Surface Activation Technique Research Articles

Novel 3D printed bioactive SiC orthopedic screw promotes bone growth associated activities by macrophages, neurons, and osteoblasts.

Ceramic additive manufacturing currently relies on binders or high-energy lasers, each with limitations affecting final product quality and suitability for medical applications. To address these challenges, our laboratory has devised a surface activation technique for ceramic particles that eliminates the necessity for polymer binders or high-energy lasers in ceramic additive manufacturing. We utilized this method to 3D print bioactive SiC orthopedic screws and evaluated their properties. The study's findings reveal that chemical oxidation of SiC activated its surface, enabling 3D printing of orthopedic screws in a binder jet printer. Post-processing impregnation with NaOH and/or NH4OH strengthened the scaffold by promoting silica crystallization or partial conversion of silicon oxide into silicon nitride. The silica surface of the SiC 3D printed orthopedic screws facilitated osteoblast and neuron adhesion and extensive axon synthesis. The silicate ions released from the 3D printed SiC screws favorably modulated macrophage immune responses toward an M1 phenotype as indicated by the inhibition of TNFα secretions and of reactive oxygen species (ROS) expression along with the promotion of IL6R shedding. In contrast, under the same experimental conditions, Ti ions released from Ti6Al4V discs promoted macrophage TNFα secretion and ROS expression. In vivo tests demonstrated direct bone deposition on the SiC scaffold and a strong interfacial bond between the implanted SiC and bone. Immunostaining showed innervation, mineralization, and vascularization of the newly formed bone at the interface with SiC. Taken altogether, the 3D printed SiC orthopedic screws foster a favorable environment for wound healing and bone regeneration. The novel 3D printing method, based on ceramic surface activation represents a significant advancement in ceramic additive manufacturing and is applicable to a wide variety of materials.

Altering the percolation threshold of PA66‐copper hybrid in an electroless copper deposition process by surface activation of the polymer

AbstractIn this study, the impact of three different principles of surface activation techniques for polyamide fibers on the formation of conductive percolation during the subsequent electroless copper deposition process was investigated. The techniques used are (1) polyamide complexation using a solution mixture of calcium chloride, ethanol and water, (2) atmospheric plasma surface treatment and (3) grafting of 2‐hydroxyethylmethacrylate by radical induced polymerization. As a result, the percolation threshold was shifted to lower copper contents. The copper content required to form conductive structures was reduced ranged between 59% and 89%, depending on the activation techniques. Furthermore, the deposition time was reduced by 37%–57%, resulting in a faster build‐up of the percolation on the fabric. Changes in wetting behavior and substrate surface topography were identified to be the main reasons for these observations. While all applied surface activation techniques led to higher copper contents compared to unmodified reference, the atmospheric plasma modification led to the highest copper contents during the deposition process and a more uniform appearance of the metallised layer.Highlights Three different fiber surface activation methods are evaluated. Fiber surface activation increases wetting and polymer‐metal adhesion. Activated polymer surface leads to faster copper deposition and percolation. Atmospheric plasma modification is the most efficient technique.

Plasma treated‐double layer electrospun fiber mats from thermoplastic polyurethane and gelatin for wound healing applications

AbstractConventional wound treatment options provide a barrier against exogenous microbial penetration but cannot simultaneously provide an antibacterial characteristic and promote healing. However, bioactive dressings can accelerate wound healing and have an antibacterial effect in addition to being able to cover and protect lesions. In this study, double‐layer thermoplastic polyurethane (TPU)‐gelatin fibrous dressings that mimic the epidermis and dermis layers of the skin were fabricated via electrospinning technique. As a bioactive agent, Hypericum perforatum oil (HPO) was utilized to impart antibacterial and therapeutic properties to the dressings. Tannic acid was also used in fiber mat formulations as a cross‐linking agent. Oxygen plasma treatment was applied as a surface activation technique to improve adhesion of TPU and gelation layers. The fiber structure of the mats was revealed by a scanning electron microscopy (SEM) study. Fourier transform infrared (FTIR) spectroscopy was used to demonstrate HPO loading onto the mats. The water vapor transmission rate (WVTR) and fluid absorbency of the mats were compared with some commercial dressings. According to these results, it can be suggested that the mats can be used for moderate to high exudative wounds. All dressings, even the control sample showed antibacterial features against both Staphylococcus aureus and Escherichia coli bacteria due to the tannic acid. In vitro wound healing assays were carried out on the plasma‐treated sample and it was observed that the sample did not negatively affect the migration and proliferation abilities of the cells which are necessary for wound healing. Overall results indicated that the plasma‐treated fibrous mat would be a good candidate as a wound dressing material having an antibacterial character.

Sustainable Synthesis of Highly Functionalized Activated Carbon using Plasma Technology.

Surface functionalized activated carbon (SFAC) has been used for several applications, including adsorption, catalysis and energy storage materials. Existing chemical and physical activation methods for surface functionalization are mostly identified as expensive, inefficient, and non-green methods. Plasma, known as the fourth state of matter, has recently been recognized as an attractive and sustainable method for introducing a higher degree of surface functionality to activated carbon. It also improves the bulk chemical structure and the properties of SFAC. The surface functionalization process is governed by discharge gas, discharge source, discharge efficiency and discharge time. The majority of researchers have utilized oxygen plasma as the discharge gas. However, ammonia, carbon dioxide, atmospheric air, specific gases such as chlorine and hydrogen sulfide, and neutral gases such as nitrogen and argon have also been used as the discharge gas. These plasma activations were conducted under different power conditions (W to kW) and varying treatment times (seconds to hours) using different plasma sources such as dielectric barrier discharge (DBD), arc, radio frequency (RF) and microwave (MW) for the surface functionalization. Most of the researchers have experienced both positive and negative co-relationships between principal parameters and surface functional groups (SFGs), surface area, porosity and other surface features such as roughness and hydrophilicity. However, a comprehensive review on the effects of these parameters on the final material properties is lacking. Therefore, this Review focuses on the recent developments in the utilization of plasma as a surface activation technique for activated carbon. Furthermore, an in-depth analysis of the relationship between experimental parameters and the resultant surface features of activated carbon is carried out and discussed. The functionalization mechanisms related to plasma activation have also been illustrated. The aging effect, which negatively impacts surface functionalized activated carbon, is also emphasized. Finally, the recent advances in applications of SFAC, challenges and future perspectives are discussed in detail.

Alkali-activation of cellulose nanofibrils to facilitate surface chemical modification under aqueous conditions

In this study, we developed a surface-activation technique for cellulose nanofibrils (CNFs) using mild-alkali and aqueous conditions. CNFs were initially processed using the aqueous counter collision (ACC) method to produce Janus-type amphiphilic CNFs with both hydrophilic and hydrophobic faces on the surface of a single nanofibril (ACC-CNF). Selective functionalization of the hydroxy groups on the hydrophilic faces creates an opportunity to develop novel nano-building blocks that introduce heterogeneous and tailored surface characteristics into the design of nanomaterials. In this study, alkaline conditions were used to activate the hydroxy groups on the surface of ACC-CNFs as a pre-treatment for the partial crystalline transformation from cellulose I to cellulose II. We found that alkali treatment with sodium hydroxide (NaOH) solutions (concentration range 1–7 wt%) did not fully transform the structure of ACC-CNFs into cellulose II, nor change the morphology of nanofibrils, as seen from their wide-angle X-ray diffraction patterns and atomic force microscopy images. We also found that the hydroxy groups at the surface region of the ACC-CNFs were sufficiently reactive under the moderate alkali and aqueous conditions to undergo subsequent carboxymethylation. Therefore, alkali treatment of ACC-CNFs with a 1–7 wt% NaOH solution rendered the surface of the ACC-CNFs as sufficiently reactive for chemical modification without morphological changes. This simple method for surface activation of CNFs can be useful in the development of future sustainable and novel materials for a variety of applications.

Life cycle analysis of engineering polymer joining methods using adhesive bonding: fatigue performance and environmental implications

Traditional assembly processes such as screw fastening and riveting are increasingly being replaced by new processes such as adhesive bonding. Life cycle performance including fatigue and durability are critical, for which surface activation techniques are often used with the aim of improving both mechanical and life cycle performance. Within this context, the present paper aims to investigate the life cycle performance of adhesive bonding in relation to engineering polymers considering four surface pre-treatments: mechanical, chemical, plasma, and laser activation. The work focuses on two key aspects: (i) mechanical characterization of fatigue performance by assessing the useful life of joints, and (ii) environmental analysis through Life Cycle Assessment (LCA). The outcome of this study provides important insight into the development of laser and plasma technologies as sustainable surface activation methods for polymer joining methods. The substitution of traditional joining methods (i.e., bolting, riveting) with adhesive bonding will allow reductions in overall product weight to be achieved.

A facile hydrophilic modification strategy initiated by flame treatment of silicone coatings for marine antifouling application

Non-toxic poly(dimethylsiloxane) (PDMS) elastomer antifouling coatings are used to protect marine equipment from biofouling; however, the coatings cannot resist all fouling organisms. Hydrophilic modification is an effective way to enhance antifouling performances in PDMS but most modification methods are complex and inconvenient. In this work, flame treatment was used to replace other complex surface activation techniques, such as plasmas. The sulfobetaine silane and polyvinyl alcohol (PVA) modifications were developed for flame treatment. The sulfobetaine silane-modified flame-treated PDMS reduced diatom adhesion by 99.0% compared to untreated PDMS. The PVA modification involves a two-step spray process and is simpler than sulfobetaine silane modification. This strategy coats PVA on flame-treated PDMS through the crosslinking effect of boric acid on PVA, which reduced diatom adhesion by 86.6% in the lab and gave better antifouling performances in field tests compare to bare PDMS.

Adhesion Imrovement with Plasma Activation Between Aluminum Alloys

Aluminum alloys are advantageous light metals in many respects. In the use of these alloys in the ship, aviation and automotive industries, bonding applications rather than welded joints or mechanical connections are preferred. Improving adhesion properties with various surface treatments applied to aluminum alloys is an important issue. Adhesive type, front surface treatments and surface activation techniques control adhesion strength. In this study, the effect of plasma surface treatment technology on adhesion strength was examined in detail. The water drop wetting ability of the alloys were examined, and then adhesion properties were compared with adhesion tests. It has been determined that plasma technology significantly increases the adhesion strength.

Enhanced Protein Immobilization on Polymers-A Plasma Surface Activation Study.

Over the last years, polymers have gained great attention as substrate material, because of the possibility to produce low-cost sensors in a high-throughput manner or for rapid prototyping and the wide variety of polymeric materials available with different features (like transparency, flexibility, stretchability, etc.). For almost all biosensing applications, the interaction between biomolecules (for example, antibodies, proteins or enzymes) and the employed substrate surface is highly important. In order to realize an effective biomolecule immobilization on polymers, different surface activation techniques, including chemical and physical methods, exist. Among them, plasma treatment offers an easy, fast and effective activation of the surfaces by micro/nanotexturing and generating functional groups (including carboxylic acids, amines, esters, aldehydes or hydroxyl groups). Hence, here we present a systematic and comprehensive plasma activation study of various polymeric surfaces by optimizing different parameters, including power, time, substrate temperature and gas composition. Thereby, the highest immobilization efficiency along with a homogenous biomolecule distribution is achieved with a 5-min plasma treatment under a gas composition of 50% oxygen and nitrogen, at a power of 1000 W and a substrate temperature of 80 °C. These results are also confirmed by different surface characterization methods, including SEM, XPS and contact angle measurements.

Templated electroless nickel deposition for patterning applications

Electroless nickel deposition is a chemical reduction technique commonly used for coating on metals. Deposition on non-metallic substrates is challenging owing to their poor ability to catalyse the reaction. The kinetics data for electroless nickel is limited, especially for different activation techniques. In this work, we show that gold‑palladium sputter activation can be used for electroless nickel growth on glass substrates. Deposition kinetics is measured and compared with standard metallic substrates to elucidate the growth mechanism. By tracking film thickness as a function of temperature and time, we extracted the activation energies for different substrates and surface activation techniques. Activation energy, at a pH of 5.6, for bare SS316 is 3.4 kJ/mol, while for sputter activated substrate it is 73.9 kJ/mol. We also demonstrate that sputter activation can be used to obtain patterned electroless films, by performing lithography assisted area selective deposition and by fabricating a patterned transmission line, with close dimensional tolerance. The process might be extended to other electroless systems as well.

Effect of plasma pretreatment on durability of sol-gel superhydrophobic coatings on laser modified stainless steel substrates

Superhydrophobic surfaces were generated on stainless steel SS 304 substrates, using a combination of physical as well as chemical modification of the surface and tested for use in biomedical applications. Nanosecond pulsed laser was used for physical modification, i.e. creating nanoscaled roughness on the substrates. An additional chemical modification was performed using fluorosilane-based sol-gel nanocomposite coatings to further improve the hydrophobicity. Presently, the key challenge that such surfaces face, is to possess a substantial durability. In this study, a surface activation technique such as plasma pre-treatment was adopted to improve the adhesion of coatings on the laser treated substrates. The coatings deposited using dip coating technique were cured at 150 °C. The surface morphology and the roughness of the processed substrates and the coated samples were characterized using Atomic Force Microscope and Scanning Electron Microscope. The wettability of the surface was monitored and evaluated throughout the study using water contact angle measurements. Weathering tests and scratch resistance measurements using a crockmeter were carried out to evaluate the durability, which revealed that the adhesion could be improved with plasma treatment of the laser textured substrates, prior to coating deposition. Maximum anti-bacterial activity of up to 90% towards the bacterial species Escherichia coli was found on the substrates coated with the fluorosilane-based superhydrophobic coatings for an exposure time of 30 min, without any addition of external anti-bacterial agents. Thus, the preliminary results obtained from the present investigation were found to be promising and were indicative of use of these surfaces for biomedical applications.

Autohesion of polymers

Autohesion (direct-bonding or self-bonding) is the formation of bonds between two surfaces of an identical polymer at elevated temperature (usually just above Tg). It is an emerging technique that has the potential to cleanly and precisely join/bond polymers without the need for adhesives. Autohesion is particularly useful for applications that require hermetic and precise polymer bonding, such as in microfluidics, MEMS, and in the encapsulation of active medical implants. This article discusses the latest debate on the main mechanisms proposed to explain autohesion of polymers such as diffusion, crystalline growth, thermodynamic and chemical bonding. Surface activation techniques that are used to facilitate autohesion such as plasma treatment, chemicals, UV and ozone treatments are explored. In addition, topics such as molecular characteristics of polymers that influence autohesion, limits to bonding strength and hermetic bonding are critically discussed. Methods for evaluating autohesion strength of polymers are also described. Comparisons between prediction models from different research groups with experimental values for authohesive bonding strength are shown. Finally, conclusions and suggestions for further research are presented.

Pd-free surface activation technique for ABS surface metallisation

An environmentally friendly surface etching and Pd free activation technique for acrylonitrile–butadiene–styrene (ABS) surface metallisation was investigated. With surface etching, NiSO4 absorption and NaBH4 reduction, nickel particles were deposited on the ABS surface as a catalyst replacement for palladium catalyst to achieve surface metallisation. After the electroless plating, a uniform copper film was electrodeposited on the ABS surface. The effects of NiSO4 concentration, NaBH4 concentration, reduction temperature and reduction time on the adhesion strength between the ABS surface and the electroless copper film were investigated. The adhesion strengths between electroless copper and ABS substrate reached 0·72 kN m−1, and indicated that this surface activation technique was a feasible and cost effective method for ABS surface metallisation.

Photosensitization of Dye/TiO<sub>2</sub> Thin Films by Using Natural Dye of TCPP

The Dye-Sensitized TiO2 thin film fabricated by TiO2 nanoparticles is a novel technology with advantage in low cost, little pollution and simple in manufacturing process. The fiber-shaped reacting sites provide enlarged photo-sensing area of the TiO2 thin films. Natural dye of TCPP was applied to improve the photo absorbability in this study. Besides, a novel plasma surface activation technique employed on the thin film showed well performance compared with previous reports by heating methods. The SEM images demonstrate that the nano-TiO2 composites deposited on the fiber substrate. Degradation of acetone under 365 and 420 nm light irradiation were conducted to evaluate the photocatalytic ability of the TiO2 and TCPP/TiO2 thin films. While TiO2 thin films gel catalyst showed good photocatalytic performance with a high degradation efficiency of 99.9%, only about 80% conversion efficiency was achieved by the TCPP/TiO2 thin films reactor under 365 nm light irradiation. Although the TCPP dye on TiO2 nanoparticle shows beneficial reflection intensity in 420 nm, the acetone degradation capability of TiO2 and TCPP/ TiO2 thin films reactor decreased about 30% and 25% respectively compared with the degradation efficiency under 365 nm.

Surface activation using remote plasma for silicon to quartz wafer bonding

A pre-wafer-bonding remote-plasma treatment is presented as a route to hydrophilic elevated temperature wafer bonding. This particular remote plasma technique was used as a non-etching surface activation technique. We report a post anneal surface energy of 2,250 mJ/m2 using remote plasma activation which is higher than other reported results. Furthermore, the trend in increasing surface energy with increased with plasma exposure time showed no tail-off. The surface damage present in other plasma techniques is avoided and as a consequence exposure times could be extended. An increase in pre-bonding remote plasma treatment times resulted in increased surface energy, this held true for; initial pre-anneal bonding where van der Waals forces hold the wafers together, for ambient covalent bonding, and, for elevated temperature covalent bonding. It also held true for homo and hetero-wafer bonding. Increased surface energy was evident over a variety of bonding and annealing conditions. Surface energies or more descriptively, bonding energies result are reported for Si to Si and Si to quartz bonding and compared with various other pre-bonding treatments. Attention is focused on results obtained by varying different plasma parameters; exposure time, gas species, etc., and their effect on the surface energy of bonded pair. For silicon to quartz, we report an annealing temperature of 200°C without de-bonding, which is an extension of 50°C over previously reported values. Pre- and post plasma surface roughness measurements were made using an atomic force microscope while bond interface was characterized using scanning acoustic microscopy.

Enhancement of the adhesive force of metal films on PTFE surface achieved by fast-atom-beam surface modification

We tried the method to increase the peel strength between thin film metals and various substrate materials using saddle field fast atom beam (FAB) sources. It is notable that the peel strength was increased more than several times for all substrates than those who were not modified by surface activation using FAB irradiation. Highest peel strength was observed at the coupling of Si and metals in both case of Ar irradiation and SF6 reactive etching by FAB. This surface activation technique was applied to the fabrication of microelectrodes for the detection of mouse nerve signals. The process is expected as one of the available techniques for pre-treatment of the film deposition for several electrical devices.

Vibration Damping on Graphite and KEVLAR(R)Composites Using Piezoceramic Powder Coatings: A Review

Some researchers have studied passive vibration damping using thin hybrid layer(s) of magnetostrictive powder coatings on a wide gamut of composite laminates. Although these magnetostrictive materials can be used for damping of thin flexible structural systems, in practice their use is limited in the domain of microwave spacecraft antenna applications because of electromagnetic interference (EMI) and electromagnetic coupling (EMC) issues at higher transmit and receive radio frequencies (RFs). Ultra-lightweight, high-frequency satellite reflectors made of high specific stiffness/high specific strength graphite and KEVLARcomposites, with stringent precision design requirements with respect to (w.r.t.) the root mean square surface error; pick up post-launch microvibrations in the deployed condition because of the movement of the three-axis gyros of the spacecraft or because of altitude correction exercises along with steep thermal gradients in the space domain. These vibrations at elevated temperatures need to be damped out, particularly in the passive domain, without affecting the overall stability of the spacecraft. Therefore, it is proposed to use particularly non-magnetic, thin hybrid piezoceramic powder coating(s) on one side of the graphite and KEVLAR® composites to cater for the microvibration suppression issue of the spacecraft reflectors. Moreover, at elevated temperatures, the adhesion of thin layers of piezoceramic materials on graphite and KEVLAR® composites also becomes an important issue, which needs to be addressed separately and has been reviewed at length. Therefore, in this paper, an attempt has been made to thoroughly review and investigate experimentally the use of the surface activation technique of RF plasma corona on composites along with coatings of thin hybrid layer(s) of high-sensitivity ferroelectrically soft, non-magnetic piezoelectric ceramic material for achieving passive vibration damping benefits on KEVLAR® and graphite composites with embedded KEVLAR® flexcore at varying temperatures. The surface activation has been performed using the plasma-etching approach to obtain improved adhesion of the piezoceramic material with composites at elevated temperatures. KEVLAR® and graphite composites were treated with RF plasma to modify the surface properties such that they contribute to the adhesion enhancement between plasma-treated polymer surfaces and the piezoceramic material coatings. We have referred to American Society for Testing and Materials (ASTM) standards for the finalization of test specimen sizes for the experimental work. Strain-dependent material damping in the thin piezoceramic passive layers on KEVLAR® and graphite composites leads to a typical nonlinear behavior at varying temperatures. Therefore, an Oberst vibrating beam technique has been chosen for experimentation on a cantilever specimen made of graphite and KEVLAR® in order to estimate the composite loss factor at elevated temperatures. The thin hybrid layer(s) of non-magnetic piezoceramic materials when coated on KEVLAR® and graphite substrates (on one side only) have given improved results w.r.t. passive structural damping at elevated temperatures with almost negligible weight penalty; this is with practically no EMI/EMC issues when tested separately for Ku-band frequencies at the Space Applications Centre, Indian Space Research Organization, Ahmedabad. The encouraging results, w.r.t. the enhanced passive damping at resonant frequencies for piezoceramic powder coated high specific stiffness/high specific strength graphite and KEVLAR® composites at elevated temperatures, may make the present investigation and review on piezocoated composites a possible candidate for high-frequency applications in future w.r.t. the microvibrations experienced in orbit by the reflectors of today's sophisticated Earth observation satellites, which are designed for stringent pointing accuracies and resolutions.

Increasing of gas nitriding kinetics via surface pre-treatment

The possibility of an increase of gas nitriding kinetics was studied. The duration of the first stage of the nitride layer formation, plays a significant role in the overall treatment time. To shorten this time surface activation techniques are used. In the present work cathode sputtering was investigated as a surface activation technique. The investigation was carried out on iron. The cathode sputtering process was performed in a separate chamber under argon atmosphere with the following parameters: voltage 700–1350 V, current density 1–4 mA/cm 2 and time 10–60 min. The sample was connected as a cathode and after exposition was introduced into the furnace reaction zone where gas nitriding was carried out in an ammonia atmosphere. The thickness of the compound case and internal diffusion zone were compared for specimens pre-treated and non-pre-treated before gas nitriding. Moreover, changes in the upper surface of iron after cathode sputtering were investigated. It has been stated that cathode sputtering increases the kinetics of nitride layer formation even if the neutral gas is used for sputtering. Also, some mathematical relationships between thickness of nitride layer and cathode sputtering parameters were found.

Micromechanism fabrication using silicon fusion bonding

Silicon fusion bonding is studied as an enabling technology for the fabrication of microrobotic mechanisms. The effects of both surface activation technique and annealing temperature on bond strength are considered using a crack-opening technique. As part of the study, the relationship between patterned silicon feature size and the resulting bond strength is explored. Based on the experimental results, recommendations for an optimal silicon fusion bonding process for micromechanism fabrication are presented. The experimental results indicate that bulk silicon bonding strength can be achieved independent of feature size at temperatures as low as 300°C, with positive implications for micromechanism fabrication.

28.1: Novel 20‐inch Color Field Emission Display Prototype

AbstractThe fabrication processes and the display characteristics of color field emission display (FED) with screen diagonal of 20‐ inch were described. FEDs were developed with thin film, screen‐print and surface activation techniques. They could display Chinese characters, English letters and simple cartoon images in 50 Hz. The pixel size of FED prototype was 0.15×0.5 mm2 for color FED or 0.5×0.5 mm2 for monochrome FED. The pixel number was 358×358×3 for color FED or 358×358 for monochrome FED. The thickness of FED panel was about 2.2 mm. Under about 300V anode bias, the maximum emission current of one pixel of monochrome FED was about 26 mA and the screen brightness of monochrome FED with conventional CRT phosphors was 300 cd/m2.