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The intriguing role of L-cysteine on the modulation of chiroplasmonic properties of chiral gold nano-arrows
No full textInternational audienc
The 2025 motile active matter roadmap
No full textInternational audienceActivity and autonomous motion are fundamental aspects of many living and engineering systems. Here, the scale of biological agents covers a wide range, from nanomotors, cytoskeleton, and cells, to insects, fish, birds, and people. Inspired by biological active systems, various types of autonomous synthetic nano- and micromachines have been designed, which provide the basis for multifunctional, highly responsive, intelligent active materials. A major challenge for understanding and designing active matter is their inherent non-equilibrium nature due to persistent energy consumption, which invalidates equilibrium concepts such as free energy, detailed balance, and time-reversal symmetry. Furthermore, interactions in ensembles of active agents are often non-additive and non-reciprocal. An important aspect of biological agents is their ability to sense the environment, process this information, and adjust their motion accordingly. It is an important goal for the engineering of micro-robotic systems to achieve similar functionality. Many fundamental properties of motile active matter are by now reasonably well understood and under control. Thus, the ground is now prepared for the study of physical aspects and mechanisms of motion in complex environments, the behavior of systems with new physical features like chirality, the development of novel micromachines and microbots, the emergent collective behavior and swarming of intelligent self-propelled particles, and particular features of microbial systems. The vast complexity of phenomena and mechanisms involved in the self-organization and dynamics of motile active matter poses major challenges, which can only be addressed by a truly interdisciplinary effort involving scientists from biology, chemistry, ecology, engineering, mathematics, and physics. The 2025 motile active matter roadmap of Journal of Physics: Condensed Matter reviews the current state of the art of the field and provides guidance for further progress in this fascinating research area
La substitution de cations à l'état de valence déséquilibré a induit des centres de couleur dans les hétérocristaux de pérovskite sans plomb, permettant une réponse photoélectrique du visible à la longueur d'onde supérieure à 1 300 nm
No full textInternational audienceLead-free halide double perovskite (HDP) Cs2NaInCl6 has become a critical material for photoelectric applications due to its favorable optoelectronic properties. However, the limited light absorption range and lack of a carrier separation driving force hinder its utilization as high-performance wide-spectrum photodetectors. Here, we achieved epitaxial growth of Cs2NaInCl6/Cs2NaInCl6: Sb (Ⅴ) (CNIC/CNIC-Sb) hetero-crystals via temperature and solvent solubility engineering, and the hetero-crystals featured with extended photon absorption from ultraviolet (UV) to near-infrared (NIR) (up to 1300 nm). High-resolution transmission electron microscopy (HTEM) and Raman mapping characterizations of the hetero-crystals elucidate that the reduced lattice mismatch enables epitaxial growth. The extended-edge X-ray absorption fine structure spectroscopy (EXAFS) and electron paramagnetic resonance (EPR) measurement characterizations gain insight into the origin of the NIR absorption in Sb (Ⅴ) doped CNIC. The results unveil that substitution In (III) with Sb (Ⅴ) in the lattice would generate Na (Ⅰ) vacancies due to meeting the total charge balance, also known as a color center (also called F-center) in metal halide crystal. The color centers are correlated with the light-induced formation of localized trap states, which are associated with Na (Ⅰ) vacancies and Frenkel defects contributing to NIR absorption. Moreover, Kelvin probe force microscopy (KPFM) measurement validates the built-in potential at the epitaxy hetero-crystal interface. Consequently, the photodetectors (PDs) based on CNIC/CNIC-Sb hetero-crystals achieve self-driving NIR photoresponse with a detectivity of 1.28×10^12 Jones at 1310 nm. Our findings offer a design approach for hetero-crystals, paving the way for non-toxic, wide-spectrum, high-temperature-tolerance PDs
Sliding of liquid droplets on thin viscoelastic soft layers
No full textInternational audienceSoft substrates are deformed by liquid-vapor surface tension upon contact with liquid droplets, forming the well-known wetting ridge. This ridge dynamically propagates with the moving contact line and critically influences liquid spreading. Here, we experimentally investigate gravity-driven sliding dynamics of water droplets on vertically tilted silicone layers whose viscoleasticity is characterized by the Chasset-Thirion model with the exponent m. At low Bond numbers, the sliding velocity scales with droplet size as V S ∼ D 2 m . While in the thin-film limit, velocity exhibits a pronounced power-law dependence on nominal substrate thickness, V S ∼ Π(h) -1 m . We rationalize these observations by quantifying viscoelastic dissipation within the soft layer and balancing it against the gravitational driving force using an energy-conservation framework. Our findings offer novel avenues for designing advanced soft coatings, anti-fouling and self-cleaning surfaces, and biomedical devices.</div
Feature-Resolved Photoluminescence Analysis: Probing Emission Beyond Conventional Photon Statistics
No full textWe present a feature-resolved methodology to analyse the photoluminescence dynamics of single emitters using a combination of lifetime, spectral, and photon correlation analyses. By integrating conventional ensemble photon statistics measurements with emission state-resolved, spectrally filtered, and lifetime-gated methods, we uncover emission dynamics that remain hidden in ensemble treatment. We study the fluorescence of single CdSe/CdS core/shell colloidal quantum dots under varying excitation powers. Using feature-resolved analysis, we understand the radiative and non-radiative recombination processes, and estimate quantum parameters. Event-selective analysis provides a versatile toolkit for characterizing emitters, both single and aggregate particles. These methods are broadly applicable to a wide class of photoluminescent emitters, such as nitrogen vacancy centres in nanodiamond, epitaxial quantum dots, and perovskite nanocrystals. The application of these lateral investigation techniques will contribute to the advancement of quantum light source development
Hopper flows of dense suspensions: a 2D microfluidic model system
No full textInternational audienceAbstract Flows of particles through bottlenecks are ubiquitous in nature and industry, involving both dry granular materials and suspensions. However, difficulties in precisely controlling particle properties in conventional set-ups hinder the full understanding of these flows in confined geometries. Here, we present a microfluidic model set-up to investigate the flow of dense suspensions in a two-dimensional hopper channel. Particles with controlled properties such as shape and deformability are in situ fabricated with a photolithographic projection method and compacted at the channel constriction using a Quake valve. The set-up is characterised by examining the flow of a dense suspension of hard, monodisperse disks through constrictions of varying widths. We demonstrate that the microfluidic hopper discharges particles at a constant rate under both imposed pressure and flow rate. The discharge of particles under imposed flow rate follows a Beverloo-like scaling, while it varies nonlinearly with particle size under imposed pressure. Additionally, we show that the statistics of clog formation in our microfluidic hopper follow the same stochastic laws as reported in other systems. Finally, we show how the versatility of our microfluidic model system can be used to investigate the outflow and clogging of suspensions of more complex particles
Measure of high contact angles
No full textInternational audienceThe contact size of a non-wetting drop being sensitive to contact angle and gravity, its variation with drop size is an excellent marker of the value of the contact angle
Snooping Helices : The elastic path finding algorithm of growing hyphae
No full textAccepté pour publication dans PNASInternational audienceProprioception is the integrated sense of self-movement and body position in complex organisms. Herewe describe a novel, mechanical form of proprioception driving directional choice making in tip-growinghelical organisms. We show that C. albicans hyphae utilize their built-in helicity as an environment-scanning mechanism to explore their surrounding and find target surfaces for invasion. When confined tosurfaces, hyphae continue producing in-plane oscillatory shapes that promote further invasive behavior.C. albicans’ inherent mechanical instabilities regulate the switching of growth direction and their abruptdirectional decisions can be understood as elastic bifurcations of squeezed, confined helices
Modeling neurodegenerative diseases in Drosophila is conditioned by stress resistance and gut microbiome composition of the reference line
No full textDrosophila is widely used to study the pathological mechanisms of human diseases in vivo , including metabolic and neurological disorders. In these models, disease-induced alterations in locomotion and stress resistance are generally monitored in comparison to healthy control flies, such the white-eyed strain w 1118 , used as a reference for normal physiology and behavior. Here we compared two independent w 1118 lines and found that they differed strikingly in their susceptibility to oxidative stress and nutrient starvation, and less markedly in their locomotor performance. Interestingly, modulating the gut microbiome by rearing these flies under axenic conditions increased oxidative stress resistance of the more susceptible, but not the more resistant line, while it had no effect on starvation resistance for both lines. We also found that the stress-sensitive line had higher levels of Clostridiales bacteria and of the intracellular endosymbiont Wolbachia in the gut microbiota, as well as lower expression levels of immune effectors (antimicrobial peptides and lysozymes) in the head and gut. Both lines nevertheless showed similar susceptibility to pathogenic bacterial infections. In a transgenic Parkinson’s disease model, the stress-resistant background strongly attenuated the progressive locomotor defects induced by pan-neuronal expression of human mutant α-synuclein, but intriguingly not when α-synuclein expression was restricted to a subset of brain dopaminergic neurons in the protocerebral anterior medial (PAM) cluster. These results suggest that taking into account unapparent features of the reference lines could improve the reproducibility and consistency of neurodegenerative disease models in Drosophila
Non-conjugated TLR agonists increase the quantity of antibodies but not their quality in a murine immunization model
No full textInternational audienceBacterial vaccines have largely shifted from whole bacteria to selected proteins or glycans, thereby removing immune-stimulant components such as toll-like receptor (TLR) agonists from the formulation. Therefore, TLR agonists are often added to these vaccines to increase immunogenicity, and their addition has been frequently associated with increased antibody titers. To investigate the effects of TLR agonists at the B cell level, a small exploratory cohort study was performed with a murine immunization model using alum and R-phycoerythrin, with and without different TLR agonists. We observed that, while none of the TLR agonists increased affinity, the addition of TLR2, TLR9, and especially a combination of TLR2/4/9 agonists was able to increase the antibody quantity by increasing the number of secreting cells and/or cellular secretion rates. Our results indicate that the increased antibody titers for various TLR agonists or combinations might stem from an increased antibody magnitude rather than higher affinity antibodies