)具有良好的稳定性、自清洁性、防冰抗冻及抗细菌黏附性。

316L不锈钢超滑表面的制备及抗生物粘附性能研究

采用两步阳极氧化法在316L不锈钢表面制备了双层纳米多孔结构,然后采用十三氟辛基硅烷/乙醇溶液对其进行改性。最后将4种不同黏度的全氟聚醚注入改性后的双层纳米多孔结构中,形成4种不同黏度的超滑表面。对比研究了全氟聚醚的黏度对超滑表面润湿性、微观形貌和防污性能的影响。结果表明,相比于低黏度超滑表面和高黏度超滑表面,中黏度超滑表面同时具有稳定的润滑油层和低的水滑动角。与灌注全氟聚醚前的316L不锈钢表面相比,超滑表面的抗小球藻粘附性能大幅提高。在静态培养条件下,除了灌注高黏度全氟聚醚的超滑表面因润滑油层流动性差而导致抗小球藻粘附性较差之外,其他黏度的超滑表面的抗小球藻附着性能都良好。在动态培养条件下,由于水流的剪切作用,高黏度超滑表面的抗小球藻粘附性能明显提高,但较低黏度超滑表面的抗小球藻粘附性能有所下降。

Development of Slippery Liquid-Infused Porous Surface on AZ31 Mg Alloys for Corrosion Protection

The relatively poor corrosion resistance remarkably limits the wide applications of Mg alloys in practice,although they possess many attractive properties,like low density,high specific strength,and good biocompatibility.The formation of a protective coating can effectively suppress the corrosion.In this work,a slippery liquid-infused porous surface(SLIPS),with good surface hydrophobicity,stability,and self-healing property,was formed on AZ31 Mg alloys.The development of SLIPS requires suitable porous micro/nanostructures.Layered double hydroxide(LDH),with effective corrosion resistance for Mg alloys,was a good candidate to accommodate the liquid lubricant.Especially,different temperatures were applied to in situ form MgAl-LDH on AZ31 Mg alloys.The results showed that the temperature of 120℃was the best condition for the SLIPS to provide good corrosion protection for Mg alloys,with the lowest corrosion current density of 3.19×10^(-9)A cm^(−2).In addition,the SLIPS performed well in the long-term immersion test and abrasion test.The AZ31 Mg alloys with superior corrosion resistance and good mechanical and chemical stability can be extensively applied in areas of automotive,electronics,and aerospace.

Molecular Dynamics Simulations of the Effects of Surface Sinusoidal Nanostructures on Nanoscale Liquid Film Phase-Change

Nanostructures on heat transfer surfaces can enhance micro/nanoscale phase-change heat transfer processes. To understand the enhancement mechanisms provided by nanostructures, evaporation processes of nanoscale liquid films on periodic sinusoidal-shaped surfaces were investigated via molecular dynamics simulations. By changing the amplitudes(A) and periods(T) of the curves describing the sinusoidal shapes, which possess shapes similar to f(x)=h0+Asin(2πx/T), sinusoidal surfaces of different sizes were constructed. An unevaporated region always existed on the copper plate for all surfaces during phase-change processes. Moreover, we calculated the interfacial thermal resistances and the mismatches between the vibrational density of states of the solid and liquid for different surfaces. The results show that the argon temperature changes and evaporation rates during the phase-change process on sinusoidal surfaces are higher than those on flat surfaces, and these results increase with the increase in amplitudes and the decrease in periods within certain limits mainly because of the thermal resistance decrease at the solid-liquid interface. Furthermore, the corresponding mismatches between the vibrational density of states of the solid and liquid also decrease, which indicates that the existence of sinusoidal nanostructures enhances the heat transfer of the phase-change process.

Slippery Properties and the Robustness of Lubricant-impregnated Surfaces

Inspired by nepenthes pitcher plants,Lubricant-Impregnated Surfaces(LISs)are surfaces with lubricant infused in the textures which form slippery interfaces.In this paper,we investigated slippery properties and the robustness of LISs with different micro-texture topologies(i.e.,no textures,micro-pillar textures and micro hole textures),including original LISs and LISs rinsed by water.We measured the static contact angle,sliding angle and droplet motions on the LISs,using a contact angle instrument and a Particle Image Velocimetry(P1V)system.Similar contact angles and small sliding angles were observed on all original LISs,which indicated that an oil-layer existed on each LIS's interface.After rinsed by water,the sliding angle increased obviously and the slip velocity decreased,which meant that the LISs slippery properties deteriorated in different degrees.Among all the LISs in our experiments,LIS with micro pillar textures has the best slippery performance and robustness before and after rinsed.We found that the LISs'slippery properties were closely related to the states of the oil-layer on the interface,which were changed after rinsed.For the LIS with micro pillar textures,a thin layer of lubricant can sustain on the interface even after rinse,which made the droplet slide smoothly on the surface,with a lower sliding angle and a larger sliding velocity.This indicates that the proper micro-texture will enhance the slippery property and make it last longer.

Investigation of Anticorrosive Performance of Oil-infused Slippery and Superhydrophobic Brass Surfaces by Laser Texturing

Brass is widely used in machinery,electronic appliances and emerging industries.The corrosion resistance of laser-induced superhydrophobic surface of brass needs to be improved.In recent years,bionic surface with slippery coating has attracted much attention because of its excellent corrosion inhibition performance.Here,we first prepared the superhydrophobic surface of brass by nanosecond laser ablation combined with fluoroalkyl silane modification,and then injected silicone oil into the prepared superhydrophobic matrix to obtain a slippery coating surface.PDP and EIS tests in 3.5 wt.%NaCl solution showed that the corrosion resistance of the slippery surface was better than that of the superhydrophobic surface.This study can play a certain role in promoting the development of metal anticorrosive coating and is of great significance in the preparation of slippery surface by laser induction,and provides a convenient and eff ective means for metal anticorrosion in the industrial field.

纳秒激光诱导黄铜超疏水光滑涂层的抗盐腐蚀性能研究

黄铜是工业产品的重要基础性材料之一,其抗盐腐蚀性能的提升问题,近年来受到工业界和科研界的广泛关注。本文提出一种制备黄铜抗盐腐蚀涂层方法。首先,利用纳秒激光诱导出了具有微纳织构的黄铜超疏水表面,并用氟硅烷进行修饰增强其稳定性;然后在制备的超疏水性基体中注入硅油,获得超疏水光滑涂层表面;最后,浸入35wt%NaCl溶液中进行PDP和EIS测试,结果表明光滑表面的抗盐腐蚀性能优于普通超疏水表面,更优于原始黄铜表面。本研究可对金属防腐涂层发展起到一定的促进作用,对于激光诱导制备超疏水光滑表面具有重要意义,为工业领域的金属防腐蚀途径提供了方便和有效的手段。

浅析滑坡勘查过程中滑动面的确定方法

滑动面的确定不仅关系到治理方案的选择,同时关系到工程总体造价,直接决定滑坡治理的成败。仅靠单一钻探手段通常难以确定滑动面位置,需通过多种手段综合确定滑动面的空间位置。文中总结了国内现阶段常用的滑动面确定方法,并分析了各自的优缺点,得到各方法的适用范围,以期对工程实践提供一定指导。

龚滩新镇软弱易滑层稳定性的数值模拟分析

为了揭示龚滩新镇F-F′工程地质剖面AB段软弱易滑层的失稳机理,采用基于数值模拟的强度折减法对该段软弱易滑层的稳定性进行计算,并将计算结果与传统的传递系数法的计算结果进行比较。结果表明:AB段易滑层在工况Ⅲ下处于基本稳定状态,在工况Ⅳ下则处于欠稳定状态;M3层塑性区较贯通,且该塑性区前部向上反翘,产生次级剪出口,进入M2层,形成复合滑动面;当滑坡中存在多层软弱层且层间力学作用复杂时,传统的传递系数法假定的临界滑动面不太合理,会高估斜坡的稳定性,使稳定分析结果产生较大误差;基于数值模拟的强度折减法则能精准的找到更为合理的临界滑动面,因而比传统的极限平衡类分析法更合适用来计算稳定安全系数并揭示其失稳机理与破坏模式。