Range Of Water Contact Angles Research Articles

Fabrication of functional surfaces using layer height method in material extrusion type 3D printing

Various layer stacking methods have been employed in material extrusion type three-dimensional (3D) printing to utilize their potential for addressing the inherent technological limitation of reduced surface quality due to layer stacking. The process involved fabricating a material extrusion type 3D printed mold using diverse layer height-changing methods and subsequently replicating the surface pattern with the polymer. This approach is called the layer height method (LHM) and comprises three distinct variations. The first method involves altering the height of the individual layers to generate diverse surface morphologies and, consequently, varying the range of water contact angles. The second method focuses on rapid layer height changes to facilitate liquid deposition within regions with low contact angles. Finally, a layer height gradient was systematically established within the mold, resulting in a wettability gradient surface capable of controlling the movement of water droplets across the surface. The performance of these functional surfaces was successfully validated using various experimental methods. This study introduces a manufacturing technique based on changing layer heights within the framework of material extrusion-type 3D printing technology. A wide range of intricate and diverse functional surfaces can be produced by extending the manufacturing method proposed in this study to 3D printing technologies beyond the scope of material extrusion type 3D printing.

Achieving controlled topography and wettability through laser surface texturing of Ti6Al4V for bioengineering applications

The global rise of dental and orthopedic implant treatments in the twenty-first-century appeals to researchers for further investigations. The situation is worsening as the rate of failure and revision treatments are considerable. Inadequate osseointegration and infections are the significant causes of the problem. To address the issue laser surface texturing is proficient to modulate surface topography, morphology, wettability, and chemical characteristics. To date, the implant surface features are not configured to receive an optimal response for early bone healing through cell adhesion and proliferation. Experimental design to investigate optimal responses of Ti6Al4V surface by texturing it with nanosecond Nd: YAG 1064 nm laser is carried out. The evolved research surface methodology model resulted in an efficient parametric relationship with 98.5%, 98.87%, and 96.99% R2 values for ‘kerf width’, ‘Rz’, and ‘kerf width to Rz’ ANOVA analysis respectively. The ANN approach shows more accuracy than the RSM approach for the prediction of ‘kerf width’, ‘Rz’, and ‘kerf width to Rz’. The experiment was performed to attain control in the range of water contact angle 40° to 119° as hydrophilic (ϴ ≤ 90) nature is prominently favorable for cell adhesion and proliferation. The Lower ‘kerf width to Rz ratio’ and higher Rz inclined towards hydrophobicity. An increment in carbon content also assists in rising contact angle. LST improves the Ti oxide layer which is considered a more corrosion-resistive and biocompatible layer. This study will certainly help to develop improved stability and life of dental and orthopedic implant surfaces.

Wetting properties of graphene and multilayer graphene deposited on copper: The influence of copper topography

Graphene-based coatings are promising in optoelectronic, membrane, sensor-related and cooling technologies due to their outstanding properties. However, during the use of these applications, coatings are contacting with water. Therefore, changes in the wetting properties and water evaporation rate on graphene-coated samples are of particular interest to ensure the correct operation of these devices. The purpose of this work is to study the influence of texture, crystallographic orientation and annealing on wetting and water droplet evaporation on copper with graphene or multilayer graphene coating. The texture and grain structure of graphene coated copper samples were analyzed using Raman scattering and scanning electron microscopy. Modifying the surface texture by pressing and varying the annealing time makes it possible to achieve the orientation of grains (111), as well as the simultaneous presence of different crystalline orientations. Wetting properties were changed in a fairly wide range of water contact angles (72°–110°) by changing the annealing time, texturing the surface and forming the graphene-based coating and MLG coating. The droplet evaporation modes, evaporation time and evaporation rates varied on different surfaces. A texture surface accelerated the droplet evaporation; a smooth copper surface maximized the evaporation time while surface texturing from multilayer graphene coating minimized it.

Hydrophobic MXene/Hydroxyethyl Cellulose/Silicone Resin Composites with Electromagnetic Interference Shielding

AbstractExploring a method to fabricate robust and stable 3D conductive networks in polymers matrix is still the challenge in the research and development of electromagnetic interference (EMI) shielding materials. Here, a feasible approach is provided to produce high‐performance, silicone‐doped MXene EMI shielding composites. The trace amount of hydroxyethyl cellulose is deliberately applied as gels to construct the MXene aerogels with a stable and highly conductive network by the freeze‐drying method. For more desirable mechanical and waterproof properties, the silicone resin is introduced into the MXene aerogels on purpose. The best silicone‐doped MXene EMI shielding composites display a superior electrical conductivity of 3166.4 S m−1, and EMI shield effectiveness of 74.5 dB at the X‐band (8.2–12.4 GHz). It is worth noting that the introduction of silicone resins sharply improves the hydrophobicity of EMI shielding materials to a range of water contact angle of about 151.5°–155.0°. This is a promising method to make MXene‐based EMI shielding composites with self‐cleaning function.

Femtosecond laser pulse inducing hydrophilicty and hydrophobicity on polycarbonate surfaces

This study investigated the use of ultrashort femtosecond laser pulses to induce either hydrophilic or hydrophobic surfaces on polycarbonate (PC). It has been observed that controlled modification of wettability could be achieved over a wide range of water contact angle (WCA) from below 5° to above 150°. It has been shown that the pulse energy fluence and total energy deposition onto PC are the important factors in determining the laser-PC interaction, and therefore the different level of wettability on PC surface. XPS-spectra measurement indicates that the modification was caused dominantly by laser induced chemical bond changes. The changes in surface morphology may not noticeably contribute to the surface wettability. The results would be useful in microfluidics chip design and fabrication with controlled surface wetting properties.

Silicone Surface Fundamentals.

Many of the applications of the most familiar silicone polymer, polydimethylsiloxane (PDMS), are a consequence of its hydrophobic nature. The key quantities underlying this behavior are the water contact angle with water droplets, the surface tension of the polymer, and its interfacial tension with water. These quantities are reviewed for PDMS and the fluorsilicone polymethyltrifluoropropylsiloxane (PMTFPS) as well as some other less common, more highly fluorinated, fluorosilicones. As aliphatic fluorocarbons are usually introduced into polymers to lower surface tension, it is unexpected that the surface tension of PMTFPS is higher than PDMS. However, this observation is consistent with Zisman's early extensive studies. It is also somewhat surprising that there are no definitive values accepted for the water contact angle with PDMS and the interfacial tension at the PDMS/water interface. Some reasons for this are explored and relevant limitations considered. The variety of ways in which a PDMS surface can be presented must have a major effect on the range of water contact angles reported.

Tailoring Surface Hydrophobicity of Commercial Polyimide by Laser-Induced Nanocarbon Texturing

Abstract The growth of laser-induced nanocarbons, referred to here as laser-induced nanocarbon (LINC) for short, directly on polymeric surfaces is a promising route toward surface engineering of commercial polymers. This paper aims to demonstrate how this new approach can enable achieving varied surface properties based on tuning the nanostructured morphology of the formed graphitic material on commercial polyimide (Kapton) films. We elucidate the effects of tuning laser processing parameters on the achieved nanoscale morphology and the resulting surface hydrophobicity or hydrophilicity. Our results show that by varying lasing power, rastering speed, laser spot size, and line-to-line gap sizes, a wide range of water contact angles are possible, i.e., from below 20 deg to above 110 deg. Combining water contact angle measurements from an optical tensiometer with LINC surface characterization using optical microscopy, electron microscopy, and Raman spectroscopy enables building the process–structur–property relationship. Our findings reveal that both the value of contact angle and the anisotropic wetting behavior of LINC on polyimide are dependent on their hierarchical surface nanostructure which ranges from isotropic nanoporous morphology to fibrous morphology. Results also show that increasing gap sizes lead to an increase in contact angles and thus an increase in the hydrophobicity of the surface. Hence, our work highlight the potential of this approach for manufacturing flexible devices with tailored surfaces.

Investigation on polycarbonate surface wetting property with femtosecond laser irradiation and ultrasonic treatment

This study investigated the use of ultrashort femtosecond laser pulses to induce either hydrophilic or hydrophobic surfaces on polycarbonate (PC). It has been observed that controlled modification of wettability could be achieved over a wide range of water contact angle (WCA) from below 5° to above 150°. It has been shown that the pulse energy fluence and total energy deposition onto PC are the important factors in determining the laser-PC interaction, and therefore the different level of wettability on PC surface. XPS-spectra measurement indicates that the modification was caused dominantly by laser induced chemical bond changes. The changes in surface morphology may not noticeably contribute to the surface wettability. The stability investigation on the wetting property of laser modified surfaces has shown that ultrasonication in DI water or in ethanol led to decrease in hydrophobicity, and the decrease was more pronounced for super-hydrophobic surfaces. The level of hydrophilicity decreased as well for the laser induced hydrophilic surfaces. However, the change in hydrophobicity by post-treatment was not significant. The results would be useful in microfluidic chip design and fabrication with controlled surface wetting properties.

Facile and versatile solid state surface modification of silk fibroin membranes using click chemistry.

Reported is a fast and versatile protocol to surface modify pre-cast silk membranes targeting tyrosine residues. Enriched alkyne silk membranes were prepared using this method and azides possessing a range of functional groups were tethered to the membrane surface using click chemistry to give a range of water contact angles from 85 ± 3° to 34 ± 6°.

Sphingosine-1-Phosphate Immobilized on Nanotopographical Scaffolds Improve Myogenic Differentiation.

The skeletal muscle consists of highly aligned dense cables of collagen fibers with nanometer feature size to support muscle fibers. The skeletal myocyte can be greatly affected to differentiate by their surrounding topographical structure. To improve myogenic differentiation, we fabricated cell culture platform that sphingosine-1-phosphate (S1P) which regulated myocyte behavior is immobilized on a biomimetic nanopatterned polyurethaneacrylate (PUA) substrate using 3,4-dihydroxyphenylalanine (L-DOPA) for providing topographical and biological cues synergistically. In the present study, we hypothesized that cultured C2C12 cells can be induced to synergistically promote myogenic differenntiation on nanopatterned PUA-L-DOPA-S1P. We confirmed that nanopatterned PUA-L-DOPA-S1P has high hydrophilicity with a suitable range of water contact angle and small intensity of phosphate peak (P2p) by analyses of water contact analyzer and X-ray photoelectron spectroscopy. In addition, C2C12 cells culured on nanopatterned PUA-L-DOPA-S1P has well-oriented and organized myodubes formed with greater expression of myogenic regulatory factors such as MyoD and MyoG comapred to flat PUA groups. This functional platform which is not only provided topographical and biological cues has a suitable potential function to apply muscle cell niche as similar structure of muscle fiber but also utilized cell behavior within tissue engineered scaffolds and cellular microenvironment.

Controlled Wetting Properties through Heterogeneous Surfaces Containing Two-level Nanofeatures.

Addressing the direct control of surface wettability has been a significant challenge for a variety of applications from self-cleaning surfaces to phase-change applications. Surface wettability has been traditionally modulated by installing surface nanostructures or changing their chemistry. Among numerous nanofabrication efforts, the chemical oxidation method is considered a promising approach because it allows cost-effective, quick, and direct control of the morphologies and chemical compositions of the grown nanofeatures. Despite the wide applicability of the surface oxidation method, the precise control of wetting behaviors through the growth of nanostructures has yet to be addressed. Here, we investigate the wetting characteristics of heterogeneous surfaces that contain two-level features (i.e., nanograsses and nanoflowers) with different petal shapes and structural chemistry. The difference in growth rates between nanograsses and nanoflowers creates a time-evolving morphology that can be classified by grass-dominated or flower-dominated regimes, which induces a wide range of water contact angles from 120 to 20°. The following study systematically quantifies the structural details and chemistry of nanostructures associated with their wetting characteristics. This investigation of heterogeneous surfaces will pave the way for selective growth of copper nanostructures and thus a direct control of surface wetting properties for use in future copper-based thermal applications.

Photo-initiated chemical vapor deposition of thin films using syngas for the functionalization of surfaces at room temperature and near-atmospheric pressure

Hydrophilic and hydrophobic thin films have been deposited onto flat metallic substrates through photo-initiated chemical vapor deposition (PICVD), using syngas as a precursor, and affordable UVC germicidal lamps as a source of light. This study is the first experimental investigation of what has been previously concluded to be the potential solution to the current widespread nanoparticle functionalization problem. This study addresses the current limiting factor, namely the cost issue, by using simple gas precursors, using an affordable initiation source and operating under normal conditions. This approach differs from the current approaches which use expensive solvents as precursors, energy consuming-sources of initiation (e.g. high temperature, plasma and VUV) and operate under high vacuum and/or high temperatures. While the current paradigm is to target the peak absorption of a molecule, the present study indicates that long chain polymerized products can be formed from off-peak wavelengths. It has been found that photo-initiated deposition occurs and that a wide range of water contact angles, from 5° to 118°, can be obtained by manipulating the experimental conditions. A multilinear empirical model has been derived, and it predicts fairly well the contact angles obtained as a function of the different experimental parameters.

Tuning the hydrophobicity of plasma polymer coated silica particles

The modification of particle hydrophobicity has been conventionally carried out using wet chemistry methods. This investigation has however applied plasma polymerisation as a novel approach to produce silica particles with tailored hydrophobicity. Deposition of plasma polymerised 1,7-octadiene (ppOD) was carried out using a radio frequency inductively coupled reactor fitted with a rotating chamber. Plasma polymerisation parameters were varied to study the hydrophobicity of hydrocarbon functionalised particles. The surface chemistry of the ppOD coated particles was analysed via X-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectrometry. Deposition of ppOD coatings under low specific energy plasma conditions resulted in both chemically and hydrophobically heterogeneous ensemble of particles. Whereas optimised plasma conditions resulted in homogeneous ppOD coatings. Development of hydrophobicity in ppOD coated particles was confirmed by Washburn capillary rise measurements, film flotation tests and environmental scanning electron microscopy observations. Silica particles with a range of water contact angles from 36° to more than 90° were obtained by controlled deposition of ppOD films. Plasma polymerisation using a rotating reactor has shown to be an efficient approach in the surface modification of silica particles to obtain surfaces with controlled hydrophobicity, which are of direct interest in a diverse range of practical applications as well as fundamental studies.

Perpendicularly Oriented Cylinder Nanostructure of Liquid Crystalline Block Copolymer Film on Si Substrate with Various Surface Wettability

Abstract Hexagonally arranged PEO cylinders in the PEOm-b-PMA(Az)n thin film were perpendicularly oriented on Si wafer substrates with a wide range of water contact angle (<5° to 85°) by controlled modification with octadecyltrichlorosilane (OTS). Additionally, the film was stiffly adhered on the modified substrate due to an anchoring effect of partly covered monolayer of OTS.

Evaluation of Cell Behaviour on Atmospheric Plasma Deposited Siloxane and Fluorosiloxane Coatings

For developing functional biomaterials, an understanding of the biological response at material surfaces is of key importance. In particular, surface chemistry, roughness and cell type influence this response. Many previous reports in the literature have involved the study of single cell types and their adhesion to surfaces with a limited range of water contact angles. The objective of this study was to investigate the adhesion of five cell lines on surfaces with contact angles in the range of 20° to 115°. This range of water contact angles was obtained using siloxane and fluorosiloxane coatings deposited using atmospheric plasma deposition. These nm thick coatings were deposited by nebulizing liquid precursors consisting of poly(dimethylsiloxane) (PDMS) and a mixture of perfluorodecyl acrylate/tetraethylorthosilicate (PPFDA/TEOS) into the atmospheric plasmas. Cell adhesion studies were carried out with the following cell types: Osteoblast, Human Embryonic Kidney (HEK), Chinese hamster ovary (CHO), Hepatocytes (HepZ) and THP1 leukemic cells. The study demonstrated that cell adhesion was significantly influenced by the type of cell line, water contact angle and coating chemistry. For example, the sensitivity of cell lines to changes in contact angle was found to decrease in the following order: Osteoblasts > Hepatocytes > CHO. The HEK and THP-1 inflammatory cells in contrast were not found to be sensitive to changes in water contact angle.

Precise control of wettability from LCST tunable surface

In this study, we demonstrated precise control of wettability from a thermally-responsive surface and investigated the effects of chemical composition and surface roughness. By altering feeding manners of initiators during surface grafting process of poly(N-isopropylacrylamide-co-N-isopropylmethylacrylamide) [poly(NIPAAm-co-NIPMAM)], two thermally-responsive wettability transitions were achieved and could be precisely controlled. Only using initiators grafted on surface for grafting copolymerization, surface wettability exhibited a gradual even linear transition between hydrophilic and hydrophobic within 25–45 °C, whereas for initiators both grafted on surface and dissolved in solution, surface wettability sharply switched within 2 °C and their lower critical solution temperature (LCST) can be tuned with every step of about 3 °C in the range 32–45 °C by adjusting the ratios of comonomers. The underlying mechanism was proposed to clarify the relations between different thermally-responsive behaviors of surface wettability and surface chemical composition induced by different feeding manners of initiators. Furthermore, the introduction of surface roughness could not only enlarge the changing range of water contact angle (CA) by 60–100°, but also affect the thermally-responsive behaviors of surface wettability from the gradual changing to sharp switching in partial region of temperature.

Attachment and detachment of bacteria on surfaces with tunable and switchable wettability

Controlling accumulations of unwanted biofilms requires an understanding of the mechanisms that organisms use to interact with submerged substrata. While the substratum properties influencing biofilm formation are well studied, those that may lead to cellular or biofilm detachment are not. Surface-grafted stimuli-responsive polymers, such as poly (N-isopropylacrylamide) (PNIPAAm) release attached cells upon induction of environmentally-triggered phase changes. Altering the physicochemical characteristics of such polymeric systems for systematically studying release, however, can alter the phase transition. The physico-chemical changes of thin films of PNIPAAm grafted from initiator-modified self-assembled monolayers (SAMs) of ω-substituted alkanethiolates on gold can be altered by changing the composition of the underlying SAM, without affecting the overlying polymer. This work demonstrates that the ability to tune such changes in substratum physico-chemistry allows systematic study of attachment and release of bacteria over a large range of water contact angles. Such surfaces show great promise for studying a variety of interactions at the biointerface. Understanding of the source of this tunability will require further studies into the heterogeneity of such films and further investigation of interactions beyond those of water wettability.

Multifunctional Silane Polymers for Persistent Surface Derivatization and Their Antimicrobial Properties

We demonstrate a versatile methodology combining both covalent surface anchoring and polymer cross-linking that is capable of forming long-lasting coatings on reactive and nonreactive surfaces. Polymers containing reactive methoxysilane groups form strong Si-O-Si links to oxide surfaces, thereby anchoring the polymer chains at multiple points. The interchain cross-linking of the methoxysilane groups provides additional durability to the coating and makes the coatings highly resistant to solvents. By tailoring the chemical structure of the polymer, we were able to control the surface energy (wetting) of a variety of surfaces over a wide range of water contact angles of 30-140 degrees . In addition, we synthesized covalently linked layer-by-layer polymeric assemblies from these novel methoxysilane polymers. Finally, antibacterial agents, such as silver bromide nanoparticles and triiodide ions, were introduced into these functional polymers to generate long-lasting and renewable antiseptic coatings on glass, metals, and textiles.

Surface energy of the plasma treated Si incorporated diamond-like carbon films

Surface energy and surface chemical bonds of the plasma treated Si incorporated diamond-like carbon films (Si-DLC) were investigated. The Si-DLC films were prepared by r.f. plasma assisted chemical vapor deposition using benzene and diluted silane (SiH 4/H 2 = 10:90) as the precursor gases. The Si-DLC films were subjected to plasma treatment using various gases like N 2, O 2, H 2 and CF 4. The plasma treated Si-DLC films showed a wide range of water contact angles from 13.4° to 92.1°. The surface energies of the plasma treated Si-DLC films revealed a high polar component for O 2 plasma treated Si-DLC films and a low polar component for CF 4 plasma treated Si-DLC films. The CF 4 plasma treated Si-DLC films indicated the minimum surface energy. X-ray photoelectron spectroscopy (XPS) revealed that the polarizability of the bonds present on the surface explains the hydrophilicity and hydrophobicity of the plasma treated Si-DLC films. We also suggest that the O 2 plasma treated surface can provide an excellent hemocompatible surface from the estimated interfacial energy between the plasma treated Si-DLC surface and human blood.

Effects of surface wettability and contact time on protein adhesion to biomaterial surfaces

Atomic force microscopy (AFM) was used to directly measure the adhesion forces between three test proteins and low density polyethylene (LDPE) surfaces treated by glow discharge plasma to yield various levels of water wettability. The adhesion of proteins to the LDPE substrates showed a step dependence on the wettability of surfaces as measured by the water contact angle ( θ). For LDPE surfaces with θ>∼60–65°, stronger adhesion forces were observed for bovine serum albumin, fibrinogen and human FXII than for the surfaces with θ<60°. Smaller adhesion forces were observed for FXII than for the other two proteins on all surfaces although trends were identical. Increasing the contact time from 0 to 50 s for each protein–surface combination increased the adhesion force regardless of surface wettability. Time varying adhesion data was fit to an exponential model and free energies of protein unfolding were calculated. This data, viewed in light of previously published studies, suggests a 2-step model of protein denaturation, an early stage on the order of seconds to minutes where the outer surface of the protein interacts with the substrate and a second stage involving movement of hydrophobic amino acids from the protein core to the protein/surface interface. Impact statement: The work described in this manuscript shows a stark transition between protein adherent and protein non-adherent materials in the range of water contact angles 60–65°, consistent with known changes in protein adsorption and activity. Time-dependent changes in adhesion force were used to calculate unfolding energies relating to protein–surface interactions. This analysis provides justification for a 2-step model of protein denaturation on surfaces.