Surface Modification Process Research Articles

A review on friction stir processing over other surface modification processing techniques of magnesium alloys

An enormous amount of research has been conducted on aluminium alloys in friction stir processing (FSP), despite magnesium alloys reporting severe weight reduction when compared to aluminium alloys; a very slight amount of research has testified for FSP of magnesium alloys. Magnesium is highly reactive and susceptible to corrosion in the presence of an aggressive environment. This highly corrosive nature of magnesium limits its applications. Surface properties like crystal structure, composition, and microstructure influence the corrosion and wear properties of the material. Coating techniques and alloying techniques like laser surface modifications are performed to passivate the magnesium surface from corrosion. Coating techniques, however, have been found to be insufficient in corrosion protection due to coating defects like pores, cracks, etc, adhesion problems due to poor surface preparation of the substrate, and impurities present in the coating which provide microgalvanic cells for corrosion. The current study gives a detailed overview of different types of surface modification methods, such as physical vapour deposition, chemical vapour deposition, chemical conversion coating, and ion implantation coating techniques, and also focuses on a few alloying or surface processing methods, such as laser surface modification – namely laser surface melting, laser surface cladding, laser shot peening, laser surface alloying and FSP. FSP is a novel surface modification method derived from friction stir welding, which modifies the microstructure and composition of surface layer without changing the bulk properties to enhance corrosion resistance. FSP enhances and homogenizes the microstructure but also eliminates the breakup of the brittle-network phases and cast microstructure imperfections. Indeed, FSP can produce particle and fibre-reinforced magnesium-based surface composites. FSP empowers the manufacturing of magnesium by adding additives. The different methods of coating and surface modification are compared with FSP.

Review on porous materials for the thermal stabilization of proteins

Proteins, the key components of vaccines, enzymes and many types of therapeutics, are sensitive to denaturing and loss of structure when exposed to high temperatures. One way to thermally stabilize proteins is through immobilization on a porous support. In this review, a comparative analysis of the literature reports on the most relevant porous materials for protein thermal stability is presented. The materials fall into two main categories: inorganic porous materials and organic polymer materials. Inorganic porous materials for protein immobilization include metal oxides (e.g., aluminum oxides, and iron oxides), silicon dioxides, activated carbons and metal organic frameworks. Organic polymer materials include both natural and synthetic polymers, with natural polymers (e.g., agarose, chitosan and alginate) being by far the most widely studied type of material for enzyme immobilization. Support materials, support surface chemical modification agents, and degree of thermal stability are discussed in detail. The review may be helpful in selecting the optimum support material and surface modification process for a given protein to increase thermal stability. • Comprehensive review on thermal stabilization of proteins on porous materials with 166 sources from 1955 to the present. • Applications discussed include catalyst immobilization, vaccine and protein therapeutic thermal stability and drug delivery. • Inorganic and organic porous materials mentioned. • Includes silicas, activated carbons, aluminum oxides, iron oxides, metal organic frameworks, natural and synthetic polymers. • Includes over 60 biomolecules consisting of proteins, enzymes and vaccine conjugates.

Recent Advancements in Polyphenylsulfone Membrane Modification Methods for Separation Applications.

Polyphenylsulfone (PPSU) membranes are of fundamental importance for many applications such as water treatment, gas separation, energy, electronics, and biomedicine, due to their low cost, controlled crystallinity, chemical, thermal, and mechanical stability. Numerous research studies have shown that modifying surface properties of PPSU membranes influences their stability and functionality. Therefore, the modification of the PPSU membrane surface is a pressing issue for both research and industrial communities. In this review, various surface modification methods and processes along with their mechanisms and performance are considered starting from 2002. There are three main approaches to the modification of PPSU membranes. The first one is bulk modifications, and it includes functional groups inclusion via sulfonation, amination, and chloromethylation. The second is blending with polymer (for instance, blending nanomaterials and biopolymers). Finally, the third one deals with physical and chemical surface modifications. Obviously, each method has its own limitations and advantages that are outlined below. Generally speaking, modified PPSU membranes demonstrate improved physical and chemical properties and enhanced performance. The advancements in PPSU modification have opened the door for the advance of membrane technology and multiple prospective applications.

Assessment of the Impact of the Surface Modification Processes of Cotton and Polyester Fabrics with Various Techniques on Their Structural, Biophysical, Sensory, and Mechanical Properties.

This article presents research on the assessment of the impact of surface modification of cotton and polyester fabrics using four techniques (flocking, layer by layer, screen printing and thermal-transfer printing) on their structural, mechanical, biophysical, and sensory properties. Depending on geometry and raw materials of the fabrics, the clothing made of them it is characterized by certain biophysical properties which are intended to protect the human body against external factors, but also against excessive sweating and overheating or cooling down. The aforementioned properties of the modified textiles were determined with: optical microscopy, microcomputed tomography, a tensile testing machine, sweating guarded-hotplate, air permeability tester, and the Kawabata evaluation system. Based on analysis of obtained results, it can be concluded that flocking reduces air permeability the most (−77% for cotton fabric and −99.7% for polyester fabric), and total hand value (−58% and −57%) and increases water vapor resistance the most (+769% and +612%) while the screen printing increases the thermal resistance the most (+119% and +156%) compared to unmodified textiles. It can be concluded that, when modifying textile substrates, the area of modification and their size on clothing products should be carefully selected so as not to adversely affect the feelings of potential wearers.

Comparative Study on Extraction of Cellulose Fiber from Rice Straw Waste from Chemo-Mechanical and Pulping Method.

Inspired by nature, cellulose extracted from plant wastes has been explored, due to its great potential as an alternative for synthetic fiber and filler that contributes to structural performance. The drive of this study was to extract, treat, and evaluate the characteristics of rice straw (RS) (Oryza sativa L.) cellulose as a biodegradable reinforcement to be utilized in polymer base materials. Two routes of extraction and treatment were performed via the pulping (Route 1) and chemo-mechanical methods (Route 2), in order to discover comparative characteristics of the synthesized cellulose fiber. Comprehensive characterization of RS cellulose was carried out to determine crystallinity, surface morphology, and chemical bonding properties, using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and Fourier transform infra-red (FTIR), respectively. The XRD test results showed that the crystallinity index (CI) of cellulose powder (CP) decreased after the surface modification treatment, Route 2, from 64.50 to 50.10% CI for modified cellulose powder (MCP), due to the surface alteration of cellulose structure. From Route 1, the crystallinity of the fibers decreased up to 33.5% (dissolve cellulose, DC) after the pulp went through the surface modification and dissolution processes, resulting from the transformation of cellulose phase into para-crystalline structure. FESEM micrographs displayed a significant reduction of raw RS diameter from 7.78 µm to 3.34 µm (treated by Route 1) and 1.06 µm (treated by Route 2). The extracted and treated cellulose via both routes, which was considerably dominated by cellulose II because of the high percentage of alkaline used, include the dissolve cellulose (DC). The dissolution process, using NMMO solvent, was performed on the pulp fiber produced by Route 1. The fiber change from cellulose I to cellulose II after undergoes the process. Thus, the dissolution process maintains cellulose II but turned the pulp to the cellulose solution. The acquired characteristics of cellulose from RS waste, extracted by the employed methods, have a considerably greater potential for further application in numerous industries. It was concluded that the great achievement of extracted RS is obtained the nanosized fibers after surface modification treatment, which is very useful for filler in structural composite applications.

A Two-Step Approach to Tune the Micro and Nanoscale Morphology of Porous Niobium Oxide to Promote Osteointegration.

We present a two-step surface modification process to tailor the micro and nano morphology of niobium oxide layers. Niobium was firstly anodized in spark regime in a Ca- and P-containing solution and subsequently treated by acid etching. The effects of anodizing time and applied potential on the surface morphology is investigated with SEM and AFM, complemented by XPS compositional analysis. Anodizing with a limiting potential of 250 V results in the fast growth of oxide layers with a homogeneous distribution of micro-sized pores. Cracks are, however, observed on 250 V grown layers. Limiting the anodizing potential to 200 V slows down the oxide growth, increasing the anodizing time needed to achieve a uniform pore coverage but produces fracture-free oxide layers. The surface nano morphology is further tuned by a subsequent acid etching process that leads to the formation of nano-sized pits on the anodically grown oxide surface. In vitro tests show that the etching-induced nanostructure effectively promotes cell adhesion and spreading onto the niobium oxide surface.

Study of oleic acid as a surface modifying agent for oxide nanoparticles

The development of nano lubricants has increased rapidly in recent years. With the addition of nano-additives to conventional oils to enhance tribological properties, the stability of nanoparticles remains a challenge, which can be ruled out with the help of surface modification of nanoparticles. So, oxide nanoparticles (Al2O3, CuO, and SiO2) are analyzed in this study. The morphology of the nanoparticles is analyzed with the aid of a high-resolution field-emission scanning-electron microscope (HR FESEM) and found to be nearly spherical. The surface modification process is done with the help of oleic acid (OA). The surface modification process parameters are thoroughly discussed. The Fourier transform infrared spectroscopy (FTIR) result shows prominent oleic acid capping on oxide nanoparticles.

Optimization of friction surfaced deposits of aluminium alloy 6068 over low carbon steel

Friction surfacing is a surface modification process by using friction. All the researchers and industrialist are concentrating in this area as there are no fumes and spark is involved during the process, can be automated and regulated easily. Hence all conventional process can be replaced. The studies were carried out to create a friction coating on the surface of a low carbon steel substrate using aluminium alloy 6068 and friction surfacing. The effects of three parameters on width and height were determined: frictional pressure, mechtrode speed in rpm, and welding transverse speed. The defect free friction deposited surfaces were confirmed through visual, metallurgical and bend test. Out of these three factors welding speed was found the most dominating factor. The linear regressions were established for the two responses viz. deposited width and deposited height. To optimize the responses Taguchi’s three factors and two level designs was used.

ПОРІВНЯЛЬНИЙ АНАЛІЗ РОЗМІРНИХ ХАРАКТЕРИСТИК ЧАСТИНОК ГІБРИДНИХ ТА МІНЕРАЛЬНИХ АДСОРБЕНТІВ ДЛЯ ПРОЦЕСІВ ВОДООЧИЩЕННЯ

n the work, a comparative morphometric analysis of various types of domestic adsorbents intended for use in water purification technologies is performed. Four types of adsorbents were investigated: «Möbius» carbon adsorbent, P1T1KA clay powder of the montmorillonite type, DG-100 carbon black, C-1 colloidal graphite preparation.Morphometric analysis of adsorbent particles was carried out by the method of optical polarization microscopy («Bi-olam» brand microscope). Photomicrographs of particles pre-dispersed in the immersion liquid were obtained using a digital camera with a high-resolution matrix. Quantitative assessment of the sizes of adsorbent particles was carried out by the method of digital image analysis (ImageJ software package). The area and perimeter of individual particles were determined and their equivalent diameter and shape index were calculated. Statistical processing of experimental data was carried out using the «Statistica» software package.It was established that the nature of the distribution of particles of the investigated types of adsorbents in terms of equiv-alent diameter depends on the type of sample, and may be complicated by the processes of particle aggregation.It is shown that a similar nature of distribution is observed for all investigated carbon adsorbents according to the shape index. The pronounced and largest fraction (27-37%) corresponds to particles with a shape close to round. The most acceptable adsorbents for water purification processes can be considered a colloidal graphite preparation and clay powder of the mont-morillonite type, for which there is a higher homogeneity of the distribution of particles according to the shape indicator. This, in turn, can provide higher sorption efficiency in water treatment technologies.The application of the method of optical polarization microscopy in combination with the morphometric analysis of particles makes it possible to reasonably approach the selection of the brand of adsorbents for their use in water purification technologies. Further research in this direction can be directed to the processes of surface modification of adsorbent particles to increase their specific capacity and selective ability.

Ti6Al4V Surface Modification Techniques to Modulate Bone Cell Response: A Review

Biomaterial-tissue interactions are known to largely affect implant performance, relating to alteration of physiological processes. Within this context, metals continue to have a major role as most implants contain at least one metallic part. In particular, titanium alloys are of pivotal importance in orthopedics and dentistry. Being osteointegration somewhat affected by implant surface conditions, surface modification qualifies as a way to modulate tissue response, net of an effective design of the whole implant. Currently, a lack of full understanding on the direction to be taken for proper techniques and process conditions to be employed, for the regulation of osteointegration, can be recognized; this happens as a result of the inherent complexity involving host response, implant location as well as its surface chemistry, topography, stiffness and so on. This short review focuses on one of the most used titanium alloys, namely Ti6Al4V. An overview of viable surface modification processes studied in view of bone cell response, as a way to predict implant performance, will be provided, together with the most recent research findings towards a new generation of biomedical implants.

Generation and Characterization of Cold Atmospheric Pressure Plasma Jet for Surface Modification of High-Density Polyethylene

Cold atmospheric pressure plasma technology has a variety of applications in different fields including material science and biomedical science. It has been using for surface modification and material processing in material science and used to improve the wettability, adhesion and biocompability of polymeric surfaces without altering the entire bulk properties. This paper outlines the characterization of cold atmospheric pressure plasma jet, which was generated in a high frequency (20 kHz) and high voltage (3.5 kV) power supply, as well as its application in the surface modification of high density polyethylene. Electrical and optical characteristics are used to estimate the electron density of the plasma. The effect of plasma on the surface properties of the material are analyzed by calculating contact angle, surface energy measurements and analyzing scanning electron microscopy images. Adhesive bonding strength and numerous other attributes have increased, however surface treatment is the process of cleaning, etching, functionalizing, and chemically treating substrates to improve roughness and adhesive properties on the surface. Cold plasma can induce a soft roughening on the surface through ion bombardment with polar functional groups resulting in the decrease in water contact angle.

Reducing the Specular Properties of Metalized Teflon Coverings on Canadian Mobile Servicing Station on the International Space Station

A surface modification process was developed for the metalized Teflon coverings used for thermal protection of electronic equipment on the International Space Station [1]. The developed modification process of Teflon surfaces reduced substantially the specularity of Ag-Inconel coated Teflon thermal control films by changing the morphological appearance of their surfaces by ion-beam texturing in a controlled manner from a metallic-like and shiny to complete milky, white appearance without significantly affecting the thermal optical properties.
 A number of space hardware units covered with the textured Silver-Teflon were exposed to the open space environment between June 2002 and June 2006 and delivered back to Earth at the end of 2006. Remarkable performance was demonstrated by the treated Ag/Teflon, with the solar absorptance and total emittance values and the α/ε ratio remaining very close to the original values as measured before the flights [2].
 In an attempt to protect further the textured surfaces of Teflon from possible erosion by atomic oxygen and VUV in LEO environment, an additional novel surface modification process was developed that created an SixOyCzFn type of structure on the treated surface. The textured Teflon samples before and after surface treatments were tested in a space simulator facility under a combined atomic oxygen/vacuum ultraviolet exposure. A number of advanced characterization techniques were used to evaluate the properties of the modified films [3].

Water Repellency/Proof/Vapor Permeability Characteristics of Coated and Laminated Breathable Fabrics for Outdoor Clothing

This study examined the water repellency (WR), waterproof, and water vapor permeability (WVP) characteristics of twelve types of laminated and coated woven fabrics for outdoor clothing. These characteristics were compared with the fabric structural parameters, such as cover factor, thickness, and weight, and surface modification (finishing) factors, such as coating, laminating, and Teflon treatments. In addition, an eco-friendly process for surface modification was proposed followed by a summary. Superior waterproof-breathable characteristics with 100% water-repellency were achieved in specimen 3 in group A by treatment with a hydrophilic laminated finish using nylon woven fabric with a cover factor between 0.7 and 0.9 in a 2.5-layered fabric, which was the best specimen with waterproof-breathable characteristics. A high WVP in the coated and laminated fabrics was observed in the fabrics with a low weave density coefficient (WDC) and low thickness per unit weight of the fabric, whereas superior water repellency and waterproof characteristics were observed in the high-cover-factor (WDC) fabric with appropriate fabric thickness. The determination coefficient (R2) from regression analysis between the WVP and fabric structural parameters indicated a higher contribution of the fabric structural parameters than surface modification factors, such as coating and laminating to the WVP in the coated and laminated fabrics. Furthermore, the cover factor was the most important factor influencing the WVP of the waterproof-breathable fabrics. Of twelve coated and laminated fabrics, the laminated nylon and nylon/cotton composite fabrics showed superior WVP with high WR and waterproof characteristics. Accordingly, based on the WR, waterproof, and WVP characteristics of the coated and laminated breathable fabrics, the laminating method, as an eco-friendly process, is recommended to obtain better waterproof-breathable fabrics.

Highly efficient Cr(VI) remediation by cationic functionalized nanocellulose beads

Applications of nanocellulose as a water treatment material are being actively pursued based on its interesting properties, such as renewability, large specific surface area, hydrophilic surface chemistry, and biodegradability. This study used carboxymethyl cellulose nanofibrils (CMCNFs) to prepare a typical bead-type adsorbent with improved structural stability as an actual water treatment restoration material. In addition, a cationized nanocellulose adsorbent was prepared by introducing polyethyleneimine (PEI) on the surface of the CMCNF (P/CMCNF), the removal efficiency of Cr(VI) was evaluated, and its mechanism was elucidated. As a result, the P/CMCNF beads showed an excellent Cr(VI) removal capacity of 1302.3 mg/g, the best result among cellulose-based adsorption materials. Cr(VI) was effectively removed by electrostatic attractions combined with chemical reduction and chelation mechanisms. Furthermore, the macrobead fabrication and PEI surface modification process improved the underwater stability of the P/CMCNF, and it showed excellent reuse efficiency.

Robust and scalable production of emulsion-templated microparticles in 3D-printed milli-fluidic device

Emulsions are ideal templates for preparation of functional microparticles in food, cosmetics, and pharmaceutics. However, the lack of a simple and robust platform that allows mass production of oil-in-water (O/W) emulsions has been considered as a practical hurdle for broader applicability of these emulsion-based technologies. Herein, we report a novel 3D-printed milli-fluidic device (3D-PMD) for robust and scalable production of water-in-oil (W/O) as well as O/W emulsions. By using an additive manufacturing method with one-step prototyping capability, 3D-PMD integrates an array of 40 drop-makers with a 3D void geometry and a flow distributor in a compact fashion, which has been difficult to achieve using conventional methods. Experimental results as well as the computational fluid dynamics simulation confirm the validity in the design of the drop-maker and the flow distributor, as well as the hydrophilic surface modification process for the robust and controllable production of poly(ethylene glycol) microgels and polycaprolactone microparticles, prepared from W/O and O/W emulsions, respectively. We anticipate that the simplicity, low-cost ($150/per device), facile manufacturability, and versatile emulsion production capability of our 3D-PMD method offers a unique route to produce W/O and O/W emulsions in a robust and in a scalable manner, providing new and exciting opportunities in various applications involving functional microparticles such as cosmetic products, optical displays, controlled reactions, and drug delivery systems to name a few.

On Force–Displacement Characteristics and Surface Deformation in Piezo Vibration Striking Treatment

Abstract This paper presents an experimental study on a novel mechanical surface treatment process, namely piezo vibration striking treatment (PVST), which is realized by a piezo stack vibration device installed on a computer numerical control (CNC) machine. Unlike other striking-based surface treatments, PVST employs non-resonant mode piezo vibration to induce controllable tool strikes on the workpiece surface. In this study, an experimental setup of PVST is implemented. Four types of experiments, i.e., tool-surface approaching, single-spot striking, one-dimensional (1D) scan striking, and 2D scan striking, are conducted to investigate the relationships among the striking force, tool vibration displacement, and surface deformation in PVST. The study shows that PVST can induce strikes with consistent intensity in each cycle of tool vibration. Both the striking intensity and striking location can be well controlled. Such process capability is particularly demonstrated by the resulting texture and roughness of the treated surfaces. Moreover, two linear force relationships have been found in PVST. The first linear relationship is between the striking force and the reduction in vibration amplitude during striking. The second one is between the striking force and the permanent indentation depth created by the strike. These linear force relationships offer the opportunity to realize real-time monitoring and force-based feedback control of PVST. This study is the first step toward developing PVST as a more efficient deformation-based surface modification process.

High-efficiency black silicon tunnel oxide passivating contact solar cells through modifying the nano-texture on micron-pyramid surface

Optical loss is a significant factor restricting the conversion efficiency of conventional bifacial tunnel oxide passivating contact (TOPCon) solar cells. Black silicon structure is commonly used to enhance the photogenerated current density ( J ph ) of crystalline solar cells due to its excellent light-trapping capability. However, the photogenerated current gain is cancelled by the increased emitter recombination current originated from the black silicon structure with a high enhanced surface area ratio. In this work, we used a buffered oxide etching solution to modify the surface morphology of nanopore/micron-pyramid composite (NPP) structure silicon. Further, we studied the effects of NPP structures with different enhanced surface area ratio on front-side reflection, boron atom doping, emitter passivation, and cell performance. By identifying the appropriate surface modification processing, we fabricated the large-scale (158.75 mm × 158.75 mm) bifacial TOPCon solar cells using industrial equipment and processes with an average short-circuit current density of 41.12 mA/cm 2 and average conversion efficiency of 23.08%. Through adequately widening nanostructure size and depositing high-quality Al 2 O 3 /SiN x stacked passivation films on NPP structure surface, we achieved lower carrier recombination while maintaining high J ph . • Conversion efficiency of 23.2% achieved by b-Si TOPCon solar cells. • Surface modification of b-Si improves emitter passivation using buffer etching. • Medium specific area of b-Si achieve a balance of light-trapping and electrical loss.

Effect of ultrasonic nanocrystalline surface modification process on fretting wear behavior of laser surface textured 20CrMoH steel

Laser surface texturing (LST) followed by ultrasonic surface rolling (USR) was applied to 20CrMoH steel to improve the friction and wear behavior. In this paper, the fretting friction and wear mechanisms of the modified (USR, LST + USR) 20CrMoH steel under different loads and lubrication conditions were systematically investigated. Results indicated that the regular coupling distribution of micro-texture and gradient nanostructure (GNS) was formed on the surface layer of the combined treated material. Simultaneously, the depth of the GNS was up to 22 μm and the surface microhardness was increased from 800 HV0.2 to 860 HV0.2. Besides, the surface roughness Ra value was decreased from 0.24 μm to 0.01 μm and the maximum residual compressive stress (RCS) value was −610 MPa. Under dry friction and high load conditions, compared with the untreated specimen, the average friction coefficient and worn losses of the combined treated specimen were reduced by about 10% and 30%, respectively. In comparison with the untreated specimen, the average friction coefficient of the combined treated specimen was decreased by 26% under the conditions of low load and oil lubrication. Especially, the fretting wear resistance was obviously improved and its worn loss was significantly reduced by 92.05% compared with the untreated material. The predominant wear mechanisms of the combined treated material under dry friction and oil lubrication were oxidation wear and abrasive wear, respectively.

Surface modification of carbon fiber as a protective strategy against thermal degradation

Carbon fibers were surface modified with acrylate-derived polymers with aromatic side chains, to protect the fiber when exposed to high temperatures.The surface modification process induced a significant increase in tensile strength (23.7%) and tensile modulus (8%), for the benzyl-bearing side chain andretained superior tensile strength (20%) and tensile modulus (7%)after heating to 600 °C. Commercialcarbon fibres gave asignificant decrease in tensile strength and modulus, 7% and 4%, respectively, when exposed to the same conditions. This suggests that the surface modification process provides a protective effect against thermal degradation, with possible application in carbon fibre recycling.The interfacial shear strength (IFSS) showed significant improvementbefore (up to 208%) and after (up to 84%) exposure to high temperatures. Analysis of the carbon fiber surface byXPS suggests that the surface bound polymer becomes more graphitic, potentiallyviathe fusion of the aromatic side chains.

Antithetic superhydrophobic/superhydrophilic surfaces formation by simple gas switching in an atmospheric-pressure cold plasma treatment

The wettability control of surfaces is a significant issue in many industrial fields such as encapsulation, water repellency enhancement, oil recovery, etc. From a practical point of view, to reach the intended surface wettability, it is important for a surface modification process to be low-cost, easily implemented and fast. Therefore, in this work, a facile plasma deposition method is suggested to form surfaces with antithetic wettabilities, i.e. superhydrophobic and superhydrophilic, via simple introduction of additive gases in an atmospheric-pressure plasma generated with argon and hexamethyldisilazane (HMDS). The hydrophobic surface (WCA: 115°) modified by Ar/HMDS plasma is easily switched to superhydrophobic surface (WCA: 160°) by N2 addition and to superhydrophilic surface (WCA: 10°) by O2 addition. From physical and chemical analyses of plasma treated surfaces, a small amount of N2 or O2 gas is shown to dramatically change the surface morphology and chemical composition. Besides, by finely tuning the additive gases flow rates, the surface wettability could be continuously modulated in the whole ∼0° to 160° water contact angle range.