Simulation du procédé de nanoimpression thermiquesur silicium revêtu d'un film polymère ultramince

La nano-structuration des surfaces est un intrigant domaine de la physique des matériaux que l homme s est approprié aussi bien à des fins esthétiques que fonctionnelles. Les nanostructures peuvent être présentes à l état naturel (effet déperlant de la feuille de lotus) ou à l état artificiel pour répondre à des besoins techniques et peuvent alors être fabriquées par lithographie. Le procédé étudié dans cette thèse est la nanoimpression thermique qui permet de répliquer à moindre coût les micro- et nanostructures d un moule vers la surface d un substrat. Ce procédé d embossage consiste à imprimer le moule dans un film mince de polymère thermoplastique (50 à 500 nm d épaisseur) préalablement déposé sur le substrat. Eventuellement, une étape ultérieure de gravure permet de transférer dans ce dernier les motifs imprimés. On s intéresse en particulier à l évaluation des vitesses d impression des structures dans des films de polystyrène sur substrat de silicium. Un logiciel de simulation numérique a été développé ; il utilise la méthode des éléments naturels contraints (C-NEM). L accent a été mis sur la prise en compte de trois effets éminemment importants à l échelle nanométrique : tension de surface, mouillage, glissement à l interface fluide-solide. Combiné à un comportement visqueux non linéaire, cela permet de rendre partiellement compte des phénomènes physiques qui surviennent lors de l impression et d avoir des temps de simulation compatibles avec les contraintes industrielles tout en conservant une évaluation pertinente des vitesses d impression. Cette démarche nous place à mi-chemin entre des modèles analytiques très simples mais ayant un cadre d utilisation très restreint et des modèles plus complexes trop onéreux pour la simulation, comme la viscoélasticité en grandes transformations. Ces travaux abordent enfin le problème de la caractérisation du polymère à l échelle des films minces. Un des défis majeurs relevés ici consistait à appliquer à des films minces le comportement du polymère caractérisé à l échelle macroscopique. La validation expérimentale de toute la théorie élaborée a permis d appuyer cette démarche et d en révéler les limites. Ces approches théorique et expérimentale sont un premier pas vers la conception d un outil numérique d optimisation de la nanoimpression thermique.Surface nanostructuring is an intriguing field of materials physics that has been largely ado-pted for both aesthetic and functional purposes. Nanostructures can be present in nature (water repellent effect of the lotus leaf) or produced for industrial applications, and they can be manufactured by lithography. Thermal nanoimprint is the process studied in this thesis, which is an inexpensive method to replicate the micro- and nanostructures of a mold into the surface of a substrate. This embossing method consists in printing the mold into a thin film of thermoplastic polymer (50 to 500 nm in thickness) previously deposited on the substrate. A further etching step may transfer the imprinted patterns into the latter. The aim of this work is to evaluate the imprint speeds of the structures in thin polystyrene films on a silicon substrate. A numerical simulation software has been developed, which uses the Constrained Natural Elements Method (C-NEM). Our main contribution was to integrate three essential phenomena at the nanoscale: surface tension, wetting, and slip at the fluid-solid interface. Combined with a non-linear viscous behavior, this is shown to describe partially but sufficiently the physical phenomena that occur during printing. Therefore, this work lies halfway between simple analytical models, with a very limited scope of use, and complex models too expensive for simulation, such as finite strain viscoelasticity. Finally, this thesis addresses the problem of the characterization of a polymer in thin films. One of the major challenges faced here was to apply the macroscopic mechanical behavior to thin films. The experimental validation of the theory developed in the first part has corroborated this approach and revealed its limitations. This set of theoretical and experimental developments is a first step towards the design of a numerical tool for optimizing the thermal nanoimprint processPARIS-Arts et Métiers (751132303) / SudocSudocFranceF

Influence of thermal diffusion and shear-thinning during the leveling of nanoimprinted patterns in a polystyrene thin film

When capillary forces prevail, the leveling of the free surface of a fluid film is a natural phenomenon that has already found applicative interest either with brushmarks for paint coatings or for rheology on polymeric thin films. Among many parameters, the material behavior influences notably this phenomenon and its characterization still arouses curiosity at the nanoscale. In this article the nanoscale properties of a polystyrene film are derived from the leveling rate of nanoimprinted patterns and are compared to bulk values obtained with a parallel plate rheometer. In particular the focus is made on the isothermal assumption during the process and the consequences of an anisothermal state on the material behavior. Both points are investigated by using numerical simulations based on the natural element method. First we demonstrate experimentally that the leveling rate is influenced by the heat exchange at the air-polymer interface and that thermal diffusion should be taken into account within the film and its underlying substrate. Then we numerically investigate the influence of thermal diffusion and shear-thinning on the leveling rate. Finally we show that the bulk properties can represent particularly closely the behavior of the polymer at the nanoscale if adequate thermal boundary conditions are used and if shear-thinning is taken into account. This agreement postulates a decrease by 7◦C of the mean temperature of the polystyrene film coated on silicon when experiments are carried out on a hotplate at 100◦C in a cleanroom environment

Organization of Block Copolymers using NanoImprint Lithography: Comparison of Theory and Experiments

We present NanoImprint lithography experiments and modeling of thin films of block copolymers (BCP). The NanoImprint lithography is used to align perpendicularly lamellar phases, over distances much larger than the natural lamellar periodicity. The modeling relies on self-consistent field calculations done in two- and three-dimensions. We get a good agreement with the NanoImprint lithography setups. We find that, at thermodynamical equilibrium, the ordered BCP lamellae are much better aligned than when the films are deposited on uniform planar surfaces

Sporadic renal cell carcinoma in young and elderly patients: are there different clinicopathological features and disease specific survival rates?

BACKGROUND: Sporadic renal cell carcinoma (RCC) is rare in young adults. In the present retrospective study we reviewed clinicopathological features and disease specific survival rates in young patients (≤45 years) with RCC and compared them to old patients (≥75 years) with RCC. METHODS: Between 1992 and 2005 a total of 1042 patients were treated for RCC at our institution. We found 70 patients 45 years or younger (YP) and 150 patients 75 years or older (OP) at time of diagnosis. There were no differences in therapeutical approaches between both groups. Clinical and biologic parameters at diagnosis were compared and subjected to uni- and multivariate analysis to study cancer specific survival and progression rate. Mean postoperative follow-up in both groups was 50.1 months. RESULTS: Mean age was 39 years in YP and 80 years in OP, respectively. YP demonstrated significantly lower stage (pT1-pT2 N0 M0, p = 0.03), lower tumor grade (p = 0.01) and higher male-to-female ratio (p < 0.001). The rate of lymph node metastases or distant metastatic disease at presentation did not differ significantly between both groups. In multivariate analysis young age was independently associated with a higher 5-year cancer specific survival (95.2% vs. 72.3%, p = 0.009) and a lower 5-year progression rate (11.3% vs. 42.5%, p = 0.002). CONCLUSION: Sporadic RCC in young patients have lower tumor stages and grades and a better outcome compared to elderly. Age≤45 years was an independent prognostic factor for survival and progression

Identification of Clinically Relevant Protein Targets in Prostate Cancer with 2D-DIGE Coupled Mass Spectrometry and Systems Biology Network Platform

Prostate cancer (PCa) is the most common type of cancer found in men and among the leading causes of cancer death in the western world. In the present study, we compared the individual protein expression patterns from histologically characterized PCa and the surrounding benign tissue obtained by manual micro dissection using highly sensitive two-dimensional differential gel electrophoresis (2D-DIGE) coupled with mass spectrometry. Proteomic data revealed 118 protein spots to be differentially expressed in cancer (n = 24) compared to benign (n = 21) prostate tissue. These spots were analysed by MALDI-TOF-MS/MS and 79 different proteins were identified. Using principal component analysis we could clearly separate tumor and normal tissue and two distinct tumor groups based on the protein expression pattern. By using a systems biology approach, we could map many of these proteins both into major pathways involved in PCa progression as well as into a group of potential diagnostic and/or prognostic markers. Due to complexity of the highly interconnected shortest pathway network, the functional sub networks revealed some of the potential candidate biomarker proteins for further validation. By using a systems biology approach, our study revealed novel proteins and molecular networks with altered expression in PCa. Further functional validation of individual proteins is ongoing and might provide new insights in PCa progression potentially leading to the design of novel diagnostic and therapeutic strategies

Gene-rich UV sex chromosomes harbor conserved regulators of sexual development

Centro de Investigación Forestal (CIFOR)Nonrecombining sex chromosomes, like the mammalian Y, often lose genes and accumulate transposable ele ments, a process termed degeneration. The correlation between suppressed recombination and degeneration is clear in animal XY systems, but the absence of recombination is confounded with other asymmetries between the X and Y. In contrast, UV sex chromosomes, like those found in bryophytes, experience symmetrical population genetic conditions. Here, we generate nearly gapless female and male chromosome-scale reference genomes of the moss Ceratodon purpureus to test for degeneration in the bryophyte UV sex chromosomes. We show that the moss sex chromosomes evolved over 300 million years ago and expanded via two chromosomal fusions. Although the sex chromosomes exhibit weaker purifying selection than autosomes, we find that suppressed recombination alone is insufficient to drive degeneration. Instead, the U and V sex chromosomes harbor thousands of broadly expressed genes, including numerous key regulators of sexual development across land plants.This work was supported by NSF DEB-1541005 and 1542609 and start-up funds from UF to S.F.M.; microMORPH Cross-Disciplinary Training Grant, Sigma-Xi Grant-In-Aid of Research, and Society for the Study of Evolution Rosemary Grant Award to S.B.C.; NSF DEB-1239992 to N.J.W.; the Emil Aaltonen Foundation and the University of Turku to S.O.; and NSF DEB-1541506 to J.G.B. and S.F.M. The work conducted by the U.S. Department of Energy Joint Genome Institute was supported by the Office of Science of the U.S. Department of Energy under contract no. DE-AC02-05CH11231.Peer reviewed12 Pág. Supplementary material for this article is available at http://advances.sciencemag.org/cgi/ content/full/7/27/eabh2488/DC