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Switchable mechanically induced changes in the wetting behavior of surfaces are of para-mount importance for advanced microfluidic, self‐cleaning and biomedical applications. In this work we show that the well‐known polydimethylsiloxane (PDMS) elastomer develops self‐patterning when it is coated with nanostructured TiO2 films prepared by physical vapor deposition at glancing angles and subsequently subjected to a mechanical deformation. Thus, unlike the disordered wrinkled surfaces typically created by deformation of the bare elastomer, well‐ordered and aligned micro‐scaled grooves form on TiO2/PDMS after the first post‐deposition bending or stretching event. These regularly patterned surfaces can be reversibly modified by mechanical deformation, thereby inducing a switchable and reversible wetting petal effect and the sliding of liquid droplets. When performed in a dynamic way, this mechanical actuation produces a unique capacity of liquid droplets (water and diiodomethane) transport and tweezing, this latter through their selective capture and release depending on their volume and chemical characteristics. Scanning electron and atomic force microscopy studies of the strained samples showed that a dual‐scale rough-ness, a parallel alignment of patterned grooves and their reversible widening upon deformation, are critical factors controlling this singular sliding behavior and the possibility to tailor their response by the appropriate manufacturing of surface structures. European Union 899352 Ministerio de Ciencia e Innovación PID2019- 110430GB-C21, PID2019-109603RA-I0, MAT2013-40852-R, MAT2013- 42900-P Ministerio de Economía y Competitividad 201560E055 Junta de Andalucía AT17-6079, P18-RT-3480

In recent years, there has been an increasing interest in methods to fabricate hydrophobic surfaces. Hydrophobic surfaces have been used in multiple applications in microfluidic devices to control fluid flow, as self-cleaning surfaces and also in de-icing or for drag reduction. Conventionally, hydrophobic surfaces were created by laser processing, self-assembly and other chemical processing methods. However, in many of these methods, hydrophobicity of the surface cannot be maintained for an extended time or restricted to limited set of materials. In some applications, creation of anisotropy in the hydrophobic property and the ability to pattern it, is important. Here, a low-cost, high-throughput method to generate highly hydrophobic and anisotropic surface has been developed. This method uses Computer Numerical Control machining employing diamond tools whose tips have been micro-structured using Focused Ion Beam that enables parallelization and achieves at least four times higher machining speed compared with other methods. The versatility of this method has been demonstrated by machining both metal and polymeric materials. Significant anisotropic wetting has been observed on the machined surface with the anisotropy in directional contact angle of up to 71.6°. Highly-hydrophobic surfaces with contact angle of 163.1° on 6061 Aluminum Alloy and 155.7° on polymethyl methacrylate surface were created.

The directional light-induced mass migration phenomenon arising in the photoresponsive azobenzene-containing materials has become an increasingly used approach for the fabrication of controlled tridimensional superficial textures. In the present work we demonstrate the tailoring of the superficial wettability of an azopolymer by means of the light-driven reconfiguration of an array of imprinted micropillars. Few simple illumination parameters are controlled to induce nontrivial wetting effects. Wetting anisotropy with controlled directionality, unidirectional spreading, and even polarization-intensity driven two-dimensional paths for wetting anisotropy are obtained starting from a single pristine pillar geometry. The obtained results prove that the versatility of the light-reconfiguration process, together with the possibility of reversible reshaping at reduced costs, represents a valid approach for both applications and fundamental studies in the field of geometry-based wettability of solid surfaces.

This study investigated the wetting behavior of Ti6Al4V surfaces that were groove-structured by means of femtosecond laser irradiation. The material was treated under ambient air conditions by use of a laser wavelength of 1030 nm and a pulse duration of 300 fs. Highly accurate structures with a gap width of 20 &micro, m, a gap depth of 10 &micro, m, and varying strut widths (1&ndash, 300 &micro, m) were generated and the contact angles in parallel and perpendicular direction were determined using sessile drop method with ultrapure water 1, 8, and 15 days after irradiation. All deterministic surfaces exhibited a pronounced contact angle change over time. The structures showed a strong anisotropic wetting behavior with a maximum contact angle aspect ratio of 2.47 at a strut width of 40 &micro, m and a maximum difference between the parallel and perpendicular contact angle of 47.9&deg, after 1 day.

In recent years, there has been an increasing interest in the study of hydrophobic surfaces. Hydrophobic surfaces have been used in multiple applications in microfluidic devices due to their properties of self-cleaning, and also in deicing products. Conventionally, hydrophobic surfaces were created by laser cutting, self-assembly and other chemical processing methods. However, in most of these methods, hydrophobicity of the surface cannot be maintained for an extended time or restricted to limited set of materials. A low-cost, high-throughput method to generate highly hydrophobic anisotropic surface has been developed in this thesis which uses Computer Numerical Control (CNC) machining employing diamond tools whose tips have been micro-structured using Focused Ion Beam (FIB) built tips. The versatility of this method has been demonstrated by machining both metal and polymeric materials. Significant anisotropic wetting has been observed on the machined surface with the anisotropic contact angle can reach up to 71.6 degree and highly-hydrophobic property with contact angle of 163.1degree on 6061 Aluminum Alloy and 155.7 degree on PMMA surface. Thesis Master of Science in Mechanical Engineering (MSME)

Designing hydrophobic surfaces with controllable wettability has attracted much interest in the recent times. The present study seeks to simulate the static and dynamic wetting behavior of liquid droplets on horizontal flat and microgrooved surfaces and compare the findings with experimentally obtained data. Using an open-source software, a 3D drop-shape model is developed to numerically analyze the shape of liquid droplets and anisotropic wetting for a wide range of parametric space. The effects of droplet volume, variation in the microgroove geometry and wettability gradient along the parallel and perpendicular directions of the microgrooved surfaces etc . on the drop shape and apparent contact angle are examined. Simulation and analysis are extended to analyze the wetting behavior of V-grooved geometry and are compared with the findings on rectangular microgrooved surfaces. For creating wettability gradient along the parallel direction of the grooves, periodic PDMS (Polydimethylsiloxane) coating is considered and increased hydrophobicity of the surface is observed with significant increase in the parallel contact angle for this case. The simulated results manifest considerable differences in the wetting pattern of the microgrooved and flat surfaces and are found out to be in good agreement with the experimental findings.

Supplementary data associated with this article can be found, in the online version, at http://dx.doi.org/10.1016/j.eurpolymj. 2017.03.007, This manuscript describes the preparation of hierarchically, i.e. micro and nanometer scale ordered surfaces with variable functionality by simultaneously combining the microfabrication using Laser Interference Lithography (LIL) and the self-assembly of block copolymers occurring at the nanometer scale. The block copolymers employed in this study are a double hydrophobic poly(2,3,4,5,6-pentafuorostyrene)-block-polystyrene (P5FS-b-PS) and an amphiphilic polystyrene-block-poly(acrylic acid) (PS-b-PAA) diblock copolymer. The incorporation of these block copolymers in the photosensitive mixture resulted in surfaces with hierarchically micro and nanostructured interfaces with either hydrophobic or hydrophilic surface chemical composition. Moreover, in comparison with microstructured surfaces prepared using statistical copolymer with similar composition, the use of block copolymers enhanced both the surface wettability changes and the final anisotropic wetting. We evidenced herein that by preparing unidirectional micrometer size patterns with either P5FS-b-PS or PS-b-PAA the wetting anisotropy increases with the hydrophobicity or the hydrophilicity of the surface., The authors gratefully acknowledge support from the Consejo Superior de Investigaciones Científicas (CSIC). Equally, this work was financially supported by the Ministerio de Economía y Competitividad (MINECO) through MAT2013-47902-C2-1-R and MA T2016-78437-R (JRH). The authors thank for technical and human support provided by SGIker of UPV/EHU.

Mikroakışkanlar, çok küçük hacimlere sahip sıvıları, mikrometrelik kanallarda kontrol etme bilimidir. Mikroakışkanlar, kısa tepkime süresi ile çabuk analiz edilebilme ve taşınabilir özellikleriyle başlıca kimyasal ve biyolojik analizler olmak üzere daha birçok alanda teknolojik olarak uygulama bulmaktadır. Günümüzde mikroakiskan temelli cihazlar, litografi ve mikro-imalat gibi yöntemler ile cip üstü laboratuvar aygıtları olarak üretilmektedir. Ancak söz konusu üretim teknikleri, esneklik, biyolojik uyum, harici bileşenlerle bütünleşme ve üretim maliyetleri gibi yüksek önem arz eden konularda kısıtlamalara sahiptirler.Bu çalışmada, yüzeyi şekillendirilmiş polimer fiberler, ekonomik açıdan uygun mikroakışkan cihazların üretimi için yeni bir platform olarak sunulmuştur. Isıl fiber çekme metodu kullanılarak üretilen onlarca metre uzunluğundaki fiberler, yüzeylerinde 'V' şeklinde yivlerden oluşan yirmi kanal içermektedir. Fiber yüzeylerinin polidopamin (PDA) ve Ultraviyole/Ozon (UV/O) gibi işleme tekniklerle modifiye edilmesinden sonra fiberlerin üstündeki yivler boyunca kılcal hareketten kaynaklanan yayılma yönüne bağlı olarak sıvı akışkanlığı gözlemlenmiştir. Üç boyutlu esnek fiberlerden oluşan diziler üzerinde, herhangi bir harici pompa veya hareketlendirici mekanizma olmaksızın önceden belirlenmiş kanallarda kendiliğinden sıvı aktarımı sağlanabilmektedir. Ayrıca, yüzeyi organik olarak modifiye edilmiş nano parçacıklar V yapılı yivlerin üzerinde kullanılarak fiber yüzeylerin hidrofobikliği arttırılmıştır. Yüzeyleri şekillendirilmiş fiberlerin, esnek, sağlam, hafif ve ekonomik mikrodamlacık tabanlı aygıtların üretimi için oldukça uygun olduğuna ve mikroakışkan aygıtların kullanım alanlarını yeni ilaç keşifleri, tıbbi tanılama, yiyecek ve su kaynaklarının kalitesinin denetlenmesini de kapsayacak şekilde genişleteceğine inanılmaktadır. Microfluidics is the science of controlling low volumes of fluids in a microchannel. It is used in diverse area of applications such as chemical and biological analysis. Benefits of microfluidics are fast analysis, short reaction times, and portability of device. Current fabrication techniques of lab-on-a-chip microfluidic devices are soft lithography and micromachining. However, these methods suffer from design limitations such as flexibility of product, high cost, integration of external components, and biocompatibility.Surface textured polymer fibers are utilized as a novel platform for the fabrication of affordable microfluidic devices. Fibers are produced by thermal drawing technique tens of meters-long at a time and comprise twenty continuous and ordered V-grooves channels on their surfaces. Extreme anisotropic wetting behavior due to capillary action along the grooves of fibers is observed after surface modifications with polydopamine (PDA) coating and Ultraviolet/Ozone (UV/O) treatment. Three-dimensional arrays of flexible fibers spontaneously spread liquid on predefined paths without the need of external pumps or actuators. In addition, surface modification with organically modified silica nanoparticles was added on top of the V-grooves to enhance the hydrophobicity of the fiber surfaces. Surface textured fibers are well suited for the fabrication of flexible, robust, lightweight and affordable microfluidic devices which is believed to expand the role of microfluidics in a scope of fields including drug discovery, medical diagnostics and monitoring food and water quality. 116

An experimental study about the anisotropic wetting behavior of a surface patterned with parallel grooves is presented as an application example of a novel technique for investigation of complete and partial anisotropic wetting on structured surface by X-ray microtomography. Shape of glycerin droplets on such surface is investigated by X-ray micro computed tomography (microCT) acting as a non-intrusive, full volume 3D microscope with micrometric spatial resolution. The reconstructed drop volumes enable to estimate the exact volumes of the drops, their base contours, and 3D static contact angles, based on true cross-sections of the drop-surface couple. Droplet base contours are compared to approximate geometrical contour shapes proposed in the literature. Contact angles along slices parallel and perpendicular to the grooves direction are compared with each other. The effect of the sessile drop volume on the wetting behavior is discussed. The proposed technique, which is applicable for any structured surface, enables the direct measure of Wenzel ratio based on the microCT scan in the wetted region usually inapproachable by any others. Comparisons with simplified models are presented and congruence of results with respect to the minimum resolution needed is evaluated and commented.

The directional wetting characteristics of droplets on chemically defined stripe-patterned anisotropic substrates are briefly reviewed. The static droplet shape as well as the observed contact angles exhibit unique scaling behavior as a function of the macroscopic wettability, as arising from patterns consisting of alternating hy-drophilic and hydrophobic stripes. In addition, the motion of liquid from surface regions with low macroscopic wettability towards more wetting areas is described. Linear patterns are presented, which induce liquid movement along the chemically defined stripes giving rise to a macroscopic gradient in surface energy. Finally, we show that lattice Boltzmann modeling enables semrquantitatively accurate simulation of the experimental observations.

The directional wetting characteristics of droplets on chemically defined stripe-patterned anisotropic substrates are briefly reviewed. The static droplet shape as well as the observed contact angles exhibit unique scaling behavior as a function of the macroscopic wettability, as arising from patterns consisting of alternating hy-drophilic and hydrophobic stripes. In addition, the motion of liquid from surface regions with low macroscopic wettability towards more wetting areas is described. Linear patterns are presented, which induce liquid movement along the chemically defined stripes giving rise to a macroscopic gradient in surface energy. Finally, we show that lattice Boltzmann modeling enables semrquantitatively accurate simulation of the experimental observations.