Wettability plays a key role in multiphase fluid flow through porous media, significantly influencing geological processes such as CO2 sequestration, groundwater remediation, or oil recovery. Micromodels, i.e. microfluidic porous media, have advanced the study of fluid flows in porous media by enabling direct visualisation of these processes. However, the influence of wettability heterogeneities on fluid flows in porous media remains underexplored in the literature, with studies focusing primarily on homogeneous wettabilities. In this study, we propose a complete method to manufacture micromodels with controllable, heterogeneous wettabilities. This work is at the crossroads of three different fields: microfabrication, surface treatment and fluid transport in porous media. The micromodels are made from a transparent polymer, cyclic olefin copolymer (COC), using hot-embossing. A plasma enhanced chemical vapor deposition (PECVD) process with a tetraethyl orthosilicate (TEOS) precursor is then used locally to reduce the COC's wettability. The durability, degree, and localisation of the deposition are quantitatively assessed with scanning electron microscopy (SEM) coupled with energy-dispersive X-ray spectroscopy (EDS), IR spectroscopy, and contact angle measurements. Our fabrication method successfully produced mixed-wet micromodels with easily controllable wettability patterns. Additionally, our study also presents a qualitative analysis of the impact of wettability heterogeneities on multiphase flows for oil, water, and water-in-oil emulsion injections. The location of the treated surface areas is shown to strongly impact emulsion stability and transport.

Open-air plasma jets are becoming increasingly popular due to easy and affordable large-scale coating deposition on diverse substrates. However, direct deposition of primary amine groups (NH2), which are attractive as covalent anchor points for molecule grafting, remains challenging. In this study, 3-aminopropyltrimethoxysilane (APTMS) has been directly polymerized on glass by a plasma jet. Quantification of NH2 showed that APTMS polymerization and NH2 degradation were correlated with Yasuda's parameter and that a compromise between NH2 retention and coating stability is required. Evaporation of APTMS was found to improve surface smoothness and homogeneity but was found to decrease the deposited NH2 concentration, from 3.7 +/- 1.3 NH2/nm(2) to three times lower. Results showed that deposited NH2 could be used as anchor points for polyethylene glycol chain immobilization.

In biomaterials and biotechnology, coatings loaded with bioactive agents are used to trigger biological responses by acting as drug release platforms and modulating surface properties. In this work, direct deposition of poly(acrylic acid) coatings containing various agents, such as dyes, fluorescent molecules, was achieved by aerosol-assisted open-air plasma. Using an original precursors injection strategy, an acrylic acid aerosol was loaded with an aqueous aerosol and deposited on silicon wafers. Results clearly showed that agents dissolved in the aqueous aerosol were successfully entrapped in the final coating. The effect of aerosols concentration, flow rate, and treatment time, on the coating morphology and the amount of entrapped agents, was also investigated. It was demonstrated that this process has the potential to entrap a tunable amount of any sensible water-soluble agent without altering its activity. To the best of our knowledge, this is the first time that the loading of an aqueous aerosol in coatings deposited by plasma from a liquid aerosol precursor is reported. This innovative approach complements plasma deposition of coatings loaded with bioactive agents from aqueous aerosols with the use of non-volatile liquid precursors.

Although solid particles assembling on substrate surface is one of the key points for developing membrane reactors, the technology of organizing nano/near nanometer building blocks into complex structures is still a challenge to scientists in years. In this work, amine functional groups were deposited on the surface of different substrates via plasma enhanced chemical vapor deposition (PECVD) technology and (3-aminopropyl)triethoxysilane monomers were used as precursors. The influence of active gas, substrates, as well as deposition time on the physico-chemical features of as-deposited film were investigated, respectively. The highest density of amine of 5.5% on surface was obtained when Ar was utilized as active gas and deposition time was 40 s. Furthermore, Y type zeolite particles at near-nano size were synthesized and subsequently used as a model material for testing the immobilizing ability of plasma treated surface. The results clearly confirmed that a dense mono or multi-layer of closely packed zeolite particles could be formed on the APTES as-deposited surface after 24 h' immersion and the surface area of substrate could be improved by the deposition of zeolite.

The research on soft actuators including liquid crystal elastomers (LCEs) becomes more and more appealing at a time when the expansion of artificial systems is blooming. Among the various LCE actuators, the bending deformation is often in the origin of many actuation modes. Here, a new strategy with plasma technology is developed to prepare single-layer main-chain LCEs with thermally actuated bending and contraction deformations. Two distinct reactions, plasma polymerization and plasma-induced photopolymerization, are used to polymerize in one step the nematic monomer mixture aligned by magnetic field. The plasma polymerization forms cross-linked but disoriented structures at the surface of the LCE film, while the plasma-induced photopolymerization produces aligned LCE structure in the bulk. The actuation behaviors (bending and/or contraction) of LCE films can be adjusted by plasma power, reaction time, and sample thickness. Soft robots like crawling walker and flower mimic are built by LCE films with bending actuation.

The flow regime inside the channel of 3D printed microreactors is defined by the surface properties of the channel walls. Polylactide (PLA) and acrylonitrile/butadiene/styrene (ABS) are two polymers that are the most common in additive manufacturing using fused filament fabrication, commonly known as “3D printing”. With the aim of developing new materials for the 3D printing of microreactors whose channel surface hydrophobicity could be modified, PLA and ABS were blended with cheaper and widely used polymers-high-density polyethylene (PE-HD) and low-density polyethylene (PE-LD). Polymer blend surfaces were treated with inductively coupled plasma (ICP) and coated by fluorocarbon-based material (CFx) plasma deposition treatment in order to modify surface hydrophobicity. It has been shown that the modification of surface morphology of PLA polymer blends can be achieved by ICP etching and CFx coating, while this was not possible for ABS polymer blends under the conducted treatment conditions. The treated surface of PLA/PE-HD 90/10 showed a contact angle of 121.6° which is 36° higher than the contact angle measured on the untreated surface. Surfaces that have achieved contact angles higher than 120° have an “island like” surface morphology. Samples with higher “islands” showed higher contact angles, that confirmed that the hydrophobicity also depends on the height of the “islands”. Furthermore, it has been found that etching time significantly impacts the contact angle values and surface morphology of the PLA polymer blends, while the CFx coating time does not have significant impact on the surface properties.

The assembly of nano- and micro-scale building blocks on surface has been the focus of intense interest in materials science for years. In this work, (3-aminopropyl)triethoxysilane (APTES) carrying one primary amino group was deposited on various substrate surfaces using the plasma polymerization method. The key plasma parameters i.e. pressure and power were varied to obtained the highest density of primary amino groups. The influence of such parameters on the characteristics of deposited layers (e.g. chemical structure, adhesion strength, growth rate, etc.) was systemically investigated using various characterization methods such as XPS, FTIR, ellipsometry and so on. Meanwhile, three types of particles (AuNPs, zeolites and gold@zeolites) with sizes from nano- to submicro-range were synthesized and further used as model building blocks. Subsequently, the prepared particles were deposited onto cyclic olefin copolymer (COC) substrate surfaces, which were pre-functionalized by deposition of the plasma polymer layer using the parameters of pressure = 1.0 mbar and power = 30 W. The results confirmed the formation of membrane structures consisting of highly packed particles on the COC surface, and such immobilized structures showed high stability against flowing water, evidencing the good immobilization ability of deposited APTES layers with amino groups.

Lab-On-A-Chips promise solutions for high throughput and specific analysis for environmental and health applications, with the challenge to develop materials allowing fast, easy, and cheap microfabrication and efficient surface treatment. Cyclic olefin copolymer (COC) is a promising thermoplastic, easily microfabricated for both rapid prototyping and low-cost mass production of microfluidic devices but still needing efficient surface modification strategies. This study reports for the first time the optimization of an easy COC silica coating process by plasma-enhanced chemical vapor deposition at atmospheric pressure with plasma jet and tetraethylorthosilicate as precursor, leading to a 158 +/- 7 nm thickness and a 14-day-stability of hydrophilic properties for a COC-embedded microchannel (100 mu m), paving the way for a simplified and controlled COC surface modification. [GRAPHICS] .

In the present work, gold based catalysts were synthesized and immobilized on the surface of cyclic olefin copolymer (COC) microreactors. The microreactors were subsequently applied in a homemade microfluidic system for synthesizing benzaldehyde by oxidation of benzyl alcohol in water medium. The Au nanoparticles (NPs) immobilized on the inner surface of the microchannel showed a very high selectivity (94%) for benzaldehyde, while zeolite NPs exhibited only an adsorption feature to this reaction. Moreover, the results showed that the AuNP catalytic activity was maintained for at least 9 hours. However, the obtained conversion with AuNPs was only 20%, indicating a relatively low productivity. In comparison, AuNPs assembled on the surface of zeolite NPs (AuNPs@zeolite) and immobilized in the microchannel showed the best catalytic performance, as the highest benzaldehyde selectivity (>99%) with a relatively high benzyl alcohol conversion of 42.4% was achieved under the same conditions. To the best of our knowledge, this is the first example demonstrating the use of AuNP or AuNP@zeolite catalysts in a microsystem performing such high selectivity for benzaldehyde in water medium.

Immobilization of gold nanoparticles (AuNPs) on the surface of zeolite has received a great interest due to Au@zeolite’s unique characteristics and high performance for catalysis. In this work we studied the grafting of two different functional molecules; one having an amine group (3-aminopropyl)triethoxysilane (APTES) and the second having a thiol group (3-mercaptopropyl)trimethoxysilane (MPTES) on the surface of zeolite using the same wet chemistry method. The modified zeolite surfaces were characterized using zeta potential measurements; diffuse reflectance infrared fourier transform (DRIFT) and X-ray photoelectron spectroscopy (XPS). The results confirmed a successful deposition of both functional groups at the topmost surface of the zeolite. Furthermore; transmission electron microscopy (TEM), ultraviolet-visible (UV-Vis) spectroscopy and XPS results clearly evidenced that APTES provided a better AuNPs immobilization than MPTES as a result of; (1) less active functions obtained after MPTES deposition, and (2) the better attaching ability of thiol to the gold surface.

Immobilization of colloidal particles (e.g. gold nanoparticles (AuNps)) on the inner surface of micro-/nano-channels has received a great interest for catalysis. A novel catalytic ozonation setup using a gold-immobilized microchannel reactor was developed in this work. To anchor AuNps, (3-aminopropyl) triethoxysilane (APTES) with functional amine groups was deposited using plasma enhanced chemical vapor deposition (PECVD) process. The results clearly evidenced that PECVD processing exhibited relatively high efficiency for grafting amine groups and further immobilizing AuNPs. The catalytic activity of gold immobilized microchannel was evaluated by pyruvic acid ozonation. The decomposition rate calculated from High Performance Liquid Chromatography (HPLC) indicated a much better catalytic performance of gold in microchannel than that in batch. The results confirmed immobilizing gold nanoparticles on plasma deposited APTES for preparing catalytic microreactors is promising for the wastewater treatment in the future. (C) 2018 Elsevier B.V. All rights reserved.

A novel biphasic gas/liquid plasma microreactor performed controlled oxidation of cyclohexane into “KA oil” with more than 70% selectivity and more than 10% conversion.

In this paper, a novel plasma/liquid microreactor has been developed to generate and inject radical species with the aim to perform chemical synthesis reactions in liquid phase. Plasma has always been considered as a source of reactive species, such as radicals, atoms, electrons, etc., with applications mostly dedicated to surface modifications of materials. By injecting reactive species created by the plasma to the liquid phase, it is possible to initiate liquid phase synthesis reactions. In addition, gas/liquid interactions can be enhanced with a high surface-area-to-volume ratio by confining the plasma and the liquid in diphasic micro-structured systems. Herein is reported a novel plasma/liquid microreactor for liquid phase radical reactions. Radicals are generated in the gas phase in a steady flow microreactor and then transported to the liquid phase. The spin trapping reaction and the electron paramagnetic resonance (EPR) spectroscopy have been used to identify and quantify the radical species generated in the microreactor. Hydroxyl radicals and hydrogen atoms have been detected and measured in the liquid phase, indicating the huge potential of the microreactor as a handful tool for chemical synthesis.

Treatment of household wastewater loaded with hair colorants by means of solar photocatalysis using TiO2-coated polyester/wool textile has been reported recently. In this work, the attributes of immobilized photocatalyst were enhanced; a textile support (polyester/wool blend fabric) was pre-treated by atmospheric and low pressure oxygen plasma prior to coating of the surface. Plasma pre-treatment contributed to hydrophilisation of support and overall resistance to wear of immobilized photocatalyst was improved. Moreover, TiO2-chitosan composite coating was modified by the addition of triarylmethane dye (CI. Basic Blue 1; BB1). The sensitizing effect of the dye was observed during the first 180 min of photocatalytic treatment of greywater polluted by hair colorants under solar irradiation. Adversarially, the rate of photocatalytic degradation of bisphenol A (BPA) model solution under visible light was lower in the presence of BBI in the photocatalyst formulation. According to the performed study of BB1 chemistry in aqueous solution, it was found that the dye undergoes two distinct photodegradation mechanisms depending on the characteristics of studied system. When dominant, photoreduction of BB1 to leuco-fOrm (BBI-H), provides additional electron capture and consequently ensures decrease in h(+)- e(-) recombination rates, resulting in a false sensitizing effect. (C) 2017 Elsevier B.V. All rights reserved.

Polymers among new classes of materials such as polydimethylsiloxane (PDMS), cyclic olefin copolymer (COC), Norland optical adhesive (NOA), and THV (fluoropolymer) were evaluated as surface-modified microfluidic materials, including investigating the incorporation of silica-like functional groups onto these surfaces. The functionalization of these materials was performed using a hybrid reactor equipped with magnetron sputtering using a silica target and with a PECVD apparatus starting from hexamethyldisiloxane as a chemical precursor. Coated microfluidic materials were then evaluated in terms of wettability, stability, composition, and structure. The deposited coatings were proved to be stable up to 2 month in air and water storage for these materials, with COC providing the most stable substrate.

This paper describes a novel gliding Arc discharge reactor producing a non-thermal plasma at atmospheric pressure in humid air. The ionized gas is generated in a spray-tower absorber for the treatment of organic pollutants. The reactor configuration enables the plasma-degradation of micro-droplets effluents in the spatial post-discharge mode. This type of design allows to exclude the direct contact between the plasma plume and the liquid to be treated in order to avoid the liquid heating and the flame extinction problems. A hydrodynamic study coupling 'Navier-Stokes' equations and those of 'Convection-Diffusion' allowed to calculate the concentration profiles and the droplet falling velocity. The stripping of phenol was studied to valid the hydrodynamic approach. Experiences and simulations showed that after 1h of treatment, only 5% of the compound was transferred into the plasma phase. The spatiality of the novel reactor allowed a degradation rate of 100% for catechol after 38min of plasma-treatment. For 4-nitrophenol, the degradation rate reached 90% after 120min. Phenol and its by-products degradation were totally degraded by combining the spatiality of the reactor and the temporal post-discharge. A degradation mechanism was proposed and a plasmachemical reaction in relation with the pernitrous acid species was confirmed.

A novel method for designing hydrophobicity of the polylactide/low-density polyethylene (PLA/PE-LD) blends by creating specific surface topography is proposed. In order to increase hydrophobicity by changing the topography of two-phase PLA polymer blend surface, blends are etched by using ICP before the fluorocarbon-based coating treatment done in the second step. During the surface treatment process PLA is etched significantly more than PE-LD and specific “island-like” surface morphology is created. It has small pillars, 15 µm wide and approximately 125 µm away from each other, which after the fluorocarbon-based treatment has very high contact angle (>120°). Without the etching, due to smooth surface, PLA/PE-LD 90/10 polymer blend contact angle is between 100° and 110°.