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The proliferation of electronic devices has made electromagnetic interference (EMI) shielding an exponentially growing business. Regulatory requirements change constantly as new technologies continue to emerge. Innovations in materials and new advances in shielding implementation techniques are needed to pass regulatory compliance tests at an affordable cost. Here, we print various EMI shielding materials such as copper, silver and a composite of copper with Fe3O4 using plasma jet printing. Printing enables shields only a few microns thick capable of high shielding effectiveness. Copper’s EMI shielding performance is primarily contributed by reflection mechanism, as expected and this is known to cause secondary pollution. A Green Index for EMI shielding, given by the ratio of absorption and reflection contributions to shielding, indicates values lower than 0.1 for printed copper films.

An atmospheric pressure plasma based printer is described as an alternative to conventional techniques including inkjet printing. The approach is demonstrated to be capable of printing various nanomaterials, and adjusting the plasma parameters, carrier gas flows and the physical parameters of the inks or nanomaterial suspensions can optimize the print quality. Raman analysis was used to characterize the oxide materials and carbon nanotubes printed using this technique, revealing high quality prints. The printed carbon nanotubes were used in a gas sensor chip and shown to provide good ammonia detection capability.

The emerging Internet of things (IoT) demands not only new device technologies but also strengthening the security of things in order to prevent tampering and hacking. Humans have unique characteri...

Printing of metallic, semiconducting and other materials is a key step in printed and flexible electronics. Plasma jet printing is emerging as an alternative to inkjet, aerosol and other competing printing techniques since it is a single step process that does not require post-thermal annealing to obtain consolidated printed films with good adhesion. Here, we provide results for printing metallic films and patterns from flight tests with varying gravity from 0 to 2 G. The conductivity of the as-printed silver film without any post-sintering was 12% of the bulk value for silver. As expected, the absence of gravity has no adverse impact on the print quality since the ink content along with the plasma is forcefully ejected by the applied electric field towards the substrate, while the successful flight test itself attests to the robustness of the printer and the printing technique.

Miniaturization of electronic devices and the advancement of Internet of Things pose exciting challenges to develop technologies for patterned deposition of functional nanomaterials. Printed and flexible electronic devices and energy storage devices can be embedded onto clothing or other flexible surfaces. Graphene oxide (GO) has gained much attention in printed electronics due its solution processability, robustness, and high electrical conductivity in the reduced state. Here, we introduce an approach to print GO films from highly acidic suspensions with in situ reduction using an atmospheric pressure plasma jet. Low temperature plasma of a He and H2 mixture was used successfully to reduce a highly acidic GO suspension (pH < 2) in situ during deposition. This technique overcomes the multiple intermediate steps required to increase the conductivity of deposited GO. X-ray spectroscopic studies confirmed that the reaction intermediates and the concentration of oxygen functionalities bonded to GO have been reduced significantly by this approach without any additional steps. Moreover, the reduced GO films showed enhanced conductivity. Hence, this technique has a strong potential for printing conducting patterns of GO for a range of large-scale applications.

Controlled integration of features that enhance the analytical performance of a sensor chip is a challenging task in the development of paper sensors. A critical issue in the fabrication of low-cost biosensor chips is the activation of the device surface in a reliable and controllable manner compatible with large-scale production. Here, we report stable, well-adherent, and repeatable site-selective deposition of bioreactive amine functionalities and biorepellant polyethylene glycol-like (PEG) functionalities on paper sensors by aerosol-assisted, atmospheric-pressure, plasma-enhanced chemical vapor deposition. This approach requires only 20 s of deposition time, compared to previous reports on cellulose functionalization, which takes hours. A detailed analysis of the near-edge X-ray absorption fine structure (NEXAFS) and its sensitivity to the local electronic structure of the carbon and nitrogen functionalities. σ*, π*, and Rydberg transitions in C and N K-edges are presented. Application of the plasma-processed paper sensors in DNA detection is also demonstrated.

Atmospheric pressure plasmas have gained attention in recent years for several environmental applications. This technology could potentially be used to deactivate airborne microorganisms, surface-bound microorganisms, and biofilms. In this work, the authors explore the efficacy of the atmospheric pressure dielectric barrier discharge (DBD) to inactivate airborne Staphylococcus epidermidis and Aspergillus niger that are opportunistic pathogens associated with nosocomial infections. This technology uses air as the source of gas and does not require any process gas such as helium, argon, nitrogen, or hydrogen. The effect of DBD was studied on aerosolized S. epidermidis and aerosolized A. niger spores via scanning electron microscopy (SEM). The morphology observed on the SEM micrographs showed deformations in the cellular structure of both microorganisms. Cell structure damage upon interaction with the DBD suggests leakage of vital cellular materials, which is a key mechanism for microbial inactivation. The chemical structure of the cell surface of S. epidermidis was also analyzed by near edge x-ray absorption fine structure spectroscopy before and after DBD exposure. Results from surface analysis revealed that reactive oxygen species from the DBD discharge contributed to alterations on the chemistry of the cell membrane/cell wall of S. epidermidis.Atmospheric pressure plasmas have gained attention in recent years for several environmental applications. This technology could potentially be used to deactivate airborne microorganisms, surface-bound microorganisms, and biofilms. In this work, the authors explore the efficacy of the atmospheric pressure dielectric barrier discharge (DBD) to inactivate airborne Staphylococcus epidermidis and Aspergillus niger that are opportunistic pathogens associated with nosocomial infections. This technology uses air as the source of gas and does not require any process gas such as helium, argon, nitrogen, or hydrogen. The effect of DBD was studied on aerosolized S. epidermidis and aerosolized A. niger spores via scanning electron microscopy (SEM). The morphology observed on the SEM micrographs showed deformations in the cellular structure of both microorganisms. Cell structure damage upon interaction with the DBD suggests leakage of vital cellular materials, which is a key mechanism for microbial inactivation. The c...

The surface properties of the electrode materials play a crucial role in determining the performance and efficiency of energy storage devices. Graphene oxide and nanostructures of 3d transition metal oxides were synthesized for construction of electrodes in supercapacitors, and the electronic structure and oxidation states were probed using near-edge X-ray absorption fine structure. Understanding the chemistry of graphene oxide would provide valuable insight into its reactivity and properties as the graphene oxide transformation to reduced-graphene oxide is a key step in the synthesis of the electrode materials. Polarized behavior of the synchrotron X-rays and the angular dependency of the near-edge X-ray absorption fine structures (NEXAFS) have been utilized to study the orientation of the σ and π bonds of the graphene oxide and graphene oxide–metal oxide nanocomposites. The core-level transitions of individual metal oxides and that of the graphene oxide nanocomposite showed that the interaction of graphene oxide with the metal oxide nanostructures has not altered the electronic structure of either of them. As the restoration of the π network is important for good electrical conductivity, the C K edge NEXAFS spectra of reduced graphene oxide nanocomposites confirms the same through increased intensity of the sp2-derived unoccupied states π* band. A pronounced angular dependency of the reduced sample and the formation of excitonic peaks confirmed the formation of extended conjugated network.

This study presents the morphological and chemical modification of the cell structure of aerosolized Escherichia coli treated with a dielectric barrier discharge (DBD). Exposure to DBD results in severe oxidation of the bacteria, leading to the formation of hydroxyl groups and carbonyl groups and a significant reduction in amine functionalities and phosphate groups. Near edge x-ray absorption fine structure (NEXAFS) measurements confirm the presence of additional oxide bonds upon DBD treatment, suggesting oxidation of the outer layer of the cell wall. Electron microscopy images show that the bacteria undergo physical distortion to varying degrees, resulting in deformation of the bacterial structure. The electromagnetic field around the DBD coil causes severe damage to the cell structure, possibly resulting in leakage of vital cellular materials. The oxidation and chemical modification of the bacterial components are evident from the Fourier transform infrared spectroscopy and NEXAFS results. The bacterial reculture experiments confirm inactivation of airborne E. coli upon treating with DBD.

Herein we report on a preparation and performance of stable, hydrophilic and biocompatible polymeric material suitable for functionalization of disposable substrates used in biosensors. This new material features -COOH surface groups cross-linked with ethylene glycol molecules and was prepared in situ on disposable, plastic substrate by high-throughput and environmentally friendly technique called plasma-enhanced chemical vapor deposition (PECVD). The film is grafted to the plasma activated plastic by sequential deposition of tetraethylorthosilicate, forming a bonding layer, and mixed vapors of acrylic acid and diethyleneglycol dimethylether (AA/PEG) that provide the desired functional groups forming a sensing, contact layer. A superior performance of the AA/PEG coating as suitable material for substrates in biomedical devices was demonstrated in a model fluorescence linked immunosorbent assay. The results were compared with other commonly used surface materials prepared by wet chemistry methods. The unique characteristic of the AA/PEG film is that the immunoassay can be executed without the need for a blocking step, typically using albumins, without negative consequences on the bioassay results. In fact, the superior quality of the materials modified with AA/PEG film was highlighted by improving the sensitivity of an immunoassay by two orders of magnitude when compared with substrates prepared by standard surface chemistry methods. Copyright © 2011 Wiley Periodicals, Inc.

We report a method for studying nanoparticle-biosensor surface interactions based on total internal reflection fluorescence (TIRF) microscopy. We demonstrate that this simple technique allows for high throughput screening of non-specific adsorption (NSA) of nanoparticles on surfaces of different chemical composition. Binding events between fluorescent nanoparticles and functionalized Zeonor® surfaces are observed in real-time, giving a measure of the attractive or repulsive properties of the surface and the kinetics of the interaction. Three types of coatings have been studied: one containing a polymerized aminosilane network with terminal -NH2 groups, a second film with a high density of -COOH surface groups and the third with sterically restraining branched poly(ethylene)glycol (PEG) functionality. TIRF microscopy revealed that the NSA of nanoparticles with negative surface charge on such modified coatings decreased in the following order -NH2>-branched PEG>-COOH. The surface specificity of the technique also allows discrimination of the degree of NSA of the same surface at different pH. © 2010 Elsevier Inc.

The performances of new polymeric materials with excellent optical properties and good machinability have led the biomedical diagnostics industry to develop cheap disposable biosensor platforms appropriate for point of care applications. Zeonor, a type of cycloolefin polymer (COP), is one such polymer that presents an excellent platform for biosensor chips. These polymer substrates have to be modified to have suitable physico-chemical properties for immobilizing proteins. In this work, we have demonstrated the amine functionalization of COP substrates, by plasma enhanced chemical vapour deposition (PECVD), through codeposition of ethylene diamine and 3-aminopropyltriethoxysilane precursors, for building chemistries on the plastic chip. The elemental composition, adhesion, ageing and reactivity of the plasma polymerized film were examined. The Si-O functionality present in amino silane contributed for a good interfacial adhesion of the coating to COP substrates and also acted as a network building layer for plasma polymerization. Wet chemical modification was then carried out on the amine functionalized chips to create chemically reactive isothiocyanate sites and protein repellent fluorinated sites on the same chip. The density of the reactive and repellent sites was altered by choosing appropriate mixtures of homofunctional phenyldiisothiocyanate (PDITC), pentafluoroisothiocyanate (5FITC) and phenylisothiocyanate (PITC) compounds. By tailoring the density of reactive binding sites and protein repellent sites, the non-specific binding of ssDNA has been decreased to a significant extent. © 2010 Elsevier B.V.

The success of a biomaterial depends on the nature of interaction and the progressive reaction between the biological components and the surface of the biomaterial. In order to control the interaction between the biomaterial and biological component, it is necessary to understand the factors that influence the protein adsorption and cell proliferation. Surface chemistry plays a crucial role in the success of any blood contacting biomaterial. Plasma enhanced chemical vapour deposition (PECVD) is an interesting commonly used technique for tailoring surface characteristics while retaining bulk material properties. Two different films, namely polymer-like and silica-like coatings, with varying surface characteristics have been deposited from hexamethyldisiloxane, by PECVD, on 316L stainless steel. A correlation between the bulk plasma, interfacial adhesion of the coating to 316L steel, surface characteristics and biomolecule interaction is presented in this work The interfacial adhesion strength analysis demonstrated that silica-like coatings have higher adhesion strength to 316L stainless steel than polymer-like coatings, caused due to the formation of a strong Fe-O-Si and Cr-O-Si bonds. It was observed that the effect of nanoscale surface roughness (dose to 6 nm) was less significant, and that the surface chemistry played a significant role in governing the fibrinogen adsorption. Highest fibrinogen adsorption on plain steel was due to the electrostatic interaction of the metal oxide layer with the protein Hydrophobicity of the polymer like film resulted in a higher fibrinogen binding than the silica-like films.

Silicon dioxide and titanium dioxide films show varying biocompatible characteristics when used as a passive biocompatible coating for an implant. The difference in their behaviour in biological environment is due to many factors like surface energy, surface charge, semi-conducting nature, surface roughness, coefficient of friction, etc. Surface wettability of the film plays a key role in determining the biocompatible characteristics of the film. In this work films with a range of water contact angle have been deposited on 316L stainless steel with enhanced adhesion strength and good stability in biological media. SiOx, TiOx and SiO-TiO mixed oxide films have been deposited by PECVD for this purpose. The water contact angle of the films ranges from 105° for polymer-like films to 24° for titanium oxide films. Intermediate values of contact angle of 60° for SiOx down to 38° could be obtained from mixed oxide films by controlling the precursor ratio and RF power. The structure of the film is analysed by FT-IR spectroscopic measurements. The adhesion strength is measured for various pre-treatment times by using a pull-off adhesion tester. The stability of the films in biological media is analysed by using an optical microscope. The adhesion and stability are improved by the combination of pre-treatment and layered film deposition.

We present a novel approach for the room-temperature fabrication of conductive traces and their subsequent site-selective dielectric encapsulation for use in flexible electronics. We have developed an aerosol-assisted atmospheric pressure plasma-based deposition process for efficiently depositing materials on flexible substrates. Silver nanowire conductive traces and silicon dioxide dielectric coatings for encapsulation were deposited using this approach as a demonstration. The paper substrate with silver nanowires exhibited a very low change in resistance upon 50 cycles of systematic deformation, exhibiting high mechanical flexibility. The applicability of this process to print conductive traces on nonconformal 3D objects was also demonstrated through deposition on a 3D-printed thermoplastic object, indicating the potential to combine plasma printing with 3D printing technology. The role of plasma here includes activation of the material present in the aerosol for deposition, increasing the deposition rate, and plasma polymerization in the case of inorganic coatings. The demonstration here establishes a low-cost, high-throughput, and facile process for printing electronic components on nonconventional platforms.

Recently, there have been enormous efforts to tailor the properties of graphene. These improved properties extend the prospect of graphene for a broad range of applications. Plasmas find applications in various fields including materials science and have been emerging in the field of nanotechnology. This review focuses on different plasma functionalization processes of graphene and its oxide counterpart. The review aims at the advantages of plasma functionalization over the conventional doping techniques. Selectivity and controllability of the plasma techniques opens up future pathways for large scale, rapid functionalization of graphene for advanced applications. We also emphasize on atmospheric pressure plasma jet as the future prospect of plasma based functionalization processes.

Recent interest in flexible electronics and wearable devices has created a demand for fast and highly repeatable printing processes suitable for device manufacturing. Robust printing technology is critical for the integration of sensors and other devices on flexible substrates such as paper and textile. An atmospheric pressure plasma-based printing process has been developed to deposit different types of nanomaterials on flexible substrates. Multiwalled carbon nanotubes were deposited on paper to demonstrate site-selective deposition as well as direct printing without any type of patterning. Plasma-printed nanotubes were compared with non-plasma-printed samples under similar gas flow and other experimental conditions and found to be denser with higher conductivity. The utility of the nanotubes on the paper substrate as a biosensor and chemical sensor was demonstrated by the detection of dopamine, a neurotransmitter, and ammonia, respectively.

Herein a simple analytical method is presented for the characterization of biomolecule adsorption on cyclo olefin polymer (COP, trade name: Zeonor®) substrates which are widely used in microfluidic lab-on-a-chip devices. These Zeonor® substrates do not possess native functional groups for specific reactions with biomolecules. Therefore, depending on the application, such substrates must be functionalized by surface chemistry methods to either enhance or suppress biomolecular adsorption. This work demonstrates a microfluidic method for evaluating the adsorption of antibodies and oligonucleotides surfaces. The method uses centrifugal microfluidic flow-through chips and can easily be implemented using common equipment such as a spin coater. The working principle is very simple. The user adds 40L of the solution containing the sample to the starting side of a microfluidic channel, where it is moved through by centrifugal force. Some molecules are adsorbed in the channel. The sample is then collected at the other end in a small reservoir and the biomolecule concentration is measured. As a pilot application, we characterized the adsorption of goat anti-human IgG and a 20-mer DNA on Zeonor®, and on three types of functionalized Zeonor: 3-aminopropyltriethoxysilane (APTES) modified surface with mainly positive charge, negatively charged surface with immobilized bovine serum albumin (BSA), and neutral, hydrogel-like film with polyethylene glycol (PEG) characteristics. This simple analytical approach adds to the fundamental understanding of the interaction forces in real, microfluidic systems. This method provides a straightforward and rapid way to screen surface compositions and chemistry, and relate these to their effects on the sensitivity and resistance to non-specific binding of bioassays using them. In an additional set of experiments, the surface area of the channels in this universal microfluidic chip was increased by precision milling of microscale trenches. This modified surface was then coated with APTES and tested for its potential to serve as a unique protein dilution feature. © 2012 Elsevier B.V.

We report the controlled diffusion of gas-phase high-reactivity chemical species into long polymeric microcavities to form glass-like, low-permeability barrier films on the interior surfaces of the microcavities. Reactive species created from fragmentation of O(2) and hexamethyldisiloxane (HMDSO) in a radio-frequency (RF) plasma environment are allowed to diffuse into the microcavities of polydimethylsiloxane (PDMS), where surface reactions lead to the formation of an effective, glass-like thin-film barrier. Reactive species including silicon radicals and elemental oxygen maintain their reactivity for sufficient times (up to 7000 s) and survive the random diffusional walk through the microcavities to form glass barriers as much as 65 mm from the cavity entrance. The barrier thickness and the growth length can be controlled by the reaction time and chamber operating pressure. Increasing the cross sectional area of the cavity inlet and/or decreasing the mean free path was found to increase the thickness of the barrier film. Optical emission spectroscopic analysis was used to characterize the reactive fragments formed from HMDSO, and energy-dispersive X-ray analysis revealed that the barrier composition is consistent with oxides of silicon (SiO(x)). Formed inside PDMS microcavities, the glass barrier blocks the penetration or absorption of small molecules such as rhodamine B (RhB) and biotin, and also resists permeation of organic solvents such as toluene, preventing the PDMS microfluidic structures from swelling and deforming. Moreover, formation of glass-like thin films in PDMS microcavities enhances the stability of electroosmotic flow (EOF) relative to uncoated PDMS devices, in which EOF instabilities are significant; this enables separation by electrophoresis with reproducibility (relative standard deviation 3%, n = 5) and baseline peak resolution (R:1.3) comparable to that obtained in conventional fused-silica capillaries.

We report on the direct formation of phase pure nanocrystalline cuprous oxide (Cu2O) film with band gap ~ 2 eV by microwave plasma oxidation of pulsed dc magnetron sputtered Cu films and the highly controlled oxidation of Cu in to Cu2O and CuO phases by controlling the plasma exposure time. The structural, morphological and optoelectronic properties of the films were investigated. p-type Cu2O film with a grain size ~ 20–30 nm, resistivity of ~ 66 Ω cm and a hole concentration of ~ 2 × 1017 cm− 3 is obtained for a plasma exposure time of 10 min without using any foreign dopants. The optical absorption coefficient (~ 105 cm− 1) of the Cu2O film is also reported.

Figure Presented: The surface functionalization of a noble metal is crucial in a surface plasmon resonance-based biomolecular detection system because the interfacial coating must retain the activity of immobilized biomolecules while enhancing the optimal loading. We present here a one-step, room-temperature, high-speed, gas-phase plasma polymerization process for functionalizing gold substrates using siloxane as an adhesion layer and acrylic acid as a functional layer. Siloxane- and thiol-based coatings were compared for their performance as adhesion and the interfacial layer for subsequent functionalization. An in situ sequential deposition of siloxane and acrylic acid resulted in a 7-fold increase in carboxylic functionality surfacial content compared to films deposited with thiol-containing precursors. Grading of the layer composition achieved as a consequence of ion-induced mixing on the surface coating under the application of the plasma is confirmed through secondary ion mass spectroscopic studies. DNA hybridization assays were demonstrated on gold/glass substrates using surface plasmon enhanced ellipsometry and the applicability of this coating for protein immunoassays were demonstrated with plasma functionalized gold/plastic substrates in Biacore 3000 SPR instrument. © 2011 American Chemical Society.

In early stage disease diagnosis, an accurate and reliable measurement of low concentrations of specific biomarkers is a key need. The detection technique requires the reaction of an antibody, which is generally covalently bound to the biosensor platform, with its antigen. The application of Zeonor ®, a cyclo olefin copolymer (COP) with very low autofluorescence, good optical properties and high precision molding characteristics, as a biosensor platform has been demonstrated recently. Highly reproducible, industrial scale surface chemical modification of the COP plastic for covalent attachment of the biomolecules for specific recognition of the target, together with low non-specific binding of other proteins that may be present in the sample is a key challenge. In this work, the applicability of plasma enhanced chemical vapor deposition (PECVD) process has been demonstrated by depositing varying surface functionalities including amines, carboxylic, mercapto, epoxy and polyethylene glycol functionalities. The plasma functionalized coatings thus created possess both reactive and repellent sites on the biosensor chip, allowing the chip to be configured either for fluorescence or light scattering-based detection or for label-free surface plasmon resonance detection techniques. The versatility of the gas phase deposition process for building sequential chemistries on low cost and disposable plastic chips is presented in detail. © 2011 Elsevier Ltd. All rights reserved.

Poly(methyl methacrylate) (PMMA) flow-cells containing microwells were deposited with different nonspecific binding blocking agents, namely, bovine serum albumin (BSA), cationic lipid (DOTAP:DOPE) and diethylene glycol dimethyl ether (DEGDME). Water contact angle (WCA) and atomic force microscope (AFM) measurements were carried out to confirm the successful depositions of BSA, DOTAP, and DEGDME onto the PMMA surfaces. Fluorescent intensity measurements were performed to evaluate the degree of nonspecific adsorption of Cy5-labeled anti-IgG proteins onto plain and oxygen plasma-treated (PT) PMMA flow-cells as well as PMMA flow-cells deposited with different above-mentioned blocking agents. We then employed a label-free detection method called total internal reflection ellipsometry (TIRE) to evaluate the stability of the deposited blocking agents inside the PMMA flow-cells. It was found that, while DOTAP:DOPE was the best agent for blocking the nonspecific adsorption, it could be removed from the PMMA surfaces of the flow-cells upon rinsing with phosphate buffered saline (PBS) and later deposited back onto the Au-coated glass sensing substrate of the TIRE. The removal of the blocking agents from PMMA surfaces and their deposition onto the sensing substrate were further manifested by measuring the kinetics and the amount of adsorbed anti-α-hCG proteins. Overall, the dry DEGDME coating by plasma-enhanced chemical vapor deposition (PECVD) showed very good blocking and excellent stability for subsequent assay inside the microwells. Our results could be useful when one considers what blocking agents should be used for PMMA-based microfluidic immunosensor or biosensor devices by looking at both the blocking efficiency and the stability of the blocking agent. © 2011 American Chemical Society.

The surface science of bioassay devices is of great importance in the development of modern diagnostic platforms. The quality of surface is one of the most important elements of the device, often governing the background response, hence controlling the sensitivity of an assay. Detailed surface characterization and analysis are imperative for the preparation of reproducible coatings with desired properties. We performed a comprehensive characterization of 3-aminopropyl-triethoxysilane films prepared under two different deposition conditions on COP slides. Two sets of slides were prepared, by exposing them to plasma reaction for 30 seconds (A30 slide) and 4 minutes (A4 slide). While the variations in the deposition conditions seemed very subtle, the use of several powerful analytical tools helped us to reveal some fundamental differences between the studied films in terms of binding capacity, swelling and adhesion. Overall, the A30 films, with a thickness of 5.12 nm, showed up to 40% higher binding capacity and 25% better adhesion than the thicker A4 coatings (28.15 nm). Upon contact with aqueous media, a significant change was observed in terms of surface roughness. The A30 slides outperformed A4 slides, resulting in smoother surface, which is an important parameter for biomolecule immobilisation. The use of the techniques described in this article is aimed to set new standards for the characterization and analysis of the substrate surface of the future diagnostic devices. © The Royal Society of Chemistry 2010.

Many current designs in biomedical diagnostics devices are based on the use of low cost, disposable, easy-to-fabricate chips made of plastic material, typically a cyclo-olefin polymer (COP). Low autofluorescence properties of such material, among others, make it ideal substrate for fluorescence-based applications. Functionalization of this plastic substrate for biomolecule attachment is therefore of great importance and the quality of films produced on such surface have often a significant influence on the performance of the device. In this communication we discuss the surface chemistry and some other characteristics of hydrophilic films, containing carboxylic acid functional groups, formed by plasma oxidation of COP and also films containing cross-linked, polymerized acryclic acid produced by sequential deposition of tetraorthosilicate and acrylic acid by plasma enhanced chemical vapor deposition (PECVD). Immobilization of labeled, single stranded DNA revealed high binding capacity for both coatings. To our best knowledge, this is the first example of direct immobilization of biomolecules on just plasma oxidized COP. Furthermore, more sophisticated treatment of the oxidized plastic substrate by PECVD with other organic precursors increased the binding capacity by some 40% than that of just plasma oxidized COP. The carboxy functionalized surfaces, due to the negative charge of the carboxy groups, showed very positive trends towards increasing the signal to noise ratio when charged biomolecules such as DNA, are used. © 2010 Elsevier B.V.

In this paper, a new, fast, reproducible technique for atomic force microscopy (AFM) tips functionalization used for chemical interaction measurements is described. Precisely, the deposition of an aminated precursor is performed through plasma-enhanced chemical vapor deposition (PECVD) in order to create amine functional groups on the AFM tip and cantilever. The advantages of the precursor, aminopropyltriethoxysilane (APTES), were recently demonstrated for amine layer formation through PECVD deposition on polymeric surfaces. We extended this procedure to functionalize AFM probes. Titration force spectroscopy highlights the successful functionalization of AFM tips as well as their stability and use under different environmental conditions. © 2010 Elsevier Inc.

Here we have demonstrated a solventless plasma-based process that integrates low-cost, high throughput, high reproducibility and ecofriendly process for the functionalization of the next-generation point-of-care device platforms. Amine functionalities were deposited by plasma-enhanced chemical vapour deposition (PECVD) using a new precursor. The influence of the plasma RF power and the deposition time on surfacial properties, as well as their effect on the reactivity and content of amino groups was investigated. The key process determinants were to have a sufficient power in the plasma to activate and partially fragment the monomer but not too much as to lose the reactive amine functionality, and sufficient deposition time to develop a reactive layer but not to consume or erode the amine reactivity. An immunoassay performed using human immunoglobulin (IgG) as a model analyte showed an improvement of the detection limit by two orders of magnitude beyond that obtained using devices activated by liquid-phase reaction. © 2010 Elsevier B.V. All rights reserved.

We describe a method to form glass like thin film barrier in polydimethylsiloxane (PDMS) microcavities. The reactive fragments for the surface reaction were created from O 2 and hexamethyldisiloxane (HMDS) in RF plasma environment. The reaction is based on migration of the reactive fragments into the microcavities by diffusion, to form a glass like thin film barrier to conceal the naked surface of PDMS. The barrier successfully blocked penetration of a fluorescent dye rhodamine B (RhB) into PDMS. The thickness of the barrier could be controlled by the time of reaction and the pressure inside the reaction chamber. There is a wide range of applications of such a technique in various fields, e.g. for coating the covered surfaces of microfluidic channels, tubes, capillaries, medical devices, catheters, as well as chip-integrated capillary electrophoresis and advanced electronic and opto-fluidic packaging.

The modification of cyclo-olefin polymer Zeonor by plasma-enhanced chemical vapor deposition to form a silica-like surface and evaluation of its application for lateral flow bioassays applications are discussed in this study. The SiOx layer was extensively characterized using contact angle measurements, atomic force microscopy, and Fourier transform infrared spectroscopy in attenuated total internal reflectance mode where the presence of a uniform SiOx film was clearly identified. The SiOx modification resulted in a surface with enhanced wettability and excellent fluidic properties when combined with a hot-embossed micropillar capillary fill-based substrate. The SiOx surface also had the ability to accelerate the clotting of human plasma, which may have application in certain types of blood coagulation assays.

This paper presents a very simple, industrially scalable method for transferring a high-resolution, biologically active protein pattern from one substrate to another. We demonstrate the transfer of a protein pattern formed initially by microcontact printing from a silicon surface (to which this form of printing is applicable) onto a glass or polymer substrate, almost independently of the surface/bulk properties of the second substrate. A very thin, spin-coated layer of a sugar is used to preserve the structure and organization of proteins during the subsequent plasma deposition of a siloxane polymer, after which the protein pattern could simply be peeled off the silicon substrate and glued onto any other desired substrate. © 2009 Elsevier B.V. All rights reserved.

This work reports the fabrication of a biosensing chip surface designed for plasmonic detection, and features a layer of noble metal nanoparticles encapsulated as a sandwich within amine-functionalized polysiloxane layers formed by plasma-enhanced chemical vapour deposition. The collective surface plasmon resonance (CSPR) phenomenon characteristic of a dense particle layer is demonstrated for encapsulated gold nanoparticles of different diameters. Biomolecular immobilization is carried out through the amine functional groups that are part of the encapsulating layer. The detection of biomolecular binding events at the sensor surface is demonstrated both by a shift in resonance wavelength at constant angle of incidence using SPR-enhanced spectroscopic ellipsometry and by detecting the angular shift in resonance in a commercial SPR instrument (Biacore®). Taken with other results, this work shows how a complete SPR chip can be assembled by a rapid sequence of operations in a single plasma chamber.

A label-free biosensor is presented using carbon nanofiber (CNF) nanoelectrode arrays for the detection of cardiac troponin-I in the early diagnosis of myocardial infarction. Immobilization of anti-cTnI Ab on CNFs and the detection of human-cTnI were examined using electrochemical impedance spectroscopy and cyclic voltammetry techniques. Each step of the modification process was monitored, and the results show changes in electrical capacitance or resistance to charge transfer due to the specificity of corresponding adsorption of Ab–Ag interaction. The immunosensor demonstrates a good selectivity and high sensitivity against human-cTnI analytes and is capable of detecting cTnI at concentrations as low as ∼0.2 ng/mL, which is 25 times lower than that possible by conventional methods. Analysis of the electrode at various stages using atomic force microscopy and X-ray reflectivity provides information on the surface roughness and orientation of the antibody.

Aerosol assisted atmospheric pressure plasma based room temperature deposition and patterning of metal nanostructures using a colloidal gold precursor are presented. The distribution and monodispersity of the deposited nanoparticles were evident from the scanning electron microscopic image and UV-Vis absorbance band. Micropatterning of highly monodispersed metal nanoparticles is also demonstrated. It is observed that by varying the plasma process parameters the density of packing of gold nanoparticles could be varied significantly and hence the plasmonic band could be tailored.

Silver thin films are well known as the most sensitive material for surface plasmon resonance (SPR) based analysis. However, the use of silver for this purpose is limited by three main issues, namely poor adhesion to plastic substrates, chemical instability in both air and aqueous environments and hence the difficulty in functionalizing the silver coated substrate for immobilizing biomolecular ligands by conventional liquid phase methods. In this work, we have successfully addressed these problems using gas-phase coating processes. We demonstrate highly adherent sputter-deposited silver coatings on low cost polymer substrates using a sputter-deposited thin gold adhesion layer. The problems of chemical instability and functionalisation have been addressed by using the gas phase process of plasma enhanced chemical vapour deposition (PECVD) to deposit thin films with a base SiO(x)C(y)H(z) layer (using tetraethyl orthosilicate precursor) functionalised with carboxylic acid (from sequential deposition with acrylic acid precursor). The resultant coating serves as a protective layer against degradation of the optical properties of silver under long term storage and use in ambient conditions. The reactive carboxyl functionality is used for the covalent immobilization of biomolecules. The successful stabilisation and functionalization of silver films on plastic sensor chips is demonstrated by mouse IgG immunoassays. The expected superior performance of the silver thin films over gold thin films for SPR analysis is demonstrated.

Point-of-care (POC) diagnostics implementing microfluidic technology on single use disposable plastic chips has potential applications in personalized medicine, clinical diagnostics and global health. However, the challenges in commercializing POC devices must be addressed. Immobilization of biomolecules to plastic chips through appropriate surface functionalization is a key issue for the fabrication of new generation biomedical diagnostic devices. The most important requirements for a practicable surface functionalization process are speed, control and reliability. Plasma-based methods can meet these criteria. A single step, solventless, ecofriendly and high throughput nature of plasma processing makes them highly attractive. Here we demonstrate the efficient surface functionalization of a next-generation biosensor material, a chemically inert cycloolefin polymer (COP). The plasma formation of a surface-bound aminated siloxane network from mixed aminopropyltriethoxysilane and ethylenediamine precursors allowed us to form a well-adherent film with an exceptionally high degree of amine functionalization. We deduce that the siloxane was the critical component for radical insertion into the COP and for building a stable network to support the reactive amine functionalities. We present a full physical and chemical characterization of the films, including a detailed study of their swelling in water, using an array of surface analytical techniques: X-ray photoelectron spectroscopy, X-ray reflectivity, reflection infra-red spectroscopy, atomic force microscopy (AFM) and fluorophore binding reactions. We demonstrate an original approach for qualitatively analyzing the distribution of amine functionalities by counting surface-bound functionalized silica nanoparticles in the AFM. The relative contributions from covalent (specific) and non-covalent (non-specific) reaction chemistry assessed using 3�-fluorescein-labeled ssDNA attachment showed that the non-specific binding could be reduced significantly according to the particular feed gas mixture used to prepare the coating. A reaction mechanism has been proposed for the deposition of amine functionalities on COP plastic and also for enhancing the amine functionalities that affect the non-specific binding significantly. © 2010 The Royal Society of Chemistry.

Corrigendum to “Influence of ion bombardment on the surface functionalization of plasma deposited coatings” [Surface & Coatings Technology. Volume 203 (2009) p. 3521–3526] R.P. Gandhiraman ⁎, S.K. Karkari , S.M. Daniels , Brian D. MacCraith a a Biomedical Diagnostics Institute, Dublin City University, Dublin-9, Ireland b National Centre for Plasma Science and Technology, Dublin City University, Dublin-9, Ireland