Personne :
Laroche, Gaétan

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Université Laval. Département de génie des mines, de la métallurgie et des matériaux
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Voici les éléments 1 - 6 sur 6
  • Publication
    Accès libre
    Water 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, Iván
    Glass- 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.
  • Publication
    Accès libre
    Optical emission spectroscopy as a process-monitoring tool in plasma enhanced chemical vapor deposition of amorphous carbon coatings - multivariate statistical modelling
    (Elsevier Science, 2018-03-01) Turgeon, Stéphane; Anooshehpour, Farid; Laroche, Gaétan; Mantovani, D.; Cloutier, Maxime
    Production of Diamond-Like Carbon (DLC) nanocoatings using plasma enhanced chemical vapor deposition is studied by Optical Emission Spectroscopy (OES) as a plasma diagnostic technique. The objective of the current research is to establish a predictive model of DLC properties using a multivariate analysis method. This model is based on OES data instead of process parameters, which are reactor dependent and accordingly, their effect on the plasma deposition process may vary from one reactor to another. The predictive potential of OES is evaluated using partial least square regression (PLSR) analysis. The results show that OES derived data are capable of replacing some process parameters to predict the DLC properties. The perspective of PLSR modelling and OES application for the development and monitoring of a structurally graded DLC coating is also discussed.
  • Publication
    Accès libre
    Current 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, Iván
    Transparent 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.
  • Publication
    Accès libre
    Single or mixed tethered peptides to promote hMSC differentiation toward osteoblastic lineage
    (American Chemical Society, 2018-11-27) Padiolleau, Laurence; Chanseau, Christel; Laroche, Gaétan; Durrieu, Stephanie; Chevallier, Pascale; Durrieu, Marie-Christine
    The commitment and differentiation of human mesenchymal stem cells (hMSCs) are guided by bioactive molecules within the extracellular matrix. Among the various approaches to design biomaterials, the functionalization of biomaterial surfaces with peptides from the sequence of proteins from the extracellular matrix is quite common. The purpose of this functionalization is to recruit hMSCs and promote their differentiation into the appropriate lineage. The aim of this work was to investigate the influence of RGD and FHRRIKA peptides and peptide sequences taken from bone morphogenic protein (BMP-2) and histone H4 (osteogenic growth peptide; OGP) either tethered alone or as a mixture on the surface of a model material and to also examine the level of hMSC osteogenic commitment without using a differentiation medium. Grafting of the different peptides was assessed by X-ray photoelectron spectroscopy (XPS), while their surface density was quantified by fluorescence microscopy, and their surface properties were assessed by atomic force microscopy (AFM) and contact angle (CA). The osteogenic commitment of hMSCs cultured on the different surfaces was characterized by immunohistochemistry using Runx-2 as an earlier osteogenic marker and OPN, a late osteogenic marker, and by RT-qPCR through the expression of ColI-a1, Runx-2, and ALP. Biological results show that the osteogenic commitment of the hMSCs was increased on surfaces tethered with a mixture of peptides. Results indicate that tethered peptides in the range of pmol mm–2 were indeed effective in inducing a cellular response after 2 weeks of cell culture without using an osteogenic media. These findings contribute to the research efforts to design biomimetic materials able to induce a response in human stem cells through tethered bioactive molecules for bone tissue engineering.
  • Publication
    Accès libre
    Correlation between the plasma characteristics and the surface ‎chemistry of plasma-treated polymers through partial least ‎squares analysis
    (ACS Publications, 2013-12-06) Turgeon, Stéphane; Duchesne, Carl; Ghasemzadeh-Barvarz, Massoud; Laroche, Gaétan; Mavadat, Maryam
    We investigated the effect of various plasma parameters (relative density of atomic N and H, plasma temperature, and vibrational temperature) and process conditions (pressure and H2/(N2 + H2) ratio) on the chemical composition of modified poly(tetrafluoroethylene) (PTFE). The plasma parameters were measured by means of near-infrared (NIR) and UV-visible emission spectroscopy with and without actinometry. The process conditions of the N2-H2 microwave discharges were set at various pressures ranging from 100 to 2000 mTorr and H2/(N2+H2) gas mixture ratios between 0 and 0.4. The surface chemical composition of the modified polymers was determined by X-ray photoelectron spectroscopy (XPS). A mathematical model was constructed using the partial least-squares regression algorithm to correlate the plasma information (process condition and plasma parameters as determined by emission spectroscopy) with the modified surface characteristics. To construct the model, a set of data input variables containing process conditions and plasma parameters were generated, as well as a response matrix containing the surface composition of the polymer. This model was used to predict the composition of PTFE surfaces subjected to N2-H2 plasma treatment. Contrary to what is generally accepted in the literature, the present data demonstrate that hydrogen is not directly involved in the defluorination of the surface but rather produces atomic nitrogen and/or NH radicals that are shown to be at the origin of fluorine atom removal from the polymer surface. The results show that process conditions alone do not suffice in predicting the surface chemical composition and that the plasma characteristics, which cannot be easily correlated with these conditions, should be considered. Process optimization and control would benefit from plasma diagnostics, particularly infrared emission spectroscopy.
  • Publication
    Accès libre
    Partial least squares regression as a tool to predict fluoropolymer surface modification by dielectric barrier discharge in a corona process configuration in a nitrogen-organic gaseous precursor environment
    (American Chemical Society, 2018-05-16) Turgeon, Stéphane; Laroche, Gaétan; Vallade, Julien
    A dielectric barrier discharge in a corona process configuration is used to treat the surface of fluoropolymers in a nitrogen–organic precursor environment. The surface chemistry, thickness, and water contact angle of the deposited coatings are measured and used to build up an output matrix to be correlated with an input matrix built using electrical parameters of the discharge, the gas mixture chemical composition, and spectroscopic parameters measured in both the infrared and ultraviolet–visible emission spectral regions. A partial least-squares regression (PLSR) model enables determining the most important plasma parameters to drive the coating physicochemical characteristics. From the PLSR model, it is determined that the plasma electrical parameters drive the surface modification process, at the expense of other plasma characteristics such as gas flow, gaseous precursor concentration, nitrogen vibrational temperature, and the level of gaseous precursor conversion within the plasma.