30 November 2019 - Materials, Mechanical, Civil Engineering, Electrochemistry Ph.D. title
Smart dressings: grafting of active molecules on biocompatible materials. Supervision Julien BRAS, Associate Professor HDR, Grenoble INP-Pagora / LGP2 ♦♦ Bruno JEAN, Researcher, Cermav ♦♦ Guillaume NONGLATON, Engineer Researcher, CEA-Leti Abstract
In a context where the need for innovative medical devices is increasing and the environmental issue is becoming a major concern, the objective of the project the aim of the project was to prepare antimicrobial wound dressings using the greenest possible way. For this purpose, nanocelluloses have been chosen as bio-based and biocompatible building blocks for the design of porous architectures and their functionalization with antimicrobial agents was then undertaken in supercritical CO2 medium (CO2sc) used as an alternative to organic solvents and by taking advantage of its specificities such as high diffusivity, easy removal of solvent and residual reagents and compatibility with fragile materials. Thus, 2D and 3D structures, nanopapers, cryogels and aerogels, were prepared from cellulose nanofibrils (CNF) and nanocrystals (CNC), and exhibited various properties in terms of morphology, porosity and specific surface area. In order to introduce antibacterial functionality, cryogels prepared from nanocellulose with varied surface chemistries were impregnated in CO2sc with a synthetic antibiotic, ciprofloxacin. Impregnated cryogels exhibited antibacterial activity against both gram-negative and gram-positive bacterial strains. Then, four materials of increasing specific surface area, all prepared from CNF, were impregnated with an essential oil molecule, thymol. Results show a direct relationship between of the amount of impregnated molecules and the specific surface that leads in the case of cryo- and aerogels to good antimicrobial properties against two types of bacteria and yeast. In a second strategy, covalent grafting of CNF structures in supercritical CO2 was investigated with a novel antibacterial aminosilane. Surface analysis characterizations methods (X-ray photoelectron spectroscopy, contact angle and surface zeta potential analysis) confirmed the successful grafting on nanopapers. The contact active properties of grafted nanopapers and cryogels were assessed. These results are very promising for the design of antimicrobial bio-based and biocompatible medical devices using supercritical conditions. Other members of the jury
1st July 2019 - Fluid Mechanics, Energy, Processes Ph.D. title
Study of depolymerization processes of oligosaccharides from hemicelluloses in a biorefinery. Supervision Christine CHIRAT, Professor, Grenoble INP-Pagora / LGP2 ♦♦ Dominique LACHENAL, Emeritus Professor, Grenoble INP-Pagora / LGP2 Abstract
The lignocellulosic biomass is composed of 30% hemicelluloses, which are small polysaccharides. They can lead to interesting chemical platforms that can be declined in various products arousing a growing interest.
In a wood based biorefinery, hemicelluloses were solubilized by water pre-hydrolysis under the form of monosaccharides and oligosaccharides. Then, secondary hydrolysis were performed to convert those oligosaccharides to monosaccharides (acid hydrolysis) or xylans to xyloses (enzymatic hydrolysis). Other members of the jury
Ana Paula DUARTE, Professor, Universidade da Beira Interior, Portugal ♦♦ Nicolas BROSSE, Professor, Université de Lorraine ♦♦ Pierre-Yves PONTALIER, Associate Professor, Toulouse INP-ENSIACET
21 June 2019 - Fluid Mechanics, Energy, Processes[Online thesis] Ph.D. title
Measurement, analysis and modeling at the microscale of printed dots to improve the printed anti-counterfeiting solutions. Supervision Nadège REVERDY-BRUAS, Associate Professor HDR, Grenoble INP-Pagora / LGP2 ♦♦ Lionel CHAGAS, Research Engineer, Grenoble INP-Pagora / LGP2 Abstract
Applications in the field of product security and authentication to prevent counterfeiting rely on abilities of microscale measurements of printed dots. Thus, researches described in this manuscript have been directed toward the development of measurement methods and apparatus to characterize halftone dot at the microscale.
A polarized reflection optical microscope has been adapted with a commercial digital camera. The Bayer matrix was removed from the surface of the camera and raw images were retrieved. The microscope stage, the camera, the photometer and the thermometer were controlled directly in a Python graphic user interface specifically developed. A high dynamic range capture method was proposed and tuned specifically to obtain richer information on the ink and paper regions. The measurement apparatus and methods helped improve the accuracy and automate the measurements of the halftone dots at the microscale.
The physical and optical dot gains were then separated and analyzed. A Gaussian fitting of the ink and paper histogram peaks was proposed to measure automatically the ink and paper region reflectance as a function of the ink coverage. Thresholding algorithms were applied to separate optical and physical dot gain. An objective threshold evaluation method was developed in order to define the best threshold algorithms for halftone images. The method was based on a simulation of the optical dot gain effects and of the microscope distortions to obtain test images and ground truth images.
Thirty threshold algorithms from literature were evaluated and demonstrated dependency on the ink coverage of the halftones. Two novel threshold algorithms were then developed specifically to process halftones. The first threshold algorithm was based on the determination of the amount of ink peak shift. The second threshold algorithm proposed a pretreatment of the images by applying a pseudo-deconvolution strategy, removing the optical dot gain from the halftones. Characterizations of the optical and physical dot gains were then conducted analyzing 2708 different halftones.
Finally, a physical dot gain model and an optical dot gain model were proposed in order to predict the halftone reflectances from raster to print. The physical dot gain model was based on the generation of single ink particles placed according to a probability mask and on a fusion of the ink particles. The model was evaluated with 43269 dot morphologies that were captured automatically on the microscope. A novel halftone reflectance model was proposed based on a double convolution with two different paper point spread functions. It allowed an accurate reproduction of the main effects of the light diffusion with, at the same time, an accurate reproduction of the light entrapment near the edges of the dots. Other members of the jury
Mathieu HÉBERT, Associate Professor, Université Jean Monnet Saint-Étienne ♦♦ Patrick BAS, Research Director, Centrale Lille ♦♦ Edgar DÖRSAM, Professor, Technische Universität Darmstadt, Germany ♦♦ Naceur BELGACEM, Professor, Grenoble INP-Pagora / LGP2
27 May 2019 - Fluid Mechanics, Energy, Processes Ph.D. title
Concepts and developments for the production of bleached, pure or oxidized cellulosic pulp from recycled lignocellulosic material. Supervision Gérard MORTHA, Professor, Grenoble INP-Pagora / LGP2 ♦♦ Nathalie MARLIN, Associate Professor, Grenoble INP-Pagora / LGP2 Abstract
Today recovered papers and boards are recycled into similar products; in particular old corrugated boards are transformed into new corrugated boxes. Rich in lignocellulosic material, recovered carton boards might replace wood for the production of higher added-value products. The thesis work investigated the potential of existing processes for delignification, bleaching and cellulose purification, applied on fiber mixes simulating the composition of various carton boards, for the production of bleached paper pulp and dissolving pulp grades.
The treatment was composed of a Kraft cook, followed by a conventional D0-Ep-D1 bleaching sequence, and in the case of dissolving pulp production, a CCE stage for cellulose purification was added. Because carton boards exhibit various fiber compositions, all the study has been conducted on model mixes, made of fibers from unbleached Kraft pulp and mechanical pulp. In all cases, fully bleached pulps have been successfully obtained, although pulp viscosity was sometimes below the standards. Moreover bleached pulps were found difficult to purify. Overall, it has been shown that the quality of the final product, the performances of the processes and their environmental impact, depended on the fiber composition of the mix. Finally, the treatment of an industrial carton board revealed that mineral fillers contained in the material limited its upcycling.
Because of the low quality of the bleached pulp produced, another valorization way has been investigated: the production of oxidized cellulose for cellulose nanofibrils (NFC). A new pre-oxidation process for unbleached Kraft pulp has been developed, combining bleaching and oxidation of the substrate in a single stage including the use of TEMPO as a catalyst and oxidative agents commonly applied in fiber production lines. NFC of the same quality as those produced from bleached Kraft pulp by the classical TEMPO/NaClO/NaBr pre-oxidation system have been obtained. Other members of the jury
Stéphane GRELIER, Professor, Université de Bordeaux ♦♦ Renato FROIDEVAUX, Professor, Université de Lille ♦♦ Alain DUFRESNE, Professor, Grenoble INP-Pagora / LGP2 ♦♦ Anne-laurence DUPONT, Researcher, Muséum National d'Histoire Naturelle, Paris ♦♦ Damien EVRARD, Engineer, G-SCOP, Grenoble
11 February 2019 - Materials, Mechanical, Civil Engineering, Electrochemistry [Online thesis] Ph.D. title
Functionalization of cellulose nanofibrils for the development of biobased medical devices. Supervision Julien BRAS, Associate Professor HDR, Grenoble INP-Pagora / LGP2 ♦♦ Naceur BELGACEM, Professor, Grenoble INP-Pagora / LGP2 ♦♦ Elisa ZENO, Research Engineer (CTP) Abstract
In line with the ever-increasing academic and industrial interest for wood derived nanocellulose, the present work investigates the chemical surface modification of cellulose nanofibrils (CNFs) for biomedical application.
Drugs and prodrugs of active principle ingredients (APIs) were covalently immobilized or adsorbed onto CNFs films or suspensions. For covalent immobilization, the first strategy selected calls for water-based and single step esterification of CNF films. The resulting materials demonstrated antibacterial activity against both gram-positive and gram-negative bacterial strains, with a prolonged contact-active effect.
In the second strategy, CNFs suspensions were modified through a multistep reaction, involving amidation and click chemistry, still water-based. Highly innovative characterization tools, such as dynamic nuclear polarization (DNP) enhanced nuclear magnetic resonance (NMR), complemented well-established techniques to confirm the success of grafting.
In parallel to covalent immobilization, an adsorption strategy was also adopted, on both CNFs films and suspensions. Then, the CNF films with grafted or adsorbed APIs were used for preparing 100% CNF membrane for potential topical applications. Another component of this work used CNF suspensions with grafted or adsorbed APIs that were embedded in collagen matrices to prepare composites for designing soft tissue repair implants. Antibacterial activity against both aerobic and anaerobic bacteria, together with controlled release properties were assessed confirming that such composites present the expected active properties, and can be used for the design of innovative medical devices. Other members of the jury
Roberta BONGIOVANNI, Professor, Politecnico di Torino (Italy) ♦♦ Eva MALMSTRÖM JONSSON, Professor, KTH (Sweden) ♦♦ Timo LAAKSONEN, Professor, Université d’Helsinki (Finland) ♦♦ Yves BAYON, Senior R&D Manager, Medtronic
1st February 2019 - Materials, Mechanical, Civil Engineering, Electrochemistry Ph.D. title
Cellulose pretreatments for a nanofibrillation by twin-screw extrusion. Supervision Julien BRAS, Associate Professor HDR, Grenoble INP-Pagora / LGP2 Abstract
The CERISE project, conducted under the auspices of the Tec21 Laboratory of Excellence and the Carnot PolyNat Institute, aims to develop a new process for manufacturing cellulose nanofibrils (CNF) with a high dry matter content and low energy consumption. Twin screw extrusion (TSE) – industrially well-known energy-efficient and highly adaptable technique – was optimized to produce CNF at 20 % dry content. By decreasing considerably their water content, this new strategy improves their transport cost, their storage and extends their field of application.
The objectives were to
• Develop new pretreatments of cellulose fibers to facilitate the nanofibrillation and produce high quality functionalized CNF.
• Optimize TSE screw profile and conditions to produce CNF.
• Prepare new materials made of this new type of CNF.
Four chemical pretreatments, identified as easily industrializable, have been optimized. Extrusion nanofibrillation was simulated by software to obtain optimal extrusion conditions. This cost-effective approach was validated at semi-industrial scale. Various applications are considered for these new NFC with a high dry matter content. Other members of the jury
Carmen FREIRE, Professor, University of Aveiro (Portugal) ♦♦ Guy DELLA VALLE, Research Engineer, INRA Nantes ♦♦ Carlos VACA GARCIA, Professor, Université de Toulouse ♦♦ Nadia EL KISSl, CNRS Research Director, LRP, Grenoble ♦♦ Valérie MEYER, Research Engineer, CTP, Grenoble ♦♦ Antoine ROUILLY, Associate Professor, Toulouse INP ♦♦ Bruno VERGNES, Research Director, MINES ParisTech
11 January 2019 - Fluid Mechanics, Energy, Processes Ph.D. title
Production of glass fibre-based mats by a wet-laid process. Supervision Evelyne MAURET, Professor, Grenoble INP-Pagora / LGP2 ♦♦ Martine RUEFF, Research Engineer, Grenoble INP-Pagora / LGP2 Abstract
Glass fibre-based mats produced by a wetlaid process can be used, for example, as battery separators or insulation materials (core of vacuum insulation panels). These materials are mainly composed of submicron fibres, which are relatively expensive and can present health risks. This research project is a contribution to the study of the wet processing of fibreglass mats composed of relatively coarse fibres, where the final product must meet precise specifications. To carry out this work, we have been led to study the behaviour of glass fibres during the various stages of the process and to characterise the mats obtained. We were particularly interested in the physico-chemical behaviour of aqueous glass fibre suspensions. We characterized the contextual properties, tensile strength, compressibility and thermal conductivity of the fibre mats. The results obtained allowed us to propose an optimized formulation and process operating conditions. This new composition integrates reinforcing fibres in small quantities. It improves the mechanical characteristics without affecting other properties. Finally, we quantified the production costs and compared them to those of the process currently used with coarse fibres (dry-laid production). Other members of the jury
Didier CHAUSSY, Professor, Grenoble INP-Pagora / LGP2 ♦♦ Laurence LE COQ, Professor, IMT Atlantique ♦♦ Maria Angels PÈLACH SERRA, Professor, University of Girona, Spain