Contact Angle Measurement System Research Articles

The Possibility of Changing the Wettability of Material Surface by Adjusting Gravity.

The contact angle, as a vital measured parameter of wettability of material surface, has long been in dispute whether it is affected by gravity. Herein, we measured the advancing and receding contact angles on extremely low contact angle hysteresis surfaces under different gravities (1-8G) and found that both of them decrease with the increase of the gravity. The underlying mechanism is revealed to be the contact angle hysteresis and the deformation of the liquid-vapor interface away from the solid surface caused by gradient distribution of the hydrostatic pressure. The real contact angle is not affected by gravity and cannot measured by an optical method. The measured apparent contact angles are angles of inclination of the liquid-vapor interface away from the solid surface. Furthermore, a new equation is proposed based on the balance of forces acting on the three-phase contact region, which quantitatively reveals the relation of the apparent contact angle with the interfacial tensions and gravity. This finding can provide new horizons for solving the debate on whether gravity affects the contact angle and may be useful for the accurate measurement of the contact angle and the development of a new contact angle measurement system.

Measurement of contact angle under different gravity generated by a long-arm centrifuge

The contact angle, as a vital measured parameter of wettability of a material surface, is pertinent to adhesion, nucleation, capillary phenomena, and liquid management in space. With the development of space exploration, the relationship between the contact angle and gravity has attracted increasing attention. In this study, we designed and manufactured a long-arm centrifuge (d =6 m) and a matched low-rate dynamic contact angle measurement system, which has the capacity to measure the advancing and receding contact angles of sessile drops under 1G-8G. The advancing and receding contact angles of water on smooth and rough surfaces were measured, and the results showed that 1) this apparatus is reliable for measuring the advancing and receding contact angles of sessile drops under 1G-8G, 2) the contact angle is not changed by gravity, while the measured apparent contact angles are changed by gravity owing to they are slope angles of liquid-vapor interface away from the solid surface due to limitation of the resolution of measurement system, and 3) wetting state of the rough surface can be changed by gravity.

Hydrothermal synthesis and characterization of multifunctional ZnO nanomaterials

Multifunctional ZnO nanomaterials are synthesized by hydrothermal method for protective coating and antimicrobial applications. Different nanostructures of ZnO are achieved by controlling the pH of the growth solution in the range 3–11 (acidic to alkali). ZnO nanostructures of different pH value are evaluated for hydrophobic property using static contact angle measurement system and antibacterial activity on gram negative bacteria. Among all morphologies grown at different pH values, ZnO nanorods show superhydrophobic nature. In order to understand the interaction and effect of ZnO nanomaterials on bacterial cell, FESEM study is carried out with microbial cells treated at 1% nanomaterial concentration.

The Role of DC Biased Plasma Treatment of Polystyrene on the Formation of the C≡N Functional Group Controlling Its Hydrophobicity

Nitrogen plasma treatment was carried out to modify the surface of polystyrene film deposited on a quartz crystal microbalance (QCM) sensor. The modification was intended to enhance the wettability of the film by inducing the formation of CN functional group on its surface. This work investigated the effect of DC bias controlling N* in the plasma on the effectiveness of the nitrogen plasma treatment. The polystyrene was deposited by a spin coating method on the surface of a quartz crystal normally used in an electronic resonator. The nitrogen plasma was generated in an aluminium vacuum chamber using a 2 MHz radio frequency (RF) generator. The vacuum pressure and the gas flow rate were kept constant during the experiments. The plasma character in the chamber was controlled by applying a DC bias between the RF electrodes and the sample stage. The DC voltage was varied from 100 to 500 volts at 100 volts’ step, while maintaining the RF voltage constant. During the process, the species in the plasma was characterized using an optical emission spectroscopy (OES). The wettability of the treated samples was tested using a contact angle measurement system. FTIR measurement was utilized to study the polar functional groups on the surface of the polystyrene before and after the treatment. The OES identified the existence of N radical (N*). The reduced intensity of emission line of the N* increased with the increase of the DC voltage. However, a small decrease was also evidence at DC voltage higher than 400 volts. The decrease of the line intensity was directly related to the decrease of the contact angle (CA < 40°). The relation of the N* and the resulted wettability is related to the polar functional group of the C≡N bond found in the treated polystyrene’s surface.

Characterization and Investigation of Biological Properties of Ag-Doped TiO2 Coatings Fabricated on Titanium

In present study, Ag-doped TiO 2 bioceramic coatings were fabricated on cp-Ti by plasma electrolytic oxidation (PEO) and physical vapor deposition (PVD). The phase composition, surface microstructure, elemental composition, surface topography, wettability and chemical state of the PEO and Ag-doped TiO 2 surfaces were characterized by using powder- and thin film-X-ray diffraction (TF-XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), surface profilometer and contact angle measurement system (CAM), respectively. The PEO coating’ surface was porous and rough due to the nature of process. The Ti, anatase-TiO 2 , rutile-TiO 2 and Ag 2 O phases were detected on the Ag-doped PEO surfaces by TF-XRD while The Ti, anatase and rutile phases were obtained on the PEO surfaces. The surface morphology structure of the PEO coating was not changed by PVD process. The Ti, O, P and Ag elements were observed on the Ag-doped PEO surfaces by EDS. Also, the amount of Ag existed on the surface was below cytotoxic limit. The Ag-doped PEO surfaces indicated better hydrophilic character to the PEO surface owing to increasing polarity of the surfaces. In vitro hydroxyapatite-forming ability was evaluated by immersion in simulated body fluid (SBF) at 36.5 ° C for 28 days. The Ag-doped PEO surfaces showed good hydroxyapatite formation ability compared to the PEO surface. The antibacterial activity was evaluated by exposing the samples to Staphylococcus aureus ( S. aureus ) and Escherichia coli ( E. coli ) and they were compared by the reaction of the pathogens to Ag-doped PEO with the PEO controls. The antibacterial ability of the Ag-doped PEO surfaces was significantly improved respect to the PEO surfaces for S. aureus and E. coli .

Properties of Bacterial Cellulose Composites with Silver Nanoparticles

Composites of bacterial cellulose, which were synthesized in a culture of the strain of acetic acid bacteria Komagataeibacter xylinus VKPM B-12068, with silver nanoparticles were produced hydrothermally by varying the concentrations of AgNO3 in the medium. The presence of silver in the composites was confirmed by elemental analysis. An increase in the number of silver nanoparticles in the composite from 1.08 to 9.1 wt % (from 0.044 to 0.370 mg/cm2) was shown under increasing AgNO3 concentration in the medium from 0.0001 to 0.01 M. The structure, properties of the surface, and the physicochemical properties of the composites depending on the silver content were investigated using scanning electron microscopy, differential scanning calorimetry, X-ray diffraction, and a water contact-angle measurement system. Using the disk-diffusion method, it was shown that the resulting composites have a pronounced antibacterial activity against pathogenic microflora E. coli, Ps. eruginosa, and St. aureus.

Low-Cost Contact Angle Measurement System for QCM Sensor

Hydrophobicity is one of the importance factors in the surface properties of materials. This work presents the development of a low-cost contact angle measurement system based on goniometric measurement using a low-cost digital camera, tilt control system for surface alignment and curvature approximation algorithm to determine the contact angle between the solid and spherical cap of a water droplet. The design is specifically targeted for measuring the contact angle of a Quartz Crystal Microbalance sensor in the form of HC-49/U with a disc diameter of 8.7mm.The contact angle measurement using goniometric measurement depends on the quality of captured image and calculation method for the angle determination. Proper alignment of the sample surface is required to minimize the discrepancy of the angle measurement of water drop surface profile caused by gravity. A PIC18F4550 microcontroller is used to control the motorized tilt platform to reduce the discrepancy between left and right contact angle value. Circle fit algorithm to determine the contact angle value from the captured image is used. Using the motorized tilt control system and circle fit algorithm, the developed contact angle measurement system able to measure the contact angle with discrepancy less than 1 O .

Effects of black silicon surface structures on wetting behaviors, single water droplet icing and frosting under natural convection conditions

Abstract In this research, the effects of black silicon and two-stage black silicon surface structures on the characteristics of wetting, icing process of a single water droplet, and frost accumulation under natural convection conditions were investigated. Black silicon and two-stage black silicon surfaces were first designed and fabricated, and then examined by means of scanning electron microscopy (SEM). Wetting behavior was measured by contact angle measurement system. The icing and frosting processes were acquired through high-speed photography. The test surfaces were cooled down from room temperature to well below 0 °C by circulating ethyl alcohol via a constant temperature system. The results show that compared with uncoated silicon, black silicon and two-stage black silicon surfaces can largely increase the surface hydrophobicity, reduce the freezing thickness deformation and show anti-frosting performance. This study provides a new type of hydrophobic surface structure and plays an important role in designing anti-icing/anti-frosting surfaces for practical applications.

Simple and Green Fabrication of a Superhydrophobic Surface by One-Step Immersion for Continuous Oil/Water Separation.

In this paper, stainless steel meshes with superhydrophobic and superoleophilic surfaces were fabricated by rapid and simple one-step immersion in a solution containing hydrochloric acid and stearic acid. The apparent contact angles were tested by a video contact angle measurement system (CA). Field emission scanning electron microscopy (FE-SEM), Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS) were conducted to characterize the surface topographies and chemical compositions. The SEM results showed that mesh surfaces were covered by ferric stearate (Fe[CH3(CH2)16COO]2) with low surface energy. The CA test results showed that the mesh had a maximum apparent contact angle of 160 ± 1.0° and a sliding angle of less than 5.0° for the water droplet, whereas the apparent contact angle for the oil droplet was zero. Ultrasound oscillation and exposure tests at atmospheric conditions and immersion tests in 3.5 wt % NaCl aqueous solution were conducted to confirm the mesh with excellent superhydrophobic and superoleophilic properties. On the basis of the superhydrophobic mesh, a miniature separation device pump was designed to collect pure oil from the oil/water mixture. It showed that the device was easier and convenient. The techniques and materials presented in this work are promising for application to wastewater and oil spill treatment.

Facile fabrication of superhydrophobic silica coatings with excellent corrosion resistance and liquid marbles

Self-cleaning superhydrophobic coatings with water contact angle as high as 156° and sliding angle as low as 3° were prepared through a facile one-step spray coating process by spraying the hydrophobic silica nanoparticles onto Al substrate. In addition, the superhydrophobic coatings maintained excellent electrochemical corrosion resistance in a 3.5 wt% NaCl aqueous solution. The corrosion behavior of the superhydrophobic coatings on the Al substrate was characterized by the polarization curve and electrochemical impedance spectroscopy. The results indicated that the superhydrophobic coatings possessed excellent corrosion resistance. In addition, liquid marbles coated with hydrophobic silica nanoparticles were prepared by gentle rolling of liquid on powder beds of hydrophobic silica nanoparticles. Furthermore, water evaporation from the silica shell with time evolution was investigated using a contact angle measurement system video camera. Superhydrophobic silica surface with excellent corrosion resistance and liquid marbles coated with hydrophobic silica were fabricated by a facile process.

Effect of Electrolyte Concentration on the Surface Properties of Nanoporous TiO2 Layers Formed on Micro-roughened Titanium

The aim of this study was to evaluate the effect of electrolyte concentration on the surface morphology, surface topography, wettability and surface roughness of nanoporous titanium dioxide (TiO 2 ) layers. Titanium (Ti) samples were treated by sandblasting and acid-etching processes. TiO 2 layers were formed on sandblasted/acid-etched titanium in electrolytes containing different HF concentration (% 0.25-2). The samples were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM). The surface roughness and the wettability of the samples were measured using proilometry and a contact angle measurement system. The samples, which were anodized after sandblasting/acid-etching treatment had amorphous structure and peaks from the substrate were observed. The results showed that with increasing HF concentration, the surface morphology of the samples were significantly changed. All the treated samples exhibited hydrophilic properties.

The role of surface energy reducing agent in the formation of self-induced nanoscale surface features and wetting behavior of polyurethane coatings

Abstract The effect of surface energy reducing agent (SERA) on the surface chemistry and physics of the polyurethane (PU) coatings containing 0–10 mol% of SERA was studied. The coatings were carefully analyzed by differential scanning calorimeter, infrared spectroscope, field-emission scanning electron microscope, atomic force microscope and contact angle measurement system. Results indicated that at different concentrations of additive, the SERA segments took different strategies to minimize their interface area with other segments which affected their population on the coating surface. The concentration gradient of SERA segments on the surface of PU led to the creation of a local lateral pressure. The local lateral pressure along with the relative content of solvent showed a synergic effect on the formation of self-induced nanoscale surface features. Contact angle measurements revealed that the role of SERA segments in enhancing the hydrophobicity of PU coatings through creation of specific physical features was more pronounced than through chemical modification of the surface.

The in vitro and in vivo performance of a strontium-containing coating on the low-modulus Ti35Nb2Ta3Zr alloy formed by micro-arc oxidation.

The β-titanium alloy is thought to be a promising alloy using as orthopedic or dental implants owing to its characteristics, which contains low elastic modulus, high corrosion resistance and well biocompatibility. Our previous study has reported that a new β-titanium alloy Ti35Nb2Ta3Zr showed low modulus close to human bone, equal tissue compatibility to a traditional implant alloy Ti6Al4V. In this study, micro-arc oxidation (MAO) was applied on the Ti35Nb2Ta3Zr alloy to enhance its surface characteristics and biocompatibility and osseointegration ability. Two different coatings were formed, TiO2 doped with calcium-phosphate coating (Ca-P) and calcium-phosphate-strontium coating (Ca-P-Sr). Then we evaluated the effects of the MAO coatings on the Ti35Nb2Ta3Zr alloy through in vitro and in vivo tests. As to the characteristics of the coatings, the morphology, chemical composition, surface roughness and contact angle of MAO coatings were tested by scanning electron microscopy, energy dispersive spectroscopy, atomic force microscopy, and video contact-angle measurement system respectively. Besides, we performed MTT assay, ALP test and cell morphology-adhesion test on materials to evaluate the MAOed coating materials' biocompatibility in vitro. The in vivo experiment was performed through rabbit model. Alloys were implanted into rabbits' femur shafts, then we performed micro-CT, histological and sequential fluorescent labeling analysis to evaluate implants' osseointegration ability in vivo. Finally, the Ca-P specimens and Ca-P-Sr specimens exhibited a significant enhancement in surface roughness, hydrophilicity, cell proliferation, cell adhesion. More new bone was found around the Ca-P-Sr coated alloy than Ca-P coated alloy and Ti35Nb2Ta3Zr alloy. In conclusion, the MAO treatment improved in vitro and in vivo performance of Ti35Nb2Ta3Zr alloy. The Ca-P-Sr coating may be a promising modified surface formed by MAO for the novel β-titanium alloy Ti35Nb2Ta3Zr.

Effects of Curing Condition on the Surface Characteristics of Two-pack Polyurethane Coatings Containing Low Surface Energy Additive

To investigate the effects of curing condition on the surface characteristics of polyurethane coatings, the prepared coatings had undergone different curing conditions in which the rate of solvents evaporation differed. Differential scanning calorimeter, Fourier transform infrared spectroscope, atomic force microscope, and contact angle measurement system were used to characterize the coating solution as well as the cured coatings. The results showed that the curing condition substantially influenced the samples’ surface morphology and can be used as a parameter for precise engineering of surface pattern. The highest contact angle of 103° was obtained for the ambient cured sample.

조형가공기술을 이용한 인공지지체의 수산화나트륨 개질 효과

조직공학에서의 인공지지체는 세포의 부착과 증식 및 분화가 잘 되어야 하고, 우수한 생체친화성 및 생분해성을 지녀야 한다. 다양한 인공지지체 제작 방법이 시도되어지고 있으며, 최근들어 3D 프린팅 기술을 이용한 방식이 활발하게 연구되어지고 있다. 폴리카프로락톤(polycaprolactone, PCL)은 낮은 녹는점을 가지고 있어 3D 프린팅하기에 우수한 생체적합 고분자 합성재료이다. 본 연구에서는 3D 프린팅 기술을 이용하여 3차원 PCL 인공지지체를 제작하였고, 지지체의 표면개질을 위해 수산화나트륨(NaOH)을 이용하였다. 표면개질된 인공지지체의 표면특성을 SEM으로 확인한 결과, 수산화나트륨을 처리한 PCL 인공지지체가 처리하지 않은 PCL 인공지지체에 비해 거칠기가 증가함을 보였으며, 접촉각 측정을 통해 친수성이 증가함을 확인하였다. In vitro 실험결과, 수산화나트륨을 처리한 PCL 인공지지체가 처리하지 않은 PCL 인공지지체에 비해 세포의 증식과 분화가 증가함을 보였고, 세포의 부착 모습은 균일하고 밀집된 형태로 부착됨을 확인하였다. 따라서 조형가공기술을 이용하여 수산화나트륨을 처리한 표면개질된 PCL 인공지지체를 제작하고 분석함으로써, 세포적합성을 통해 체내 인공지지체 개발 적용 가능성을 제시하였다. Scaffolds of tissue engineering should be biocompatible and biodegradable for cell attachment, proliferation and differentiation. In the various scaffold fabrication, 3D printing technique can make the three dimensional scaffold with interconnected pores for cell ingrowth. Polycaprolactone (PCL) is biodegradable polyester with a low melting temperature and has been approved by the Food and Drug Administration (FDA). In this study, PCL scaffold was fabricated by 3D bioprinting system and surface modification of PCL scaffold was controlled by NaOH treatment. Morphological change and wetability of NaOH-treated scaffold were observed by SEM and contact angle measurement system. The remnant of PCL treated with NaOH was measured by ATR-FTIR. In vitro study of scaffolds was evaluated with WST-1 and ALP activity assay. NaOH treatment of PCL scaffolds increased surface roughness, hydrophilicity, cell proliferation and osteogenic differentiation. These results indicate that NaOH-treated PCL scaffold made by 3D bioprinting has tissue engineered potential for the development of biocompatible material.

Critical Surface Tension of Cholesteryl Ester Liquid Crystal

Cholesteryl ester liquid crystal was found to be non-toxic and it was recently applied as a cell traction force sensor. The reason for the affinity of the cells to this liquid crystal is unclear and required further investigation. This paper focused on determining the surface energy of the liquid crystals. A custom built contact angle measurement system and Fox-Zisman theory was applied to determine the critical surface tension of the cholesteryl ester liquid crystal. Eight different polar probe liquids were selected to determine the contact angle of the glass slides coated with cholesteryl ester liquid crystals. We found that the critical surface tension of the liquid crystal at 37.5 mN/m characterized the surface of the liquid crystal to be moderately hydrophobic. However, as reported in our previous work that the interaction of the liquid crystal and the cell culture media could re-orientate the amphiphilic molecules of the liquid crystals leading to the formation of lyotropic layers on the bulk cholesteric phase, therefore, making the surface to be hydrophilic. This then supported the formation of the hydrophilic layers that favors cell adhesion.

Optimization and characterization of biomolecule immobilization on silicon substrates using (3-aminopropyl)triethoxysilane (APTES) and glutaraldehyde linker

In the present work, we developed and optimized a technique to produce a thin, stable silane layer on silicon substrate in a controlled environment using (3-aminopropyl)triethoxysilane (APTES). The effect of APTES concentration and silanization time on the formation of silane layer is studied using spectroscopic ellipsometry and Fourier transform infrared spectroscopy (FTIR). Biomolecules of interest are immobilized on optimized silane layer formed silicon substrates using glutaraldehyde linker. Surface analytical techniques such as ellipsometry, FTIR, contact angle measurement system, and atomic force microscopy are employed to characterize the bio-chemically modified silicon surfaces at each step of the biomolecule immobilization process. It is observed that a uniform, homogenous and highly dense layer of biomolecules are immobilized with optimized silane layer on the silicon substrate. The developed immobilization method is successfully implemented on different silicon substrates (flat and pillar). Also, different types of biomolecules such as anti-human IgG (rabbit monoclonal to human IgG), Listeria monocytogenes, myoglobin and dengue capture antibodies were successfully immobilized. Further, standard sandwich immunoassay (antibody–antigen–antibody) is employed on respective capture antibody coated silicon substrates. Fluorescence microscopy is used to detect the respective FITC tagged detection antibodies bound to the surface after immunoassay.

Direct-write assembly of 3D scaffolds using colloidal calcium phosphates inks

Additive manufacture techniques using concentrated colloidal inks are a promising approach for creating three-dimensional (3D) calcium phosphates scaffolds for bone repair and regeneration. Among those, the direct-write assembly allows building scaffolds with precise size and geometry. In the present work, commercial β-TCP and HA were used to produce two types of colloidal ink. According to the ink composition used to build the scaffolds, two different groups were obtained. Group I: scaffolds produced with β-TCP-based ink; and Group II: scaffolds produced with biphasic CaP-based ink (BCP). The 3D scaffolds were assembled in a cylindrical shape (Φ = 8mm x H= 16 mm) with interconnected pore channels of approximately 500μm by robotic deposition of 64 layers using a robocasting machine. The mechanical compression property of the scaffolds was determined using universal testing machine. To assure the controlled geometry of the scaffolds, digital images were obtained by reconstructing each individual scan obtained with a micro-computed tomography. An optical contact angle measurement system was used to evaluate the wettability of the materials. After analyzing the results it was concluded that: the robocasting system is suitable for building 3D periodic calcium phosphates scaffolds; the direct-write assembly didn't change the hydrophilic characteristic of CaPs; and presented mean compressive strength around 11 MPa (β-TCP group) and 15 MPa (BCP group), which is compatible with trabecular bone.

Formation and characterisation of nanoporous TiO 2 layers on microroughened titanium surfaces by electrochemical anodisation

Nanoporous titanium dioxide (TiO2) layers were successfully formed by an electrochemical anodisation method on microroughened titanium (Ti) surfaces in fluoride containing aqueous electrolyte. Microroughened Ti surfaces were produced by sandblasting with Al2O3 particles of 50 μm in diameter and acid-etching in a blend of HCl/H2SO4 solution. The surface morphology, topography and chemical composition of the specimens were analysed by scanning electron microscopy, atomic force microscopy and X-ray photoelectron spectroscopy. The surface roughness and the wettability of treated Ti surfaces were measured using profilometry and a contact angle measurement system, respectively. With anodising of sandblasted-/acid etched surfaces, micrometre- and nanometre-scale textures on titanium specimens were created. Results showed that these developed nanoporous-microroughened surfaces exhibited lower contact angle values than the other treated Ti surfaces. The sandblasted/acid-etched/anodised Ti specimen had a surface morphology with distinctively formed hills and valleys and higher surface roughness than the other anodised specimens. This study indicated that nanoporous TiO2 structures fabricated on microroughened Ti can be an effective way to modify the titanium surfaces for the future development of implant applications.

Nanostructured hydrophobic DC sputtered inorganic oxide coating for outdoor glass insulators

We report the structural, optical and electrical properties of nanostructured hydrophobic inorganic hafnium oxide coating for outdoor glass insulator using DC sputtering technique to combat contamination problem. The properties were studied as a function of DC power. The characterization of the films was done using X-ray diffraction, EDS, surface profilometer, AFM, impedance analyser and water contact angle measurement system. The DC power was varied from 30 to 60W and found to have a great impact on the properties of hafnium oxide. All the deposited samples were polycrystalline with nanostructured hydrophobic surfaces. The intensity of crystallinity of the film was found to be dependent on sputtering power and hydrophobicity was correlated to the nanoscale roughness of the films. The optical property reveals 80% average transmission for all the samples. The refractive index was found in the range of 1.85–1.92, near to the bulk value. The band gap calculated from transmission data was >5.3eV for all deposited samples ensuring dielectric nature of the films. Surface energy calculated by two methods was found minimum for the film deposited at 50W sputtering power. The resistivity was also high enough (∼104Ωcm) to hinder the flow of leakage current through the film. The dielectric constant (ɛ) was found to be thickness dependent and also high enough (ɛmax=23.12) to bear the large electric field of outdoor insulators.