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 libreUnveiling the origin of the anti fogging of plasma-coated glass : role of the structure and chemistry of siloxane precursors(Elsevier Science, 2020-01-25) Laroche, Gaétan; Rodríguez Durán, IvánThe application of (super)hydrophilic coatings in sectors of activity concerned by fogging, such as the food industry, the architectural sector, and medicine has attracted enormous attention over the past few years. However, despite this interest, most of the coating deposition techniques used thus far are not suitable for large-scale production because of their multistep nature. In this regard, the use of atmospheric pressure dielectric barrier discharges (AP-DBD) operated under a controlled N2/N2O atmosphere offers a promising alternative to conventional deposition techniques for the fabrication of anti-fogging coatings. Using this one-step coating approach, four siloxane precursors with different structures and different number of Si―H and Si−CH3 groups; namely, 1,3,5,7-tetramethylcyclotetrasiloxane (TMCTS), octamethylcyclotetrasiloxane (OMCTS), 1,1,3,3-tetramethyldisiloxane (TMDSO), and hexamethyldisiloxane (HMDSO) were deposited on glass samples. Because of their extreme wetting behavior (WCA < 5°), TMCTS-coated glasses featured an excellent anti-fogging performance, in contrast to OMCTS-, TMDSO-, and HMDSO-coated glasses which were not fogging-resistant (WCA ≈ 80°)). Coupled with hydrophilic functionalities, such as Csingle bondO, Odouble bond Csingle bondO, and Sisingle bondOH groups, the relatively high surface roughness of TMCTS-coated glass, compared with that of OMCTS-, TMDSO-, or HMDSO-coated glass, accounted for its superior visual characteristics when exposed to water vapor at 80 °C. These results allow us to confidently conclude that the cyclic structure of TMCTS in conjunction with the high reactivity of the Si-H bonds is responsible for the observed anti-fogging effect.
- PublicationAccès libreWater drop-surface interactions as the basis for the design of anti-fogging surfaces : theory, practice, and applications trends(Elsevier Science, 2018-11-24) Laroche, Gaétan; Rodríguez Durán, IvánGlass- and polymer-based materials have become essential in the fabrication of a multitude of elements, including eyeglasses, automobile windshields, bathroom mirrors, greenhouses, and food packages, which unfortunately mist up under typical operating conditions. Far from being an innocuous phenomenon, the formation of minute water drops on the surface is detrimental to their optical properties (e.g., light-transmitting capability) and, in many cases, results in esthetical, hygienic, and safety concerns. In this context, it is therefore not surprising that research in the field of fog-resistant surfaces is gaining in popularity, particularly in recent years, in view of the growing number of studies focusing on this topic. This review addresses the most relevant advances released thus far on anti-fogging surfaces, with a particular focus on coating deposition, surface micro/nanostructuring, and surface functionalization. A brief explanation of how surfaces fog up and the main issues of interest linked to fogging phenomenon, including common problems, anti-fogging strategies, and wetting states are first presented. Anti-fogging mechanisms are then discussed in terms of the morphology of water drops, continuing with a description of the main fabrication techniques toward anti-fogging property. This review concludes with the current and the future perspectives on the utility of anti-fogging surfaces for several applications and some remaining challenges in this field.
- PublicationAccès libreCurrent trends, challenges, and perspectives of anti-fogging technology : surface and material design, fabrication strategies, and beyond(Pergamon Press, 2018-09-07) Laroche, Gaétan; Rodríguez Durán, IvánTransparent materials such as glasses and some polymers play an essential role in our daily life. Indeed, it is well known that their application in mirrors, windows, automobile windshields, and eyewear make our day-to-day activities more comfortable. These examples aside, many more can also be found in several spheres of human activity, including such sectors as diverse and distinct as the medical, photovoltaic and food industry fields. Unfortunately, due to the unavoidable condensation of water vapor on solid surfaces, these materials undergo fogging under normal operating conditions. More than a mere nuisance, this naturally occurring phenomenon adversely affects their optical performance as it lowers the light-transmitting capability and often gives rise to esthetical, hygienic, and safety concerns. In this context, research in the field of anti-fogging technology has attracted growing interest, particularly in recent years, for numerous potential applications. In this review, recent developments in the design and manufacturing of anti-fogging surfaces are described in detail, beginning with the fogging mechanism in terms of nucleation and growth of water drops. Anti-fogging strategies explored thus far and mainly focusing on hydrophilic and hydrophobic surfaces are then extensively described. Finally, based on current research in this promising field, future trends and prospects for their effective implementation are presented.
- PublicationAccès libreResponse surface methodology as a predictive tool for the fabrication of coatings with optimal anti-fogging performance(Lausanne Elsevier Sequoia, 2020-12-15) Laroche, Gaétan; Profili, Jacopo; Rodríguez Durán, Iván; Stafford, LucIn this study, response surface methodology was applied to optimize the anti-fogging performance of coatings deposited on commercial glass samples from 1,3,5,7-tetramethylcyclotetrasiloxane (TMCTS)/N2O mixtures by atmospheric pressure plasma enhanced chemical vapor deposition. The effect of the dissipated power (DP), [N2O]/[TMCTS] ratio, and sample scroll speed on the anti-fogging performance was investigated by means of a Box-Behnken experimental design. The regression model relating transmittance of the coated glasses to these deposition parameters revealed that the anti-fogging performance strongly depends on the second-order interaction of the dissipated power and [N2O]/[TMCTS] ratio (i.e., DP × [N2O]/[TMCTS]). Contour plots showed that the dissipated power required to prepare optimal anti-fogging coatings should be of at least 0,7, 0,5 or 0,4 W cm−2, if the [N2O]/[TMCTS] ratio in the plasma is 20, 30, or 40, respectively. When placed over water at 50°C, the coated glass samples allowed 80% (or more) of 590-nm light to pass through, thus meeting the minimal anti-fogging requirement for alpine skier goggles and faceshields. Despite not having a significant impact on the anti-fogging performance, the sample scroll speed is key to fabricating coatings with the desired thickness during in-line manufacturing.
- PublicationAccès libreAtmospheric pressure townsend discharges as a promising tool for the one‐step deposition of antifogging coatings from N2O/TMCTS mixtures(Wiley, 2020-02-13) Laroche, Gaétan; Durocher-Jean, Antoine; Rodríguez Durán, Iván; Profili, Jacopo; Stafford, LucThe need to ensuring the “see‐through” property of transparent materials when exposed to sudden temperature changes or very humid conditions has encouraged the development of antifogging strategies, such as the deposition of (super)hydrophilic coatings. However, despite the effectiveness of these coatings in combating the effects of fogging, most of the coating techniques explored to date are typically time‐consuming and environment‐unfriendly. Bearing this in mind, we demonstrate that the application of dielectric barrier discharges operated at atmospheric pressure proves to be successful in preparing antifogging coatings on glass samples from 1,3,5,7‐tetramethylcyclotetrasiloxane (TMCTS) and nitrous oxide (N2O). The antifogging performance of the coatings was found to be governed by the [N2O]/[TMCTS] ratio and not by the [N2O] + [TMCTS] sum. Coatings prepared under a [N2O]/[TMCTS] = 30 were superhydrophilic (water contact angles ≈ 5°–10°) due to surface silanol groups and endowed glass samples with a superior antifogging property, as revealed by the ASTM F 659‐06 test. In contrast, because of the lesser hydrophilicity (water contact angles ≈ 60°), coatings prepared under a [N2O]/[TMCTS] = 10 did not endow glass samples with antifogging property. Regardless of the deposition conditions, the plasma‐deposited coatings displayed crack‐free smooth surfaces (Rrms = 2−4 nm).
- PublicationAccès libreDeposition of anti-fog coatings on glass substrates using the jet of an open-to-air microwave argon plasma at atmospheric pressure(Wiley-VCH-Verl., 2020-04-22) Durocher-Jean, Antoine; Rodríguez Durán, Iván; Asadollahi, Siavash; Laroche, Gaétan; Stafford, LucThis study reports a one-step process for the formation of anti-fog coatings on commercial glass substrates using the jet of an open-to-air microwave argon plasma at atmospheric pressure with hexamethyldisiloxane (HMDSO) as the precursor for plasma-enhanced chemical vapor deposition. Optical microscopy and broadband light transmittance measurements revealed significant precursor fragmentation and gas phase association reactions when HMDSO was injected close to the tube outlet, resulting in powder-like, hydrophobic, and semiopaque glass surfaces. On the contrary, injection of HMDSO close to the substrate led to smoother, homogeneous, hydrophilic, and transparent glass surfaces. In addition, transmittance measurements at 590 nm in humid air according to American Society for Testing and Materials standard tests revealed superior antifogging properties to plasma-treated glass substrates. On the basis of the optical emission and absorption spectroscopy measurements, electrons, metastable argon atoms, and hot neutral argon atoms were mostly responsible for the significant precursor fragmentation close to the tube outlet, whereas the contribution of hot neutrals and ultraviolet photons became important close to the substrate.
- PublicationRestreintBeyond microelectronics with 1,3,5,7-tetramethylcyclotetrasiloxane : a promising molecule for anti-fogging coatings(Elsevier Sequoia, 2019-12-04) Laroche, Gaétan; Profili, Jacopo; Rodríguez Durán, Iván; Stafford, LucOver the past few years, a growing number of studies have focused on designing coatings for use in applications dealing with the fogging phenomenon such as endoscopes, automobile side view mirrors, and protective goggles. However, because of the long manufacturing times, the implementation on an industrial scale of most of the coating techniques used thus far is still a pending issue. Bearing this in mind, we report on the use of atmospheric pressure dielectric barrier discharges (AP-DBDs) operated in the presence of nitrous oxide (N2O) and 1,3,5,7-tetramethylcyclotetrasiloxane (TMCTS), as a reliable coating strategy for the one-step fabrication of anti-fogging glass. An increase in either the [N2O]/[TMCTS] ratio or the dissipated power resulted in coatings with such hydrophilic groups on the surface as Si–OH, C–O, and OC–O; and a structure similar to that of SiO2. Because of their “water-loving” characteristics (WCA < 40°), coatings deposited under a [N2O]/[TMCTS] ratio ≥ 30 and a dissipated power ≥ 0.25 W cm−2 conferred a remarkable anti-fogging performance to glass samples when placed over water at 80 °C. After 30 s of exposure to water vapor at 50 °C (ASTM F 659-06), the coated glasses exhibited a light transmittance greater than that of the uncoated glass (90% vs. 55%). These results illustrate how by controlling the dissipated power and the [N2O]/[TMCTS] ratio in the plasma anti-fogging glass can readily be fabricated.