Contact Angle Meter Research Articles

Anti-bacterial superhydrophobic silver on diverse substrates based on the mussel-inspired polydopamine

Based on the mussel-inspired polydopamine, superhydrophobic silver on diverse substrates of titanium alloy, silicon and polypropylene was successfully fabricated via a facile silver mirror reaction. The surface morphology, surface chemistry, and surface wettability were evaluated by field emission scanning electron microscopy, X-ray photoelectron spectroscopy, and contact angle meter, respectively. The stability of the superhydrophobic state was evaluated by monitoring the contact angle variation for the superhydrophobic sample exposing to air for 60days or contacting with a water droplet in a saturated vapor atmosphere for 70h. Anti-bacterial effect was evaluated using a series of assays, such as the anti-bacterial activity assay according to the Japanese Industrial Standard JIS Z 2801: 2010, the bacterial inhibition ring assay, and the visualization of bacteria on samples by scanning electron microscopy. Experimental results showed that the superhydrophobic state could be retained in the stability test, and the superhydrophobic silver exhibited strong anti-bacterial ability against Escherichia coli and Staphylococcus aureus due to the releasing of Ag+ bactericide and the superhydrophobicity.

Slippery liquid-infused porous surface bio-inspired by pitcher plant for marine anti-biofouling application

Marine biofouling, caused by the adhesion of microorganism, is a worldwide problem in marine systems. In this research work, slippery liquid-infused porous surface (SLIPS), inspired by Nepenthes pitcher plant, was constructed over aluminum for marine anti-biofouling application. The as-fabricated SLIPS was characterized with SEM, AFM, and contact angle meter. Its anti-biofouling performance was evaluated with settlement experiment of a typical marine biofouling organism Chlorella vulgaris in both static and dynamic conditions. The effect of solid substrate micro-structure on anti-biofouling property of SLIPS was studied. It was suggested that the micro-structure with low length scale and high degree of regularity should be considered for designing stable SLIPS with exceptional anti-biofouling property. The liquid-like property is proven to be the main contributor for the exceptional anti-biofouling performance of SLIPS in both static and dynamic conditions. The low roughness, which facilitates removing the settled C. vulgaris under shear force, is also a main contributor for the anti-biofouling performance of SLIPS in dynamic condition.

Surface characteristics and adhesive strength to epoxy of three different types of titanium alloys anodized in NaTESi electrolyte

Three different types of titanium alloys (near-alpha, near-beta and alpha–beta) were anodized in NaTESi electrolyte to compare the surface characteristics and adhesive strength between the anodic oxide nanostructures and the epoxy resin. FESEM, XRD and EDS were used to evaluate the morphology and crystalline structure of the anodic oxide films. The wettability and roughness of the anodic oxide films were measured using a contact angle meter and a digital video microscope. The correlation between the adhesive strength, surface morphology, phase composition, roughness and wettability of three different types of anodic oxide films is discussed in detail. The results showed that a uniform, dense oxide film was formed on the TA15 samples and a micro-protrusion with pore oxide film was formed on the TB8 samples, whereas an easily dissolved oxide film with large-scale pits was formed on the TC4 samples. The maximum shear strengths of TA15 (15.5MPa), TB8 (19.2MPa) and TC4 (17.6MPa) were obtained after they were anodized at 20V, 15V and 10V, respectively. The wettability of the anodic oxide films increased with increasing voltage and a notable increase of the roughness is obtained after anodization. The TB8, which is of the near-beta titanium alloy type can provide a better surface topography for adhesion.

Effect of titanium nitride coating on physical properties of three-dimensional graphene

In this paper, titanium nitride (TiN) was applied on the surface and into the porous structure of three-dimensional graphene (3DG) by chemical method. This method consists of immersing 3DG into a solution containing Ti ions and annealing under ammonia atmosphere at 850°C. The effects of TiN coating and high temperature annealing under NH3 on the physical properties of 3DG were investigated. For this purpose, the 3DG samples, with and without TiN coating, were characterized via XRD, SEM, XPS, and Raman spectroscopy. Then, the electrical resistivity, work function, and wettability of samples were determined by Van der Pauw method, contact angle meter, and UV photoelectron spectroscopy (UPS), respectively. The results showed that an almost pure and very crystalline TiN phase with titanium/nitrogen atomic ratio of 1.09 was formed on the 3DG network. Annealing of 3DG under NH3 resulted in locally doping of graphene with nitrogen and generation of defects in its structure. After TiN coating, the work function value of 3DG (5eV) was reduced to 4.68eV, while its initial water contact angle decreased from 127° to 83°.

Electrochemical characterization and in-vitro bio-assessment of AZ31B and AZ91E alloys as biodegradable implant materials.

The degradation of magnesium alloys, AZ31B and AZ91E, are under review due to a their ability to degrade under physiological conditions and successively yield an oxidized biocompatible by-product which can safely be absorbed by the body. By exploiting the biodegradability of magnesium alloys, the prospects of developing an unprecedented class of implant are at hand. To do so however, the rate of corrosion of the alloys must be modified in order to better suit physiological conditions. Therefore, anodization was carried out on AZ31B and AZ91E specimens to alter the surface chemistry to reduce the corrosion rates and improve biocompatibility. Scanning electron microscopy, energy dispersive spectroscopy, atomic force microscopy and contact angle meter, were used to characterize and compare the surfaces of untreated and anodized magnesium alloys. Corrosion behavior was evaluated by electrochemical tests using potentiodynamic polarization and electrochemical impedance spectroscopy, to verify changes in corrosion rates as a result of anodization. Finally, a bio-assessment using MTS assays and fluorescent microscopy were carried out to ensure that the anodization process had no compromise on the biocompatibility of the magnesium alloys. The study indicated that the anodization process did alter the surface chemistry of the alloys, yielding slower corrosion rates, while causing no adverse effects in regards to biocompatibility.

Biomimetic fabrication of polymer film with high adhesive superhydrophobicity by duplicating locust wing surface

Locust is a common flying insect. Locust wings were used as biomimetic templates to fabricate multi-functional polymer(polydimethylsiloxane, PDMS) films by soft lithography. The microstructure and wettability of the natural and artificial locust wing surfaces were investigated by means of a scanning electron microscope(SEM) and a video-based contact angle meter. The natural locust wing surface exhibits complicated hierarchical structures and high adhesive superhydrophobicity(contact angle 152°). The prepared polymer film faithfully reproduces the surface microstructures of the bio-template, and displays a good hydrophobicity and high adhesion(contact angle 144°). The complex wettability of the natural and artificial locust wing surfaces ascribes to the cooperative effect of hydrophobic composition and multi-dimensional rough microstructures. This work not only promotes our understanding of the wetting mechanism on bio-surfaces, but offers an inexpensive and effective approach for biomimetic fabrication of multi-functional interfacial materials.

Preparation and characterization of triazinedithiol nanofilm on surface of sintered NdFeB permanent magnet

In this work, an organic nanofilm was directly prepared on the metal (sintered NdFeB permanent magnet) surface by electrochemical polymerizing of functional triazinedithiol compound 6-(n-allyl-1,1,2,2-tetrahydroperfluorodecyl) amino-1,3,5-triazine-2,4-dithiol monosodium. The polymeric nanofilm was characterized by spectroscopic ellipsometry, static water contact angle meter, and atomic force microscopy. The chemical progress of electrochemical polymerization was studied by cyclic voltammetry. The film formation mechanism was investigated via X-ray photoelectron spectroscopy and Fourier transform infrared reflection spectroscopy and the results showed that the thiol groups play an important role in polymerization of the film on the substrate. This research may provide a basis for fabricating a triazinedithiol film on metal surfaces and have a promising future for expanding the application of depositing polymer films on metals.

Improving the Surface Wettability of Parylene C Film by Hyperthermal Hydrogen Induced Cross-Linking Technology

In this paper, we present a new approachcalled hyperthermal hydrogen induced cross-linking (HHIC) technology,which can successfully enhance the surface wettability of Parylene C (PC) film via cross-linking hydrophilic polyacrylic acid（PAA）on its surface. Water Contact Angle Meter and Fourier Transform Infrared Spectroscopy (FTIR) were used to characterize wetting property, surface chemical structureof PC film before or after HHIC treatment,respectively. The results show that PAA with polar functional groups can be successfully grafted onto the PC film. As a result, the water contact angle of the modified PC membrane surface decreased from 84° to 23°,PC membrane surface wettability is improved effectively.

Characteristics of ambient-pressure-dried aerogels synthesized via different surface modification methods

In order to compare the various surface modification methods of ambient-pressure-dried aerogels, three different surface modification methods, namely co-precursor method, derivatization method and two-step method, were studied in this paper. The property differences of the aerogels caused by the three surface modification methods were discussed in terms of the reaction processes, micromorphology, pore size distributions, hydrophobicity and thermal stability. During the surface modification process, organic groups were attached to the wet gel skeletons transforming the hydrophilia to the hydrophobicity which were characterized by Fourier transform infrared spectrometry (FTIR). Though mesoporous structure could be obtained by all the methods, the co-precursor method had the smallest special surface area, pore volume and average pore size, while the derivatization method presented the best uniform pore size distribution with the most probable pore diameter of 7 nm and average pore size of 12 nm. Among the three methods, the samples of the two-step method had the lowest intensity of ≡Si–OH groups which indicated the excellent hydrophobicity, and the contact angle was confirmed as 162° using a contact angle meter. And two exothermic peaks on the DSC curve of the two-step method samples were observed unexpectedly, attributing to the oxidation of organic groups on the aerogel skeletons. Meanwhile, the initial temperatures of the two peaks were both higher than those of the derivatization method which suggested that the thermal stability of the silica aerogels could be improved by the two-step method. From all mentioned above, it can be drawn that surface modification methods had obvious effects on the properties of aerogels.

Tribological properties of self-assembled monolayers prepared on titanium film

The self-assembled monolayers of octadecyltrichlorosilane (OTS) and 1H, 1H, 2H, 2H-perfluorooctyltrichlorosilane (FOTS) were prepared on titanium surfaces, irradiated by ultraviolet irradiation device. Contact angle meter, atomic force microscope and Centre for Tribology (CETR) UMT-2 tribometer were used to explore the surface morphology and tribological properties. The influences of function groups, slide velocity, load and ultraviolet irradiation on tribological properties of samples were analysed. From experiments, it was found that OTS and FOTS SAMs (self-assembled monolayers) prepared on titanium films exhibit hydrophobic and tribological properties, especially under 5-minute ultraviolet irradiation. The frictional force of OTS SAMs is lower than that of FOTS SAMs. The wear time of FOTS SAMs is longer than that of OTS SAMs.

Preparation and characterization of thermoplastic starches and their blends with poly(lactic acid)

Two different thermoplastic starches (TPS), namely maleic anhydride grafted starch (MA-g-starch) and epoxidized cardanol grafted starch (Epicard-g-starch), were successfully prepared by chemical modification without the addition of any plasticizer. The structure and properties were characterized by nuclear magnetic resonance (NMR), X-ray diffraction (XRD), hot press testing, scanning electron microscopy (SEM) and contact angle meter, respectively. Results from XRD showed that the highly crystalline structure of native starch was destroyed after modification. Continuous phase was obtained from both of the chemically modified starches after hot pressing at 130°C, indicating that they have good thermoplasticity. Subsequently, they were melt-blended with PLA. It was found that the Epicard-g-starch had a much finer dispersed phase size than MA-g-starch in PLA matrix due to its better hydrophobicity. As a result, the mechanical properties of PLA/Epicard-g-starch blend were superior to those of PLA/MA-g-starch blend.

A Comparison of the Complex Wettability between Locust and Moth Wing

The microstructure, hydrophobicity and chemical composition of the locust and moth wing surfaces were investigated by a scanning electron microscope (SEM), a contact angle meter and a Fourier transform infrared spectrometer (FT-IR). The hydrophobicity models were established on the basis of the Cassie-Baxter equation. The locust and moth wing surfaces are composed of naturally hydrophobic materials, but exhibit different complex wettability. The locust wing surface is of extremely high adhesion (sliding angle>180°) and superhydrophobicity (contact angle 151.5~157.3°), while the moth wing surface is of low adhesion (sliding angle 1~3°) and superhydrophobicity (contact angle 150.5~155.6°). The complex wettability of the wing surfaces ascribes to the cooperative effect of material element and structural element. The locust and moth wings can be potentially used as biomimetic templates for design and preparation of novel functional interface and no-loss microfluidic transport channels.

Removal of natural organic matter by forward osmosis membrane: Flux behaviour and foulant characterization

Fouling of cellulose triacetate(CTA) forward osmosis(FO) membranes by natural organic matter(NOM) was studied by means of a cross-flow flat-sheet forward osmosis membrane system. The NOM solution was employed as the feed solution(FS), and a sodium chloride solution(3 mol/L) was used for the draw solution(DS). The process was conducted at various temperatures and cross-flow velocities. The flux decline was investigated with 3 h forward osmosis operation. The substances absorbed on the membranes were cleaned by ultrasonic oscillation of the fouled membranes and were characterized by methodologies including fluorescence excitation-emission matrices (EEMs) and liquid chromatography with an organic carbon detector(LC-OCD), and the variations of membrane properties were also investigated by Fourier transform infrared spectrometer(FTIR) and a contact angle meter. It was noted that the rejection efficiency of NOM is remarkable and that ultrasonic oscillation is an effective method to extract the NOM fouled on the CTA membranes after FO process. A higher cross-flow velocity and lower temperature benefit the anti-fouling capacity of the membrane significantly. Although humic substances accounted for the majority of the NOM, aromatic proteins and amino acids were the main fouling components on the membranes, with symbolic FTIR peaks at 2355, 1408 and 873 cm−1. The present surface foulant made the membranes becoming more hydrophilic, as demonstrated by a significant decrease in contact angle(ranging from 20% to 46%) under all the operation conditions.

The Role of Hierarchical Micro-Morphology in the Wetting Property of Moth (Geometrinae) Wing Surface

The micro-morphology of the moth wing surface was characterized by a scanning electron microscope (SEM). The contact angle (CA) and sliding angle (SA) of water droplet on the wing surface were measured by an optical CA meter. The wetting mechanism was discussed from the perspective of biological coupling. The moth wing surface is of superhydrophobicity (CA 143~156°) and low adhesion (SA 1~4°), and displays multiple-dimensional rough micro-morphology. The scales play a crucial role in the complex wettability of the wing. The average rate of CaCO3 pollution removal from the wing surface is as high as 87.3%. There is a positive correlation (R=0.8777) between pollution removal rate and roughness index of the wing. The cooperation of chemical composition and micro-morphology contributes to the special wettability and outstanding self-cleaning performance of the wing. The moth wing can serve as a template for biomimetic design and preparation of novel interfacial material with multi-functions.

Effects of Nano Silver Film on the Hydrophobicity of Moth Wing

The microstructure, superhydrophobicity and chemical composition of the moth wing surface were investigated by a scanning electron microscope (SEM), an optical contact angle (CA) meter and a Fourier transform infrared spectrometer (FT-IR). nanosilver film was coated on the wing surface by vacuum evaporation. The wetting mechanism was discussed from the perspective of biological coupling. The moth wing surface, composed of naturally hydrophobic material, is of high hydrophobicity (CA 143~156°) and exhibits complicated hierarchical micro-morphology including primary structure, secondary structure and tertiary structure. The cooperation of hydrophobic material and rough micro-morphology leads to the high hydrophobicity of the wing surface. The wing surfaces coated with 50~1000 nm silver films are still hydrophobic (CA > 110°). The multiple-dimensional rough structure of the wing surface results in the transition of metal silver from hydrophilic to hydrophobic. The moth wing can serve as a bio-template for design and preparation of micro-controllable superhydrophobic surface.

Preparation and micro-tribological property of hydrophobic organic films on the surface of Mg–Mn–Ce magnesium alloy

Two different organic compounds with a same terminal group octadecyl were used to prepare two kinds of hydrophobic organic ultrathin films on the surface of Mg–Mn–Ce alloy. The OTS film was prepared by self-assembling of the n-octadecyltrichlorosilane (OTS), and STN film was prepared by polymer-plating of another octadecyl compound 6-stearylamino-1,3,5-triazine-2,4-dithiol monosodium (STN). The surfaces were characterized by X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR), scanning probe microscopy, and contact angle meter. The results showed that the adhesion force at nano scale was reduced from 12.35 nN for substrate to 5.76 nN for STN film and 4.12 nN for OTS film. Besides, the nano friction force and coefficient also effectively reduced by modification of STN and OTS film on Mg–Mn–Ce alloy. Thus, hydrophobic organic films provide an effective approach to solve nano-tribological issues. Furthermore, it was also found that the differences of the friction properties between the two films were attributed to the structure of the head groups bonded to the substrate.

Study on Preparation and Surface Properties of Fluorinated Acrylate Hydrophobic Polymer Film

A new fluorinated acrylate terpolymer hydrophobic polymer was prepared by emulsifier-free inverse microemulsion polymerization using methyl methacrylate (MMA) and hexafluorobutyl acrylate (HFBA) as monomers, and methyl polyethylene glycol methacrylate (MPEGMA) as polymerizable emulsifier. Membrane properties were characterized by means of FT-IR, SEM and Contact Angle Meter. The effect of fluorinated monomer content, water content in the inverse precursor microemulsion on the surface morphologies and hydrophobicity of the polymer film was mainly discussed. Morphological studies of the fluorinated polyacrylate polymers by SEM showed that discrete granular microstructures were obtained from precursor microemulsion with higher water content. On the other hand, smooth and continuous surface morphologies were found with lower water content. Contact angle revealed that the fluorine preferentially enriched at the film-air interface and more hydrophobic that the film-glass interface. The amount of HFBA had significantly effects on the film properties. The water contact angle of the film-air interface increased as the amount of HFBA increased from 0 ml to 4 ml and then remained almost unchangeable. The film formed from the fluorinated polyacrylate polymer with higher water content in the precursor microemulsion exhibited better hydrophobicity in comparison with the film formed from the fluorinated polyacrylate polymer with the lower water content, and it confirmed that rough surface have high water contact angles.

Corrosion-resistance, robust and wear-durable highly amphiphobic polymer based composite coating via a simple spraying approach

Abstract This study successfully developed a simple spray approach to fabricate a robust highly amphiphobic poly(phenylene sulfide) (PPS)/fluorinated ethylene propylene (FEP)/poly(dimethylsiloxane) (PDMS) composite coating with high-performance in corrosion-resistance, wear-durable through designing the nano/micro two-tier roughness and fluorinating with materials of the low surface free energy. The highly amphiphobic and tribological properties of the coatings were measured by the contact angle meter and the pin-on-disc tribometer, respectively. It was interested to observe that the composite coating showed superhydrophobic and highly oleophobic simultaneously, with the highest contact angles of water, glycerine and ethylene glycol up to 173 ± 2.1°, 142 ± 2.2° and 139 ± 2.1°, respectively. Moreover, the surfaces of the PPS/FEP composite coatings were investigated by means of Fourier transform infrared spectroscopy (FT-IR), X-ray diffractometry (XRD) and energy-dispersive X-ray spectroscopic (EDS). The robust highly amphiphobic coating also showed remarkable durability against strong acid and strong alkali in the pH range from 1 to 14. After 47 h sliding wear test, no failure sign on the PPS/45%FEP/PDMS composite coating was observed. Such unique characteristics were attributed to the synergistic effect of the nano/micro two-tier roughness and fluorinating with low surface free energy groups (–CF 2 –, –CF 3 –).

비용매 휘발법을 이용한 생체모사 혈액친화성 폴리락티드-카프로락톤 공중합체 필름의 제조

혈항혈전성 표면의 제조를 위해 간단한 비용매 휘발 방법을 통하여 고탄성체이면서 생분해성 폴리 락티드-카프로락톤 공중합체 필름의 표면상에 연잎 구조물과 유사한 마이크로 돌기를 만들어 주었다. 표면 구조와 소수성도, 항혈전 효과 등을 시험했으며, 결정화도와 탄성회복률 등의 물리적 특성도 분석하였다. 그 결과 비용매와 메틸렌클로라이드의 혼합 부피비 1:2에서 연잎표면과 유사한 최적의 효과를 얻었으며, 이때 수접촉각은 <TEX>$124^{\circ}$</TEX>였다. 혈소판 부착시험에서는 처리하지 않는 군에 비해 약 10%만 부착되는 효과를 확인할 수 있었다. Simple poor-cosolvent casting was used to surface treat biodegradable elastic poly(L-lactide-co-<TEX>${\varepsilon}$</TEX>-caprolactone) (PLCL; 50:50) copolymer films that presented lotus-leaf-like structures. We evaluated whether the lotus-leaflike-structured PLCL (L-PLCL) films could be used as a biomaterial for artificial vascular grafts. The surface morphology, hydrophobicity, and antithrombotic efficiency of the films were examined while immersed in platelet-rich plasma (PRP) using scanning electron microscopy (SEM) and a contact angle meter. The recovery and crystallinity of the films were measured using a tensile-strength testing machine and an X-ray diffractometer, respectively. The solvent containing acetic acid, as a poor co-solvent, and methylene chloride mixed in a 1:2 ratio produced an optimal PLCL film with a water contact angle of approximately <TEX>$124^{\circ}$</TEX>. Furthermore, the surface of the L-PLCL films immersed in PRP showed a lower rate of platelet adhesion (<10%) than that of the surface of an untreated PLCL film immersed in PRP.

Development of Superhydrophobic Surface for Medical Textiles

The objective of this study was to fabricate superhydrophobic surface with superhydrophobic property using nanoparticles and water-repellent agents for medical textiles. The wettability of the super hydrophobic surface was compared to that of other materials having a variety of roughness and surface energy. Microstructures were fabricated with 100% PET textiles having various yarn thickness and yarn finishing. Nano-sized structures were fabricated by finishing the PET textiles with CNTs nanoparticles using water-repellent agent. Contact angle (CA), contact angle hysteresis and shedding angle analysis were evaluated by Theta Lite contact angle meter (attension, Finland). Also, breathable waterproof properties were measured by water vapor transmission rate (ASTM 96-CaCl2) and air permeability (ISO 9237-1995). The results indicate that the super hydrophobicity was strongly influenced by the binary structure having nano-scaled roughness than by the chemical composition of surface. It was proven that the shedding angle, the angle at which a water droplet rolls off the surface, was reasonable method to analysis the super hydrophobic properties. Also, it was shown that all of the water-repellent agents and nano-particles did not decrease air permeability and water vapor transmission rate noticeably. The DTY sample treated with CNTs exhibited the highest super hydrophobic properties, having static contact angle of 160° and shedding angle of 4.4°. These results indicated that the long nanofiber shape of carbon nano tubes successfully maintained the trapped micro sized air layers like a papillae of lotus leaf.