ED Sciences Chimiques
Contribution to the eco-design of printed MEMS piezoelectric energy harvesters: influence of materials, formulations, and processes
by Nadia BENCHAREF (ICMCB - Institut de Chimie de la Matière Condensée de Bordeaux)
The defense will take place at 9h30 - Amphi ICMCB 87 Avenue du Dr Albert Schweitzer, 33600 Pessac
in front of the jury composed of
- Catherine ELISSALDE - Directrice de recherche - ICMCB-CNRS - Directeur de these
- Charles MANIERE - Chargé de recherche - Crismat-CNRS - Rapporteur
- Nadège REVERDY-BRUAS - Professeure des universités - LGP2- Pagora Grenoble INP - Rapporteur
- Barbara LAFARGE - Maîtresse de conférences - Université de technologie de Compiègne - Examinateur
- Philippe POULIN - Directeur de recherche - CRPP-CNRS - Examinateur
- Claude ESTOURNES - Directeur de recherche - CIRIMAT-CNRS - Examinateur
- Cyril AYMONIER - Directeur de recherche - ICMCB-CNRS - Examinateur
- Hélène DEBEDA - Professeure des universités - IMS-Université de Bordeaux - CoDirecteur de these
Vibrational energy harvesting via the piezoelectric effect is a promising approach for powering miniaturized systems. These devices have been the subject of extensive research aimed at improving their electromechanical performance and technological integration. However, efforts must now be made to reduce their environmental footprint, taking into account the choice of materials, fabrication processes, and energy consumption during manufacturing. In this context, this thesis aims to develop an eco-innovative approach for the fabrication of printed MEMS piezoelectric energy harvesters with a low environmental footprint. The material selected for this study is (K,Na)NbO3 (KNN), one of the most promising lead-free piezoelectric materials. Nevertheless, it is limited by the difficulty of controlling its stoichiometry, due to the volatility of the alkali elements when sintering is performed at high temperatures to achieve optimal densification. Therefore, particular attention was paid to Spark Plasma Sintering (SPS), which enables rapid densification at low temperatures. One of the targeted specifications is optimal densification in a single step, without the SPS post-annealing often required due to the low partial pressure of oxygen during sintering. A study to optimize sintering parameters was therefore conducted on bulk ceramics. The objective was to identify the critical parameters needed to achieve optimized microstructures, in order to simultaneously ensure the material's functional performance and a reduced environmental footprint. A dense (96%) KNN ceramic was obtained in a single step at 700°C via SPS. However, the poor piezoelectric performance observed, attributed to a fine and inhomogeneous microstructure, required the exploration of alternative optimization approaches. Specific levers of the SPS process were exploited, in particular the use of fast heating rates and variations in the ON-OFF current pulse sequence. The objective was to promote grain growth and microstructural homogeneity in terms of grain size distribution. The use of a fast heating rate of 400 °C/min combined with a 9-9 pulse sequence resulted in a dense ceramic (96%) with a homogeneous microstructure and a piezoelectric coefficient d33 of 72 pC/N. The SPS parameters optimized for bulk ceramics were then transferred and adapted for the co-sintering of multilayers structures consisting of an active piezoelectric material deposited between two electrodes. Their fabrication using thick-film screen-printed layers is an attractive approach, compatible with low-cost manufacturing and minimizing material loss. An aqueous KNN ink was developed. This formulation reduces emissions associated with the organic compounds found in conventional formulations, eliminating the need for a debinding step before sintering. A specially designed SPS mold was used to protect the layered stack and ensure uniform pressure application. The co-sintering temperature was lowered to 570 °C for a 3-minute holding time. After sintering, the active KNN layer was well densified. The interfaces between the KNN layer and the electrodes show strong adhesion. Furthermore, a life-cycle analysis of MEMS devices highlighted the significant contribution of the electrodes to the overall environmental footprint. Bearing this in mind, the passive substrate was used as the bottom electrode. The quality of the interface between the KNN layer and the steel substrate was demonstrated. The first electromechanical measurements confirm the potential of this approach for the development of performance and eco-responsible MEMS piezoelectric energy harvesters.
ED Sciences de la Vie et de la Santé
Genomic fingerprints of selection and the effect of genetic variation on apricot phenotypes: Focus on structural variants
by Ismaël BLANCHARD (BFP - Biologie du Fruit et Pathologie)
The defense will take place at 14h00 - Salle 1, Amphithéâtre Colette & Josy Bové Centre de recherche INRAE, 71 avenue Edouard Bourlaux, 33140 Villenave-d'Ornon
in front of the jury composed of
- Véronique DECROOCQ - Directrice de recherche - Université de Bordeaux - Directeur de these
- Dominique THIS - Professeure - Institut Agro Montpellier - Rapporteur
- Odile LECOMPTE - Professeure des universités - Université de Strasbourg - Rapporteur
- Morgane ROTH - Chargée de recherche - Inrae - Examinateur
- Laurence MOREAU - Directrice de recherche - Inrae - Examinateur
Genetic diversity is a major component of the adaptive potential of organisms facing environmental, biotic, and agronomic constraints. In plant species, domestication and breeding over the last millennia have used only a limited fraction of this diversity, much of which remains to be characterized and exploited. This diversity has long been described mainly through simple variants, such as nucleotide substitutions, whereas structural variants, presence/absence variation, and sequences missing from reference genomes can strongly affect our understanding of gene structure and function. Cultivated apricot (Prunus armeniaca) and related species of the Armeniaca section therefore represent an important model for studying the evolution of perennial fruit trees, domestication, and adaptation to major agronomic constraints. This thesis aims to build, characterize, and exploit an Armeniaca pangenome in order to better represent the genomic diversity of P. armeniaca, P. sibirica, and P. mandschurica, and to assess the role of structural variants in genome evolution and genotype–phenotype relationships. The first part of this thesis consisted in establishing a pangenome from complete genomes generated with long-read assemblies and integrated into a phylogeny-guided pangenome graph. This resource overcomes the limits of a single reference genome and describes the genomic landscape of European and Chinese cultivated apricots, wild Central Asian forms, and related species. The resulting pangenome reveals substantial diversity, with approximately 25 million SNPs and more than 537,000 structural variants. The analyses show that different phylogeographic groups contribute unevenly to pangenome expansion, particularly through specific or rare sequences. They also indicate that transposable elements are a major driver of structural variation, especially insertions and deletions. The study of the DAM locus, involved in dormancy and budbreak, illustrates the functional value of a graph-based representation for exploring complex regions and validating structural configurations that are difficult to observe with a single linear reference The second part focused on the functional and population-level importance of structural variants. Once detected in the pangenome, these variants were genotyped in apricot populations to compare their distribution among distinct genetic groups, especially domesticated, wild, and related material, and to evaluate their potential contribution to phenotype variation. Two genotyping strategies, DELLY and PanGenie, were initially compared using a sharka resistance-related phenotype. PanGenie was selected for subsequent analyses because it provides a denser matrix more directly derived from the pangenome. Genome wide association analyses were then extended to traits of interest for breeding and vegetative propagation: rooting ability, grafting success, and budbreak measured as the sum of growing degree hours required to reach the budbreak stage Overall, this thesis provides both an original genomic resource for the Armeniaca section and a methodological framework connecting pangenome construction to the functional exploitation of structural variants. It shows that pangenome graphs can better represent domesticated and wild genetic diversity, overcome the limits of a linear reference, and open new perspectives for identifying loci associated with adaptation, domestication, and apricot improvement.
Thalamocortical bases of decision-making in uncertain environment
by Emma MARILLAT (Institut de neurosciences cognitives et intégratives d'Aquitaine)
The defense will take place at 14h00 - Amphithéatre BBS Bâtiment Bordeaux Biologie Santé, 2 Rue Dr Hoffmann Martinot, 33000 Bordeaux
in front of the jury composed of
- Mathieu WOLFF - Directeur de recherche - CNRS / Université de Bordeaux - Directeur de these
- Emmanuelle COURTIOL - Chargée de recherche - CNRS / Université de Lyon - Rapporteur
- Romain GOUTAGNY - Directeur de recherche - CNRS / Université de Strasbourg - Rapporteur
- Agnes NADJAR - Professeure des universités - Université de Bordeaux - Examinateur
Decision-making in uncertain environments relies on a dynamic balance between exploring new options and exploiting choices already known to be advantageous. Understanding the neural substrates of this balance is a major challenge in cognitive neuroscience. The orbitofrontal cortex (OFC) and the mediodorsal thalamic nucleus (MD) appear to be key players in adaptive decision-making, but the functional interactions between these regions remain poorly characterized. To investigate this question, we used a "three-armed bandit" instrumental task in which the most favorable option (one lever among three) varies over time, forcing animals to alternate between exploration and exploitation strategies. We first established that lesioning the OFC or the MD produces a specific deficit in this task, reflected as a difficulty in recovering optimal performance when the most favorable option is switched. Importantly, we also established that lesioning the submedius thalamus, the other major thalamic afferent to the OFC, has no effect. In addition, a viral neuroanatomical tracing strategy allowed us to establish that although the thalamocortical pathways originating from the MD and the Sub both converge onto the OFC, they predominantly contact different cortical neuronal populations. Taken together, these data suggest the existence of two anatomically and functionally distinct thalamocortical circuits within the OFC. To further clarify the functional role of the OFC-MD circuit, we then assessed the functional contribution of each region using a fiber photometry approach in animals performing the task. We observed that OFC activity increases both at the time of choice and when a reward is obtained, indicating that the choice and its reinforcement appear to be represented at the cortical level. In contrast, thalamic activity is modulated neither by the choice nor by the reward, as the MD shows increased activity only when the animal evaluates the consequences of its choice. Interestingly, this thalamic activation appears to result from learning, since the MD is essentially silent in naive animals. This dynamic thus suggests that the MD does not directly encode reward value, but rather contributes to the maintenance and consolidation of optimal choice strategies by potentially influencing prefrontal regions at the moment when the current value representation of the choice may be called into question. Taken together, these data indicate a distinct and complementary specific functional contribution of the OFC and the MD, ensuring the implementation of adaptive strategies when an abrupt change occurs in the environment. These results obtained in rodents converge with earlier work conducted in human and non-human primates, suggesting broad conservation of the functional organizational principles of thalamocortical circuits across the phylum. Alterations in thalamocortical connectivity are a recurrent symptom in numerous psychiatric disorders, such as addictive disorders, schizophrenia, or obsessive-compulsive disorder. Better understanding the functional organizational principles of thalamocortical circuits could therefore pave the way toward improved management of the alterations in behavioral flexibility and decision-making seen in these mental disorders.
Molecular and anatomical characterisation of grape seeds (cv Merlot) during berry ripening: applications in œnology.
by Julien FOISNON (Oenologie)
The defense will take place at 14h00 - Amphitéatre ISVV 210 Chemin de Leysotte 33140 Villenave-d'Ornon
in front of the jury composed of
- Régis GOUGEON - Professeur des universités - Université de Bourgogne - Rapporteur
- Jérémy LOTHIER - Professeur - Université d'Angers - Rapporteur
- Natalia QUIJADA-MORIN - Maîtresse de conférences - Université de Bourgogne - Examinateur
- Arnaud LANOUE - Maître de conférences - Université de Tours - Examinateur
Although red wine vinification utilizes the entire grape berry (Vitis vinifera L.), the seed remains an underexplored anatomical structure, traditionally relegated to the sole role of a condensed tannin reservoir. Knowledge regarding its tissue organization relies on fragmentary historical data, and its biochemical evolution dynamics during ripening remain largely unknown outside of its polyphenolic fraction. This doctoral research offers an in-depth characterization of grape seed biology to reassess its functional role and oenological potential. Based on a detailed kinetic monitoring from cluster closure to overripeness, a multi-scale analytical approach was deployed: Anatomical and structural characterization: The combination of histological sections with non-destructive three-dimensional imaging (CT scan and X-ray microtomography) allowed the establishment of a precise spatio-temporal mapping of seed development. These observations were complemented by monitoring the incorporation of structural macromolecules (lignin, cutin, and suberin), which are key elements in seed coat ontogeny and stiffening. Metabolomic exploration and transfer dynamics: Through an untargeted approach, a comprehensive catalog of the seed's molecular diversity was established. This profiling enabled tracing the synthesis kinetics of these compounds and tracking their fate and transfer into the liquid medium during vinification. Altogether, this work provides major fundamental advances in the understanding of grape seed development. Anatomically, it reveals the precise chronology of lignification and the establishment of polyester barriers (cutin/suberin), thereby redefining the functional organization of seed coats. Biochemically, the characterization of the metabolome proves that the seed possesses a molecular footprint of unsuspected complexity, extending far beyond its tannic fraction. Demonstrating the transfer of these non-polyphenolic metabolites into wine reassesses the seed's role as a direct contributor to the chemical composition and organoleptic signature of wines. Finally, mastering these physicochemical characteristics offers rational perspectives for its valorisation. Particularly through thermal treatment to be used as a new method of spirits aging.
ED Sciences Physiques et de l'Ingénieur
INTEGRATED PHOTONIC ARCHITECTURES INSCRIBED BY FEMTOSECOND LASER
by Mathis CARPENTIER (ICMCB - Institut de Chimie de la Matière Condensée de Bordeaux)
The defense will take place at 14h00 - Amphithéâtre ICMCB – UMR5026 87, Avenue du Docteur Schweitzer, 33608 PESSAC cedex
in front of the jury composed of
- Yannick PETIT - Maître de conférences - Université de Bordeaux - ICMCB – UMR5026 - Directeur de these
- Pavel LOIKO - Chargé de recherche - CIMAP - UMR 6252 - Rapporteur
- Lionel CANIONI - Professeur - Université de Bordeaux - ICMCB – UMR5026 - CoDirecteur de these
- Elise GHIBAUDO - Professeure - CROMA - MINATEC - G-INP - IUT 1 de Grenoble - Rapporteur
- Jérome NEAUPORT - Directeur de recherche - CEA - Examinateur
- Emmanuel ABRAHAM - Professeur - Université de Bordeaux - LOMA - UMR 5798 - Examinateur
Femtosecond laser inscription is a versatile and highly efficient approach to induce modifications in a wide range of materials, compatible with a broad spectrum of photonic applications spanning from the visible to the mid-infrared. Focusing a femtosecond laser beam into the bulk of innovative materials enables the design and fabrication of multiscale 3D photonic structures, ranging from the (sub-)micrometer to the centimeter scale. In this thesis work, we exploit this technique to develop photonic components that are (i) passive, such as waveguides and periodic structures like volume or integrated Bragg gratings, and (ii) active, through the realization of optical amplification in the near-infrared. In collaboration with materials science specialists, the conducted research relies on original laser-matter interaction mechanisms within innovative glass matrices specially sensitized by silver incorporation. Indeed, femtosecond laser irradiation selectively activates silver photochemistry within such tailored glass matrices. This has enabled the realization of transmission volume Bragg gratings (in the visible and near-infrared) as well as waveguides with integrated Bragg gratings, the latter exhibiting an attenuation at the Bragg resonance of up to 99.7% over record grating lengths as short as 500 µm, corresponding to coupling coefficients on the order of 7 mm⁻¹. Furthermore, the study of silver-photosensitive glasses co-doped with rare-earth ions (Ytterbium and Neodymium) allowed to generalize and exploit the strong, highly localized energy transfer between laser-created silver clusters and the co-incorporated rare-earth ions. This enables spatially localized infrared emission, despite the homogeneous distribution of the infrared emitters, leading to the demonstration of a waveguide amplifier via indirect pumping. In addition, a novel bismuth-based photochemistry was explored within phosphate glasses. The optically induced local refractive index variations are correlatively accompanied by changes in the oxidation state of Bismuth ions, providing access to extended spectroscopic properties covering the telecom O-band (around 1300 nm), a spectral region relatively poorly covered by coherent sources. An amplification of 2 dB/W/cm was thus achieved at 1345 nm under 976 nm pumping within an inscribed waveguide, showing great promise for medical applications. Finally, we initiated the exploration of novel heavy oxide glasses (Barium-Germanium-Gallium) via laser irradiation for mid-infrared applications. Overall, this thesis provides novel all-optical realizations of photonic components towards the development of future photonic platforms.
Terahertz Phase Imaging: from Emerging Computational Techniques to Resolution Enhancement
by Pitambar MUKHERJEE (Laboratoire de l'Intégration du Matériau au Système)
The defense will take place at 10h00 - Amphithéâtre J.P. Dom IMS, Laboratoire de l'Intégration du Matériau au Système, Université de Bordeaux, 351 Cours de la Libération, 33405 Talence Cedex
in front of the jury composed of
- Patrick MOUNAIX - Directeur de recherche - Université de Bordeaux - Directeur de these
- Frédéric TEPPE - Directeur de recherche - Université de Montpellier - Rapporteur
- Alexandre LOCQUET - Chargé de recherche - Georgia Institute of Technology - Rapporteur
- Frédéric GARET - Professeur des universités - Site de Chambéry - Université Savoie Mont Blanc - Examinateur
- Lionel CANIONI - Professeur des universités - Université de Bordeaux - Examinateur
- Damien BIGOURD - Chargé de recherche - Université de Bordeaux - Examinateur
Technological advancements in the terahertz (THz) spectral domain have significantly accelerated the efficiencies of THz imaging systems. In traditional imaging configurations, a visible image is formed due to the interaction of the specimen with incident light. When light passes through a sample, it gets absorbed by distinct areas of the sample. This creates changes in brightness or amplitude contrast that can help us to see the sample's structure. However, many biological and industrial objects show major differences in their light-bending (refractive index) properties rather than their light-absorbing characteristics. As a result, imaging techniques based on intensity-only measurements may not reveal all the details of such objects and often provide poor contrast while imaging transparent or dense objects. Improvement in image contrast can be achieved with the help of staining and labeling techniques. But such techniques can hamper imaging samples. To overcome these limitations, phase-sensitive imaging comes into play, providing crucial information about the specimen. Phase imaging in the THz regime has emerged as a scientifically fertile yet computationally underdeveloped research area. Researchers have explored several imaging techniques, ranging from time-domain spectroscopic imaging (TDS) to continuous-wave (CW) imaging, to advance phase-sensitive imaging in the THz domain. But these techniques have inherent disadvantages associated with data acquisition, experimental complexity, detector sensitivity, algorithmic convergence, and space-bandwidth product (SBP). Such constraints collectively hinder THz imaging systems from performing high-resolution phase imaging. The motivation of this thesis lies in addressing these challenges by developing advanced computational algorithms and high-resolution phase imaging modalities. As a first step toward this goal, a second-order optimization (quasi-Newton optimization) scheme is developed to improve phase-reconstruction accuracy by iteratively computing the analytical expressions for both the first-order and second-order derivatives of the cost function. This approach enables phase-sensitive imaging from multi-plane intensity measurements with improved convergence and reconstruction accuracy compared to the existing conventional THz phase imaging techniques. Subsequently, multi-angle illumination-based computational imaging methods are investigated for high-SBP imaging in the THz domain. In this context, a time-resolved synthetic aperture imaging approach in the Fourier domain is first numerically explored, employing a Nesterov-accelerated gradient-descent-based computational framework to solve the phase-retrieval problem. Finally, THz Fourier Ptychographic imaging is performed utilizing a CW THz imaging system, where the multi-angle illumination is outputted by a motorized kinematic mirror. In this method, an iterative phase-retrieval algorithm (aberration-corrected) is combined with an illumination angle calibration approach (circular edge-detection-based) to perform phase imaging in the THz spectral range with improved spatial resolution. To summarize, in this work, advanced computational strategies are developed for accurate and high-resolution phase-sensitive imaging in the THz regime, which demonstrate their effectiveness for improving phase reconstruction, convergence speed, and spatial resolution.