Surface Modification Applications Research Articles

Versatile Polydopamine Platforms: Synthesis and Promising Applications for Surface Modification and Advanced Nanomedicine.

As a mussel-inspired material, polydopamine (PDA), possesses many properties, such as a simple preparation process, good biocompatibility, strong adhesive property, easy functionalization, outstanding photothermal conversion efficiency, and strong quenching effect. PDA has attracted increasingly considerable attention because it provides a simple and versatile approach to functionalize material surfaces for obtaining a variety of multifunctional nanomaterials. In this review, recent significant research developments of PDA including its synthesis and polymerization mechanism, physicochemical properties, different nano/microstructures, and diverse applications are summarized and discussed. For the sections of its applications in surface modification and biomedicine, we mainly highlight the achievements in the past few years (2016-2019). The remaining challenges and future perspectives of PDA-based nanoplatforms are discussed rationally at the end. This timely and overall review should be desirable for a wide range of scientists and facilitate further development of surface coating methods and the production of PDA-based materials.

Polymer Brushes Immersed in Two-Component Solvents with Pure Volume Exclusion: Effect of Solvent Molecular Shape

Polymer brushes have wide application in surface modification. We study dense, short polymer brushes immersed in a mixing solvent under athermal conditions using the classical density functional theory. The brush polymer is short so that the equilibrium behavior of the brush deviates far from the scaling laws for infinite brush chains. The excluded volume interaction is the only interaction in the system. We compare the excluded volume effect of solvent molecules of different shapes. Two types of mixing solvents are considered: solvent composed of linear oligomers and monomers, or that of spherical particles and monomers. The effects of grafting density, solvent molecular size, and solvent number density on the brush height, the density profiles, the relative excess adsorption, and the brush–solvent interface width are systematically analyzed. In the adsorption aspect, the spherical particles have stronger ability than the linear oligomers do to penetrate through the brush layer and gather at the substrate. In the screening aspect, the oligomers are more capable of screening the excluded volume interaction between the brush chains than the spherical particles. The brush–solvent interface width decreases monotonically with increasing oligomer length, but it has a minimum with the increasing spherical particle size. Our research differentiates the attractive-interaction-induced phenomenon and the volume-exclusion-induced phenomenon in dense brush systems and exhibits the difference in the antifouling properties of the brushes contacting solvent molecules of different shapes.

Inducing locally structured ion energy distributions in intermediate-pressure plasmas

Ion energy distribution functions (IEDFs) incident upon material surfaces in radio frequency (rf) capacitively coupled plasmas are coupled to spatial and temporal sheath dynamics. Tailoring the ion energy distribution function within intermediate-pressure plasmas (≈133 Pa, 1 Torr), which find application in surface modification and aerospace industries, is challenging due to the collisional conditions. In this work, experimentally benchmarked 2D fluid/Monte-Carlo simulations are employed to demonstrate the production of structured IEDFs in a collisional (200 Pa 1.5 Torr argon) rf hollow cathode discharge. The formation of structures within the IEDFs is explained by an increase in the Ar+ ion-neutral mean-free-path and a simultaneous decrease in the phase-averaged sheath extension as the rf voltage frequency increases over 13.56–108.48 MHz for a constant rf voltage amplitude (increasing plasma power) and gas flow rate. Two distinct transitions in the shape of the IEDF are observed at 450 V, corresponding to the formation of “mid-energy” (60–180 eV) structures between 40.68 and 54.24 MHz and additional “high energy” (≳180 eV) structures between 81.36 and 94.92 MHz, with the structures within each region displaying a distinct sensitivity to the applied voltage amplitude. Transitions between these energy ranges occurred at lower applied voltages for increased applied voltage frequencies, providing increased control of the mean and modal ion energy over a wider voltage range. The capabitlity to extend the range of access to an operational regime, where the structured IEDFs are observed, is desirable for applications that require control of the ion-bombardment energy under collisional plasma conditions.

From macro to micro, evolution of surface structures on cutting tools: a review

In modern tool industry, the design and manufacture of cutting tool surface have been highlighted to fulfill the ever-increasing demands of advanced manufacturing, e.g., lean production, intelligent manufacturing and Industry 4.0. Chip-breaker is a triumph of applying the specific macro structure on rake face, not only contributing to chip controlling, but also being capable to reduce cutting force and tool temperature. In recent decade, surface texturing has been emerged on tool surface, indicating that research focus of surface structures on tools is evolving from macroscale to microscale. The present study reviews functions, optimization and manufacture approaches of different scale structures on cutting tools, aiming at providing a global view of related technologies and revealing the possible developing tendency in this field. This paper could greatly facilitate future research and industrial application of tool surface modification, especially for the integrated application in multi-scale.

UV-Responsive Multilayers with Multiple Functions for Biofilm Destruction and Tissue Regeneration.

The increasing demands of surgical implantation highlight the significance of anti-infection of medical devices, especially antibiofilm contamination on the surface of implants. The biofilms developed by colonized microbes will largely hinder the adhesion of host cells, leading to failure in long-term applications. In this work, UV-responsive multilayers were fabricated by stepwise assembly of poly(pyrenemethyl acrylate- co-acrylic acid) (P(PA- co-AA)) micelles and chitosan on different types of substrates. Under UV irradiation, the cleavage of pyrene ester bonds in the P(PA- co-AA) molecules resulted in the increase of roughness and hydrophilicity of the multilayers. During this process, reactive oxygen species were generated in situ within 10 s, which destroyed the biofilms of Staphylococcus aureus, leading to the degradation of the bacterial matrix. The antibacterial rate was above 99.999%. The UV-irradiated multilayers allowed the attachment and proliferation of fibroblasts, endothelial cells, and smooth muscle cells, benefiting tissue integration of the implants. When poly(dimethylsiloxane) slices with the multilayers were implanted in vivo and irradiated by UV, the density of bacteria and the inflammatory level (judging from the number of neutrophils) decreased significantly. Moreover, formation of neo blood vessels surrounding the implants was observed after implantation for 7 days. These results reveal that the photoresponsive multilayers endow the implants with multifunctions of simultaneous antibiofilm and tissue integration, shedding light for applications in surface modification of implants in particular for long-term use.

Design, Synthesis, and Application of a Difunctional Y-Shaped Surface-Tethered Photoinitiator.

Mixed homopolymer brushes have unique interfacial properties that can be exploited for both fundamental studies and applications in technology. Herein, the synthesis of a new catechol-based biomimetic Y-shaped binary photoinitiator (Y-photoinitiator) and its applications for surface modification with polymer brushes through both "grafting to" and "grafting from" strategies are reported. The "leg" of the Y consists of a catechol group as surface anchoring moiety. The arms are photoinitiator moieties that can be "addressed" independent of each other by radiation of different wavelengths. Using ultraviolet and visible light successively, each arm of the Y-photoinitiator was activated, thereby allowing the synthesis of Y-shaped block copolymer brushes with dissimilar polymer chains. The suitability of the Y-photoinitiator for surface modification was first investigated using N-vinylpyrrolidone and styrene as the model monomers for successive UV-photoiniferter-mediated polymerization and visible-light-induced polymerization, respectively. Switching of the wetting properties of the Y-shaped block copolymer brush poly( N-vinylpyrrolidone)- block-poly(styrene) (PVP- b-PS)-grafted surfaces by contact with different solvents was also investigated. To further exploit this novel Y-photoinitiator for the preparation of functional interfaces, Y-shaped block copolymer brushes poly(1-(2-methacryloyloxyhexyl)-3-methylimidazolium bromide)- block-poly( N-vinylpyrrolidone- co-glycidyl methacrylate) (PIL(Br)- b-P(NVP- co-GMA)) were also prepared and subsequently functionalized with the cell-adhesive arginine-glycine-aspartic acid (RGD) peptides by reaction with the glycidyl groups (PILPNG-RGD). The PILPNG-RGD grafted surfaces showed excellent cell-adhesive, bacteriostatic, and bactericidal properties. Thus, it can be concluded that further exploitation of this novel Y-photoinitiator for graft polymerization should allow the preparation of a wide range of functional interfaces with tailored properties.

Enhanced 1T'-Phase Stabilization and Chemical Reactivity in a MoTe2 Monolayer through Contact with a 2D Ca2 N Electride.

Among the widely studied 2D transition metal dichalcogenides (TMDs), MoTe2 has attracted special interest for phase-change applications due to its small 2H-1T' energy difference, yet a large scale phase transition without structural disruption remains a significant challenge. Recently, an interesting long-range phase engineering of MoTe2 has been realized experimentally by Ca2 N electride. However, the interface formed between them has not been well understood, and moreover, it remains elusive how the presence of Ca2 N would affect the basal plane reactivity of MoTe2 . To address this, we performed density functional theory (DFT) calculations to investigate the potential of tuning the phase stability and chemical reactivity of a MoTe2 monolayer via interacting with Ca2 N to form a van der Walls heterostructure. We found that the contact nature at the 2H-MoTe2 /Ca2 N interface is Schottky-barrier-free, allowing for the spontaneous electron transfer from Ca2 N to 2H-MoTe2 to make it strongly n-type doped. Moreover, Ca2 N doping significantly lowers the energy of 1T'-MoTe2 and dynamically triggers the 2H-to-1T' transformation. The Ca2 N-induced phase modulation can also be applied to tune the phase energetics of MoS2 and MoSe2 . Furthermore, using H adsorption as the testing ground, we also find that the H binding on the basal plane of MoTe2 is enhanced after forming heterostructure with Ca2 N, potentially providing basis for surface modification and other related catalytic applications.

Design & experiments on pen-shaped plasma torch for surface modification

The paper presents design and experiments on pen-shaped plasma torch that generates non-thermal plasma for various surface modification applications. Plasma is used for a variety of industrial applications like surface modifications, surface activation, and surface treatment for coating technology. The hydrophilic property of plastic strip and polyethylene is enhanced by surface treatment done by the plasma torch. The device construction is simple and effective. The present available device is still not feasible for practical applications for its limited effective surface treating area. In this context, the new design of the “pen-shaped plasma torch” performs efficiently in treating area due to swirl motion. To validate this experiments are carried out with designed pen-shaped plasma torch at constant pressure investigating the behavior of the generated plasma for various application of surface modification. The result shows that the stable plasma is achieved at a gas flow rate in the range of 16–18 L min−1 along with the electrode gap in the range of 1.0–1.2 mm. After plasma treatment, the writing ability on plastic film, cleaning on steel plunger and etching ability on the copper strip was improved. The setup established provides fundamental information on plasma generation and practical aspect of surface modification characterization.

Application of surface modification using sodium hypochlorite for helping flotation separation of acrylonitrile-butadiene-styrene and polystyrene plastics of WEEE

Acrylonitrile-butadiene-styrene (ABS) and polystyrene (PS), as important fractions of Waste from Electric and Electronic Equipment (WEEE) plastics, show great significances to the recycling of WEEE. The objective of this study is to develop a simple, practical and efficient surface modification method using sodium hypochlorite (NaClO) for separation of waste ABS and PS plastics by the aid of froth flotation. After surface modification, more hydrophilic groups are introduced on ABS surface than that of PS, enhancing its surface hydrophilicity clearly and reducing its recovery in floated products. Single parameter experiments demonstrate NaClO concentration, treatment temperature, treatment time are key parameters in surface modification. Optimization of conditions for surface modification of ABS was conducted by Response Surface Methodology with a Box-Behnken design, and a predicting model was obtained also. The optimum conditions are NaClO concentration of 0.05 M/L, temperature of 67.50 °C, treatment time 59.50 min and stirring rate of 200 rpm. Under optimum conditions, ABS and PS with different particle sizes can be separated efficiently with recovery of 99.18% and 99.47%, and purity of 99.45% and 99.18% respectively. The application of surface modification using sodium hypochlorite can facilitate efficient flotation separation of waste ABS and PS plastics for the recycling of WEEE.

Orthogonal Molecular Recognition of Chaotropic and Hydrophobic Guests Enables Supramolecular Architectures

AbstractThe hydrophobic and chaotropic effects can be used as orthogonal assembly motifs in water. Cucurbit[7]uril, a water‐soluble macrocyclic host, and a ditopic guest molecule, carrying an organic‐hydrophobic (adamantane) and an inorganic‐chaotropic (dodecahydro‐closo‐dodecaborate dianion) binding site, have been used to construct hybrid supramolecular architectures. The hydrophobic effect drives the adamantane moiety into the host cavity, while the chaotropic effect allows the association of the dodecaborate cluster onto the host exterior surface. This new strategy facilitates potential applications in surface modification, separation, and purification.

Enhanced corrosion and wear resistance of AZ31 magnesium alloy in simulated body fluid via electrodeposition of nanocrystalline zinc

In order to prolong the service life of magnesium-based implants in the human body, nanocrystalline zinc (30 nm) was electrodeposited on AZ31 magnesium alloy, its electrochemical and tribological properties in simulated body fluid (SBF) were investigated. It was demonstrated that electrodeposition of nanocrystalline zinc resulted not only in more than 4 times increase in corrosion resistance, but also in a significant enhancement in corrosive wear resistance of magnesium alloy. Detailed analyses were conducted to clarify the mechanism responsible for performance improvements. This is a biocompatible, economical and simple approach with the promise for large-scale application in surface modification of magnesium alloy implants.

The prospect of layered double hydroxide as bone implants: A study of mechanical properties, cytocompatibility and antibacterial activity

Abstract With the ability to host anions or neutral drugs, layered double hydroxide (LDH) are hot spots in the field of biomaterials. Intensive works so far only have focused on their application in surface modification or injectable medicine. Yet, little literatures report the potential of LDH as bone implants. In the present study, four types of LDH (Mg Al, Mg Fe, Zn Al and Zn Fe) were prepared via a coprecipitation method. Our results showed that the synthetic LDH powders can be pressed into discs in the absence of binder. The discs can maintain their shape after immersed in culture medium for 10 days, not including Mg Al LDH disc. The elastic modulus of all discs was between 9 and 35 GPa, which was close to cortical bone (5–23 GPa). Zn Al LDH and Zn Fe LDH showed higher cytotoxicity than Mg Al LDH and Mg Fe LDH whether in the form of suspension or extract. Furthermore, even up to 10 mg/mL, the extract of Mg Al LDH and Mg Fe LDH showed no cytotoxicity, while cells were totally died in the extract of Zn Al LDH and Zn Fe LDH. Compared with cells, bacterial showed an even lower tolerance concentration to Zn Al LDH and Zn Fe LDH. This study indicates that Mg-containing LDH show better cytotocompatibility, while Zn-containing LDH show better antibacterial property. With proper elastic modulus and controllable biological effect, LDH are promising to be used as bone implants.

High intensity, macroparticle-free, aluminum ion beam formation

We describe a vacuum arc based system for the generation of repetitively pulsed metal ion beams with very high current density, and the results of experimental investigations of the performance of this new system, as well as the results of numerical simulations. Our approach uses a DC vacuum arc as a metal plasma source, and the beam-forming technique is a hybrid method using features of conventional gridded ion extraction together with some plasma immersion attributes. A hemispherical grid is located some distance from the plasma source so as to intercept part of the metal plasma flow and repetitively pulse-biased to the requisite ion beam energy. Ions are accelerated in the high voltage sheath that forms in front of the biased grid and focused into a converging beam that can be of a very high current density. Space charge neutralization is provided by cold plasma that streams through the grid during the bias-off part of the cycle. At the same time, macroparticles in the vacuum arc plasma are blocked from viewing the target by a metal disk positioned centrally on the hemispherical grid. In the work outlined here, we formed 5 keV aluminum ion beams with a current density up to 470 mA/cm2 at a negative bias amplitude of 3 kV and a pulse repetition rate of 105 pulse per second. The experiments and numerical simulations demonstrate the formation of high-intensity macroparticle-free aluminum ion beams for material surface modification and other possible applications.

Hydrodynamically Formed Uniform Thick Coatings on Microspheres.

Forming uniform thick coatings on microspheres remains a significant challenge in various surface modification and drug delivery applications. In this work, a hydrodynamic method is demonstrated for centering microspheres in droplets with sizes ranging from tens to hundreds of micrometers. The core microspheres stay at the center of the droplets due to the hydrodynamic pressure generated in the surrounding liquid shells, despite the significant density difference between the core microsphere and the liquid shell. Therefore, by using polymerizable liquids that can be solidified thermally or by illumination as the shell layer, core-shell particles with gas, liquid, or solid cores can be surrounded with uniform coatings using the present method.

Modulation of the Electrochemical Reactivity of Solubilized Redox Active Polymers via Polyelectrolyte Dynamics.

Redox active polymers (RAPs) are electrochemically versatile materials that find key applications in energy storage, sensing, and surface modification. In spite of the ubiquity of RAP-modified electrodes, a critical knowledge gap exists in the understanding of the electrochemistry of soluble RAPs and their relation to polyelectrolyte dynamics. Here, we explore for the first time the intersection between polyelectrolyte behavior and the electrochemical response that highly soluble and highly substituted RAPs with viologen, ferrocene, and nitrostyrene moieties elicit at electrodes. This comprehensive study of RAP electrolytes over several orders of magnitude in concentration and ionic strength reveals distinct signatures consistent with surface confined, colloidal, and bulk-like electrochemical behavior. These differences emerge across polyelectrolyte packing regimes and are strongly modulated by changes in RAP coil size and electrostatic interactions with the electrode. We found that, unlike monomer motifs, simple changes in the ionic strength caused variations over 1 order of magnitude in the current measured at the electrode. In addition, the thermodynamics of adsorbed RAP films were also affected, giving rise to standard reduction potential shifts leading to redox kinetic effects as a result of the mediating nature of the RAP film in equilibrium with the solution. Full electrochemical characterization via transient and steady-state techniques, including the use of ultramicroelectrodes and the rotating disk electrode, were correlated to dynamic light scattering, ellipsometry, and viscometric analysis. These methods helped elucidate the relationship between electrochemical behavior and RAP coil size, film thickness, and polyelectrolyte packing regime. This study underscores the role of electrostatics in modulating the reactivity of redox polyelectrolytes.

Modification of Polymer Substrates with Extreme Ultraviolet - Potential Application in Cancer Cell Identification

During the last two decades, the development of laboratory scale extreme ultraviolet sources has been intensified due to growing interest in use of extreme ultraviolet sources photons for various applications in science and technology. In this study, we present a potential application of extreme ultraviolet sources surface modification of polymers to be used as substrates for cancer cell identification. The surface modification of polytetrafluoroethylene (PTFE) polymer samples was performed by a lab scale compact laser-plasma extreme ultraviolet sources source based on a double-stream gas-puff target. The gas target was irradiated with a 3 ns/0.8 J Nd:YAG laser pulse at 10 Hz with 50 and 300 pulses. HCV29 non-malignant transitional epithelium and T24 bladder cells adhesion and proliferation studies on pure and extreme ultraviolet sources modified PTFE surfaces were performed. The extreme ultraviolet sources modified surfaces demonstrated regular increase in cancer cell proliferation comparing to pristine sample. Initial results indicate that extreme ultraviolet sources treated substrates can facilitate the identification of cancer cells

A homogeneous focusing system for diode lasers and its applications in metal surface modification

High power diode lasers are applied in many different areas, including surface modification, welding and cutting. It is an important technical trend in laser processing of metals in the future. This paper aims to analyze the impact of the shape and homogeneity of the focal spot of the diode laser on surface modification. A focusing system using the triplet lenses for a direct output diode laser which can be used to eliminate coma aberrations is studied. A rectangular stripe with an aspect ratio from 8:1 to 25:1 is obtained, in which the power is homogeneously distributed along the fast axis, the power is 1117.6 W and the peak power intensity is 1.1587 × 106 W/cm2. This paper also presents a homogeneous focusing system by use of a Fresnel lens, in which the incident beam size is 40 × 40 mm2, the focal length is 380 mm, and the dimension of the obtained focal spot is 2 × 10 mm2. When the divergence angle of the incident light is in the range of 12.5–20 mrad and the pitch is 1 mm, the obtained homogeneity in the focal spot is the optimum (about 95.22%). Experimental results show that the measured focal spot size is 2.04 × 10.39 mm2. This research presents a novel design of homogeneous focusing systems for high power diode lasers.

Recent Advances in Porous Silicon Based Optical Biosensors

Abstract PSi structures have unique physical and optical properties, which are being exploited for a numerous biomedical applications including biosensing, bioimaging, tissue engineering, and drug delivery. Different PSi optical structures can be fabricated to improve the sensitivity of the optical measurements. A very high surface area per volume of PSi can be used for the higher loading of target analytes in a small sensor area, which helps in increasing sensitivity and allows the miniaturization of biosensor. The specificity of PSi biosensor to the target analyte can be inferred by immobilizing the corresponding bioreceptor such as DNA, enzyme, or antibody via different conjugation chemistries. Finally, PSi is biocompatible material that offers additional advantage in comparison to other sensing platforms for in vivo implantable biosensing applications. This paper reviews fabrication, surface modification, biofunctionalization, and optical biosensing applications of PSi structures with special emphasis on in vivo and PSi photonic particles biosensing.

Surface modification and drug delivery applications of MoS2 nanosheets with polymers through the combination of mussel inspired chemistry and SET-LRP

Abstract Mussel inspired chemistry is a promising surface modification tool, which has attracted great research attention for different applications owing to its universality and interest properties. In this work, a rather simple and efficient method for the surface modification of MoS2 nanosheets with copolymers was achieved through the combination of mussel inspired chemistry and single-electron transfer living radical polymerization (SET-LRP) using 2-methacryloyloxyethyl phosphorylcholine (MPC) and itaconic acid (IA) as the monomers. The obtained MoS2-PDA-poly(MPC-IA) nanocomposites were ascertained by a series of characterization techniques, such as nuclear magnetic resonance spectroscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis and X-ray photoelectron spectroscopy. Moreover, the MoS2-PDA-poly(MPC-IA) nanocomposites showed enhanced dispersbility and great biocompatibility. The results implied that the MoS2-PDA-poly(MPC-IA) nanocomposites showed great potential in the field of biomedical science. In this work, the drug loading capability and controlled drug release behavior towards CDDP have been investigated. The drug loading in MoS2-PDA-poly(MPC-IA) composites is as high as 55.26%. All of these above results suggested that the combination of mussel inspired chemistry and SET-LRP is a facile and efficient strategy for fabrication of MoS2 based polymer nanocomposites with great potential application in biomedical fields.

Synthesis and Application of Aurophilic Poly(Cysteine) and Poly(Cysteine)-Containing Copolymers.

The redox capacity, as well as the aurophilicity of the terminal thiol side groups, in poly(Cysteine) lend a unique characteristic to this poly(amino acid) or polypeptide. There are two major application fields for this polymer: (i) biomedical applications in drug delivery and surface modification of biomedical devices and (ii) as coating for electrodes to enhance their electrochemical sensitivity. The intended application determines the synthetic route for p(Cysteine). Polymers to be used in biomedical applications are typically polymerized from the cysteine N-carboxyanhydride by a ring-opening polymerization, where the thiol group needs to be protected during the polymerization. Advances in this methodology have led to conditions under which the polymerization progresses as living polymerization, which allows for a strict control of the molecular architecture, molecular weight and polydispersity and the formation of block copolymers, which eventually could display polyphilic properties. Poly(Cysteine) used as electrode coating is typically polymerized onto the electrode by cyclic voltammetry, which actually produces a continuous, pinhole-free film on the electrode via the formation of covalent bonds between the amino group of Cysteine and the carbon of the electrode. This resulting coating is chemically very different from the well-defined poly(Cysteine) obtained by ring-opening polymerizations. Based on the structure of cysteine a significant degree of cross-linking within the coating deposited by cyclic voltammetry can be assumed. This manuscript provides a detailed discussion of the ring-opening polymerization of cysteine, a brief consideration of the role of glutathione, a key cysteine-containing tripeptide, and examples for the utilization of poly(Cysteine) and poly(Cysteine)-containing copolymers, in both, the biomedical as well as electrochemical realm.