HAL Portal ESPCI (Ecole Supérieure de Physique et de Chimie Industrielles)
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Three-dimensional Meta-atoms for High Confinement of Mid-IR Radiation
No full textThe ability to confine photons into structures with highly sub-wavelength volumes is extremely interesting for many applications such as sensing, nonlinear optics, and strong light-matter interactions. However, their realization is increasingly difficult as the wavelength becomes shorter, due to fabrication challenges and increased metal losses. In this work, we present the first experimental characterization of three-dimensional circuit-like resonators operating in the mid-infrared. Through a combination of simulations, reflectivity measurements, and scanning near-field optical microscopy, we developed an analytical model capable of predicting the electromagnetic response of these structures based on their geometrical parameters. The design we studied offers a high degree of flexibility, enabling precise control over the resonant frequency of the various modes supported by the resonator, as well as independent control over radiative and non-radiative losses. Combined with the extreme field confinement demonstrated, these meta-atoms are highly promising for applications in detectors
Guided elastic waves in a highly-stretched soft plate
No full text12 pages 7 figures submitted to: American Physical Society - Physical Review XInternational audienceWe study the propagation of guided elastic waves in a plate made of Ecoflex, a nearly-incompressible elastomer. The in-plane displacement field in a soft plate is extracted. We measure the phase velocities of two in-plane modes and (first symmetrical Lamb mode) coexisting in the low frequency limit. While propagates at the transverse velocity, propagates at the plate velocity. The plate is then subjected to a nearly-uniaxial stress with an elongation reaching 120%. An induced anisotropy is first observed and then characterized by following the phase velocities of both modes in two principal directions. Although these measurements provide an estimate of the initial stress, they are not correctly predicted by the acousto-elastic theory. We thus show that the acousto-elastic theory alone is not sufficient to explain the evolution of velocities in a prestressed elastomer. The origin of this discrepancy is actually explained by the rheological properties of the elastomer, namely the frequency-dependent shear modulus. The implementation a fractional rheological model in the acousto-elastic theory enables a proper prediction for these velocities up to 80% elongation
Smartphone-assisted plasmonic biosensors for rapid on-site detection of foodborne pathogens and allergens
No full textInternational audienceWe report the design of a smartphone-assisted plasmonic immunosensor and its application to the detection of several food contaminants, namely staphylococcal enterotoxin A (SEA), bovine β-lactoglobulin (BLG), and hen egg white lysozyme (LYSO). Comprehensive characterization of antibodies was performed by ELISA and surface plasmon resonance imaging (SPR-i), demonstrating high affinity and specificity for each target, which supports their potential application in complex food matrices. The immunosensing platform utilizes gold nanoparticle-conjugated antibodies and inexpensive glass slides as single-use chips. Both qualitative visual detection by the naked eye down to around 1 ng of BLG, and quantitative detection with a portable spectrophotometer connectable to a smartphone are demonstrated. This self-contained device may provide a rapid, sensitive, and cost-effective approach to food contaminants analysis, potentially useful for on-site food safety assessment
Wide-field cellular-resolution retinal imaging using deformable mirror-based sensorless adaptive optics time-domain full-field OCT
No full textInternational audienceAdaptive optics (AO) enables cellular-resolution retinal imaging by correcting ocular aberrations, but its widespread clinical adoption remains limited by the narrow field of view (FOV) imposed by the isoplanatic patch of the eye. In this study, we present a deformable mirror (DM)–based sensorless AO time-domain full-field OCT (FFOCT) system that overcomes these limitations by leveraging the inherent robustness of FFOCT to ocular aberrations under spatially incoherent illumination. Using both phantom eye simulations and in vivo experiments, we demonstrate that correction of only three to five Zernike modes (defocus, astigmatism, and coma) is sufficient to significantly enhance SNR and resolve fine retinal structures. This includes reliable visualization of cone photoreceptors as close as 0.3 ∘ from the foveal center and depth-resolved imaging of inner retinal features such as nerve fiber bundles, vessel walls, capillaries, internal limiting membrane, macrophage-like cells, and Gunn’s dots, across a 5 ∘ ×5 ∘ FOV at 500 Hz. By simplifying AO implementation while achieving wide-field cellular resolution, this approach addresses key limitations of current AO ophthalmoscopes and offers a promising pathway toward a wider clinical deployment of high-resolution retinal imaging
Characterization of the oxygen properties of a hybrid glass chip designed for precise on chip oxygen control
No full textInternational audienceDespite its relevance in several research fields, the regulation of dissolved gas concentration in microfluidic chips remains overlooked. Precise control of dissolved oxygen levels is of importance for life science applications, especially for faithfully replicating in vivo tissue conditions in organ-on-chips. The current methods to control oxygen on-chip rely on the use of chemical scavengers, on the integration of an additional gas channel or on the perfusion of a liquid pre-equilibrated at a set oxygen level. However, for precise oxygen control, these microfluidic devices must be made from gas-impermeable materials. In this regard, glass is a material of choice due to its complete impermeability, but its microfabrication often requires specific clean room processes. Here, we report a low-tech fabrication method for a hybrid glass chip, which involves assembling glass components using an adhesion process. To evaluate this chip's suitability for use under highly controlled oxygen conditions, we developed a two-step assessment protocol. This involved determining the time needed to reach a target oxygen level during perfusion and measuring the reoxygenation time following the cessation of flow. Based on a dual approach of simulations and experiments, we emphasized crucial adhesive properties such as oxygen diffusion and solubility and proposed a range of well-suited adhesive materials. Finally, we demonstrated the interest of this hybrid glass chip for on-chip cell culture and cell respiration measurements. This work paves the way for broader accessibility in producing low tech gas-tight microfluidic chips for diverse applications
Prediction of Propene Hydroformylation using Machine Learning
No full textHere, we develop machine learning (ML) models to predict catalytic performance in rhodium-catalyzed propene hydroformylation and identify new ligands and reaction conditions for enhanced yield and selectivity. A curated dataset of 215 experimentally obtained data points involving [Rh(acac)(CO)₂] precatalyst and 49 phosphine ligands was used. Molecular, electronic, and reaction descriptors were constructed using cheminformatic representations and dimensionality reduction. Among several algorithms tested, XGBoost exhibited the best performance, achieving a root-mean-square error (RMSE) of 9.85% for iso-selectivity under leave-one-ligand-out cross-validation. Feature importance analysis revealed that ligand and solvent descriptors most strongly influence selectivity, whereas turnover number (TON) predictions were more challenging. A bootstrapped ensemble of XGBoost models integrated with a genetic algorithm enabled the exploration of vast ligand–condition space, yielding 58 candidate ligands predicted to achieve TON ≥ 330 and Iso(%) ≥ 70. This study demonstrates that interpretable ML models can complement mechanistic understanding and accelerate catalyst design for small-alkene hydroformylation
Highly efficient Hydrogenative depolymerisation of Polycaprolactone to 1,6-hexanediol
No full textInternational audienceWe report here our study on the development of an efficient process to make 1,6-hexanediol from the hydrogenation of polycaprolactone assisted by ethanolysis. Using a ruthenium SNS pincer catalyst, a record high turnover number of 19,600 with 98% yield of 1,6-hexanediol is obtained at 80 o C and 60 bar H2 pressure. The reported method has environmental advantages over the conventional process for the production of 1,6-hexanediol, which emits a significant amount of nitrous oxide greenhouse gas
Molecular aspects of cell-penetrating peptides: key amino acids, membrane partners, and non-covalent interactions
No full textInternational audienceSince the early 1990s, there has been considerable interest in cell-penetrating peptides (CPPs) capable of transporting various types of molecules in cells. These CPPs are endowed with the ability to cross the cell membrane by endocytosis and by other, as yet poorly understood, translocation pathways. Translocation involves interactions of the peptide with plasma membrane components before it can contact, disrupt, and/or reorganize the lipid bilayer. The plasma membrane is complex in terms of molecular composition and structure. It separates the external environment from the cell interior and is composed of thousands of different lipids, proteins, and sulfated carbohydrates, all arranged in a complex and dynamic manner and at various length scales. Floating above the lipid bilayer, negatively charged proteoglycans and other polysaccharides form a viscous, anionic matrix layer surrounding animal cells, which CPPs have to go through to reach the lipid bilayer. Even though the thickness and structure of this glycocalyx are extremely variable in different cell types, CPPs can cross ubiquitously cell membranes. On the peptide side, CPPs are mostly short (less than 30 amino acids), positively charged sequences. Some have also primary or secondary amphipathic properties. Understanding CPP translocation pathways requires interdisciplinary approaches from physical chemistry to cell biology for identifying key amino acids in the peptide sequence and membrane components, and the interactions between the two involved in the different steps of the process. In the following synthetic review, we focus on these aspects
Quantitative evaluation of methods to analyze motion changes in single-particle experiments
No full textInternational audienceThe analysis of live-cell single-molecule imaging experiments can reveal valuable information about the heterogeneity of transport processes and interactions between cell components. These characteristics are seen as motion changes in the particle trajectories. Despite the existence of multiple approaches to carry out this type of analysis, no objective assessment of these methods has been performed so far. Here, we report the results of a competition to characterize and rank the performance of these methods when analyzing the dynamic behavior of single molecules. To run this competition, we implemented a software library that simulates realistic data corresponding to widespread diffusion and interaction models, both in the form of trajectories and videos obtained in typical experimental conditions. The competition constitutes the first assessment of these methods, providing insights into the current limitations of the field, fostering the development of new approaches, and guiding researchers to identify optimal tools for analyzing their experiments
