The influence of high energy ion implantation on the properties of porous bioceramics coatings

L'augmentation de l'espérance de vie des populations des pays développés conduit à la pose de plus en plus fréquente d'éléments prothétiques ostéo-articulaires ou dentaires. En fonction du patient et de sa pathologie, leur remplacement peut être nécessairThe increase of life expectancy in developed countries led to enhance prosthetic elements utilization for bone joints and dentistry applications. Depending on the patient and his pathology, their replacement may be necessary more or less prematurely, du

The influence of high energy ion implantation on the properties of porous bioceramics coatings

L'augmentation de l'espérance de vie des populations des pays développés conduit à la pose de plus en plus fréquente d'éléments prothétiques ostéo-articulaires ou dentaires. En fonction du patient et de sa pathologie, leur remplacement peut être nécessaire plus ou moins prématurément en raison de la nécrose de l'os en contact avec la surface de l'implant. L'application de biocéramiques spécifiques à la surface de l'implant sous la forme de couche mince, suivie d'un traitement ionique à haute énergie, peut réduire sensiblement le remplacement des éléments prothétiques. Dans ce travail de thèse, nous cherchons à améliorer les propriétés mécaniques et l'adhésion des couches d'hydroxyapatite à la suite d'un traitement de surface employant un faisceau de particules à haute énergie. Trois différentes doses ont été implantées : 5'1015 1016 et 2.1016 ions·cm-2. L'amélioration des propriétés mécaniques des couches a été vérifiée à l'aide de techniques de nanoindentation et nanorayure; la modification des propriétés physico-chimiques a été mesurée grâce aux techniques RBS, NRA, DRIFTS, GXRD et EDX ; et la morphologie de surface a été abordée par des techniques AFM et MEB. À la fin de cette étude, des essais de dissolution en milieu biologique ont été mis en oeuvre. L'implantation ionique à haute énergie, appliquée avec une dose optimale et à une énergie d'accélération adaptée aux espèces implantées, conduit à des changements de topographie, à l'augmentation des propriétés mécaniques et à des modifications microstructurales des couches. L'ensemble de ces changements favorise le développement cellulaire lors des essais de dissolution in vitro.The increase of life expectancy in developed countries led to enhance prosthetic elements utilization for bone joints and dentistry applications. Depending on the patient and his pathology, their replacement may be necessary more or less prematurely, due to necrosis between bone and implant surface. The application of a bioceramic thin film onto the implant surface, followed by a treatment with high energy ions, can significantly reduce the replacement of prosthetic elements. In this thesis, we search for improve the mechanical properties and adhesion of hydroxyapatite layers deposited by pulsed laser deposition using a surface treatment of the deposit by using a beam of high energy particles. Three different doses were carried out : 5'1015 1016 and 2'1016 ions·cm-2. Improvement of mechanical properties of the layers were verified using nanoindentation and nanoscratch techniques; changes of physicochemical properties were measured by RBS, NRA, DRIFTS, GXRD and EDX techniques; and surface morphologies have been access by AFM and SEM techniques. At last, dissolution tests in biological environment have been implemented. The high energy ion implantation, applied to an optimal dose and adapted acceleration energy for a given implanted species leads to changes in topography, increasing mechanical properties and layer microstructural modifications. All these changes promote cell growth in in vitro dissolution test

Microfluidic elaboration of polymer microfibers from miscible phases: Effect of operating and material parameters on fiber diameter

International audienceBackground: fiber diameter is one of the most important morphological parameters which drives the applications of microfibers. This creates a need for the development of processes capable of producing a large variety of microfibers with a given diameter. To this regards, microfluidic spinning has recently emerged as an outstanding and simple technique for the production of micro- and nanofibers with controllable size and morphology.Methods: herein, microfibers were produced from (macro)monomers or prepolymers (core phase) by in situ photoirradiation using a capillary-based microfluidic device and a miscible sheath phase of various viscosity. The effects of the flow rate of both phases as well as the viscosity of the sheath fluid, the capillary dimensions and the monomer volume fraction in the core phase were thoroughly studied.Significant findings: by calculating the capillary number ratio from the ratios of sheath to core flow rate and viscosity, an empirical relationship which perfectly predicts the microfiber diameter as a function of monomer volume fraction, the capillary number ratio and capillary inner diameter but independent of its outer diameter is extracted. This result paves the way to the continuous-flow production of microfibers with well-controlled morphological characteristic

How Promoting and Breaking Intersurfactant H-Bonds Impact Foam Stability

On the basis of previous results revealing that intersurfactant H-bonds improve foam stability, we now focus on how foams stabilized by two different N-acyl amino acid surfactants are affected by different salts (NaF, NaCl, NaSCN), which can promote or break intersurfactant H-bonds. The chosen surfactants, namely, sodium N-lauroyl sarcosinate (C12SarcNa) and sodium N-lauroyl glycinate (C12GlyNa), differ only by one methyl group at the nitrogen of the amide bond that blocks intersurfactant H-bonds in the case of C12SarcNa. The salts were chosen because they are kosmotropic (NaF), chaotropic (NaSCN), and in between (NaCl) and thus influence the formation of an H-bond network in different ways. Surface tension measurements showed that the addition of salts decreased the cmcs of both surfactants and increased the packing density, as expected. Moreover, in presence of the salts, the head groups of the H-bond forming surfactant C12GlyNa were more tightly packed at the surface than the C12SarcNa head groups. The effect of the salts on foam stability was studied by analysis of the foam height, the foam liquid fraction, and by image analysis of the foam structure. As expected, the salts had no significant effect on foams stabilized by C12SarcNa, which is unable to form intersurfactant H-bonds. In contrast, the stability of C12GlyNa-containing foams followed the trend NaF > NaCl > NaSCN, which is in agreement with NaF promoting and NaSCN breaking intersurfactant H-bonds. Surface rheology measurements allowed us to correlate foam stability with surface elasticity. This study provides new insights into the importance of H-bond promoters and breakers, which should be used in the future design of tailor-made surfactants

PEEK (polyether-ether-ketone)-coated nitinol wire: Film stability for biocompatibility applications

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One-Step Generation of Alginate-Based Hydrogel Foams Using CO2 for Simultaneous Foaming and Gelation

International audienceThe reliable generation of hydrogel foams remains a challenge in a wide range of sectors, including food, cosmetic, agricultural, and medical applications. Using the example of calcium alginate foams, we introduce a novel foam generation method that uses CO2 for the simultaneous foaming and pH reduction of the alginate solution to trigger gelation. We show that gelled foams of different gas fractions can be generated in a simple one-step process. We macroscopically follow the acidification using a pH-responsive indicator and investigate the role of CO2 in foam ageing via foam stability measurements. Finally, we demonstrate the utility of interfacial rheology to provide evidence for the gelation process initiated by the dissolution of the CO2 from the dispersed phase. Both approaches, gas-initiated gelation and interfacial rheology for its characterization, can be readily transferred to other types of gases and formulations

Investigating Pore‐Opening of Hydrogel Foams at the Scale of Freestanding Thin Films

International audienceControlling the pore connectivity of polymer foams is key for most of their applications, ranging from liquid uptake, mechanics, and acoustic/thermal insulation to tissue engineering. Despite their importance, the scientific phenomena governing the pore-opening processes remain poorly understood, requiring tedious trial-and-error procedures for property optimization. This lack of understanding is partly explained by the high complexity of the different interrelated, multiscale processes which take place as the foam transforms from an initially fluid foam into a solid foam. To progress in this field, this work takes inspiration from long-standing research on liquid foams and thin films to develop model experiments in a microfluidic “Thin Film Pressure Balance.” These experiments allow the investigation of isolated thin films under well-controlled environmental conditions reproducing those arising within a foam undergoing cross-linking and drying. Using the example of alginate hydrogel films, the evolution of isolated thin films undergoing gelation and drying is correlated with the evolution of the rheological properties of the same alginate solution in bulk. The overall approach is introduced and a first set of results is presented to propose a starting point for the phenomenological description of the different types of pore-opening processes and the classification of the resulting pore-opening types