Personne : Laroche, Gaétan
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Université Laval. Département de génie des mines, de la métallurgie et des matériaux
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- PublicationAccès libreAtmospheric pressure cold plasma versus wet-chemical surface treatments for carboxyl functionalization of polylactic acid : a first step toward the immobilization of bioactive molecules(Elsevier, 2020-02-08) Laroche, Gaétan; Rodríguez Durán, Iván; Vanslambrouck, Stéphanie; Chevallier, PascaleThe use of polylactic acid (PLA) has attracted growing interest, particularly in recent years, for biomedical applications because of its mechanical properties, biocompatibility, and biodegradability. Despite this, features such as surface hydrophobicity and the absence of suitable functional groups for covalent immobilization of bioactive molecules, make it challenging to endow PLA-based medical devices with additional features and thus broaden their range of applicability. In the present study, we demonstrate the suitability of atmospheric pressure dielectric barrier discharges operating in the Townsend regime as a promising alternative to other surface treatments, such as diazonium and alkali hydrolytic treatments, for carboxyl functionalization of PLA. Chemical changes in PLA surfaces are evaluated by contact angle measurements and by X-ray photoelectron spectroscopy while physical changes are investigated by scanning electron microscopy and atomic force microscopy. The amount of carboxyl groups generated on PLA surfaces is assessed by toluidine blue O assay and substantiated by grafting, through carboxyl groups, a fluorescent probe containing amino functionalities. All of the surface treatments have proven to be very effective in generating carboxylic groups on the PLA surface. Nevertheless, plasma treatment is shown to not degrade the PLA surface, in sharp contrast with diazonium and alkali hydrolytic treatments.
- PublicationAccès libreCharacterization of argon dielectric barrier discharges applied to ethyl lactate plasma polymerization(Institute of Physics Publishing Ltd, 2017-11-03) Laroche, Gaétan; Desjardins, Edouard; Naudé, Nicolas; Meichelboeck, Maximilian; Laurent, Morgane; Stafford, Luc; Gherardi, NicolasThe influence of the input voltage frequency (35 and 150 kHz), interelectrode gap (1 and 2 mm) and precursor concentration (250, 350, and 450 ppm) on the electron temperature (Te), number density of metastable Ar atoms (n(Arm)), and discharge current density (proportional to the electron density ne) is studied in an argon-ethyl lactate dielectric barrier discharge (DBD). An argon-ammonia Penning mixture is also considered as reference. These results are correlated to the chemistry (XPS, IR) and topography (AFM) of the ethyl-lactate-based plasma polymer coatings. Low Te values from 0.3 to 0.5 eV were obtained for all discharges. This observation, in addition to resemblances with the Ar–NH3 mixture, suggested that the ionization kinetics of ethyl lactate-based discharges is driven by Penning reactions. Among the investigated parameters, the dissipated power obtained through changes of the excitation frequency had the largest impact on both the coatings properties and the discharge behavior.
- PublicationAccès libreElectrode cleanliness impact on the surface treatment of fluoropolymer films for a long-lasting plasma process(Elsevier, 2020-09-16) Gélinas, Alex; Laroche, Gaétan; Laurent, MorganeA dielectric barrier discharge in a continuous process configuration is used to coat the surface of polymer films. The effect of the growth of a coating layer on top of the uncovered electrode with regards to the physicochemical properties of the film treatment is studied. Plasma electrical parameters such as power density (W.cm−2) and voltage (kV) are monitored during a typical cycle, which is comprised between two electrode cleanings. In addition, the surface energy and chemistry are determined at chosen time-points of the process by contact angle measurements with two liquids and X-ray photoelectron spectroscopy (XPS). Based on these analyses, no major modification of the coated polymer physicochemical properties was attributed to the deposition of an organic layer on top of the bare electrodes after the equivalent of 1 h of continuous treatment.
- PublicationAccès libreFourier-Transform infrared spectroscopy of ethyl lactate decomposition and thin-film coating in a filamentary and a glow dielectric barrier discharge(Wiley-VCH-Verl., 2021-07-05) Milaniak, Natalia; Laroche, Gaétan; Massines, FrançoiseGlow and filamentary regimes of atmospheric pressure plasma-enhanced chemical vapor deposition in a planar dielectric barrier discharge configuration were compared for thin-film deposition from ethyl lactate (EL). EL decomposition in the plasma phase and thin-film composition were both characterized by Fourier- transform infrared spectroscopy. EL chemical bonds' concentration along the gas flow decreases progressively in the glow dielectric barrier discharge (GDBD), whereas it drastically oscillates in the filamentary dielectric barrier discharge (FDBD), with values higher than that of the initial mixture. EL decomposition route depends on the discharge regime, as the decrease of the concentration of the different investigated bonds is different for an identical amount of energy provided to EL molecules. CO2 is systematically formed reaching concentrations of 25 and 40 ppm, respectively, in FDBD and GDBD.
- PublicationRestreintAtmospheric-pressure plasma-enhanced chemical vapor deposition of nanocomposite thin films from ethyl lactate and silica nanoparticles(Weinheim Wiley-VCH-Verl., 2020-10-09) Milaniak, Natalia; Laroche, Gaétan; Massines, FrançoiseNanocomposite coatings are made by atmospheric-pressure plasma-enhanced chemical vapor deposition from ethyl lactate (EL) and silica nanoparticles (NPs) in a dielectric barrier discharge (DBD) using frequency-shift keying (FSK) to alternate between 1- and 15-kHz voltages. In situ plasma Fourier-transform infrared spectroscopy (FTIR) and thin film FTIR, scanning electron microscopy, atomic force microscopy, and profilometry show that (i) 1 kHz DBD mainly deposits NPs, 15 kHz only polymerizes EL; (ii) the EL polymerization rate is the same in FSK and continuous modes; (iii) despite the 50/50 contribution of both frequencies, the NP deposit is three times faster in FSK mode than in 1 kHz DBD and compared with 1 and 15 kHz coatings, in the nanocomposite, NP Si–O–Si and EL C═O bonds per unit length are equal to 68% and 34%, respectively. In situ FTIR detects SiO2 NPs, their functionalization, and the formation of CO2.
- PublicationAccès libreInterpretation of artifacts in Fourier transform infrared spectra of atmospheric pressure dielectric barrier discharges : relationship with the plasma frequency between 300 Hz and 15 kHz(Institute of physics, 2019-10-11) Milaniak, Natalia; Audet, Pierre; Laroche, Gaétan; Griffiths, Peter R.; Massines, FrançoiseThis article describes the occurrence of a phenomenon that is observed while recording mid-infrared (4000–700 cm−1) absorption spectra of dielectric barrier discharges sustained at frequencies ranging from 300 Hz to 15 kHz. This phenomenon is observed as the presence of very sharp spikes in the spectrum, for which the wavenumber depends on both the high voltage frequency used to generate the discharge and the velocity of the moving mirror of the interferometer (which in turn determines the interferogram sampling frequency). While it is well known that the consumption of gas precursor within plasmas can be followed, we demonstrate that Fourier transform infrared spectroscopy also makes it possible to monitor frequencies and coupling of excitation mechanisms occurring in the plasma.