Florent Malloggi

Selective and efficient purification methods are needed to recover metals from wastes with highly variable and complex compositions, such as printed circuit boards (PCBs). Fast process development is a key requirement for their development due to the rapid variability in waste composition and target metal content from one batch to another. Here, we report an easy‐to‐replicate integrated microfluidic platform enabling rapid process development, exemplified in the case of a nanosheet‐based highly silver‐selective membrane. The system combines controlled microfluidic injection, a tangential‐flow membrane module, and inline commercial X‐ray fluorescence detection within a unified architecture, allowing real‐time quantification of metal ion transport under precisely regulated flow conditions. Using a membrane incorporating phosphatoantimonic acid (H ₃ Sb ₃ P ₂ O ₁₄ ), we demonstrate preferential silver transfer from nitric‐acid leachates of real silver‐rich waste electronic components. The platform enables accurate and inline permeation monitoring while drastically reducing reagent consumption and experimental time compared with conventional batch methods. Moreover, machine learning allowed predicting silver concentrations with good generalization ability to unknown flow rates, which constitutes an additional step toward autonomous process optimization. Overall, this second generation of microfluidic platforms provides an efficient tool for fast process development, accelerated material screening, and optimization of environmentally beneficial recycling pathways.

Understanding crystallization from solution is essential to natural and industrial processes. In contrast to the mechanism envisioned in classical nucleation theory, crystallization from solution frequently proceeds after liquid–liquid phase separation (LLPS) into transient reactant-rich liquid structures that subsequently convert into amorphous solids and crystals. Whether this initial LLPS occurs by nucleation or spinodal decomposition under given conditions is crucial since the two pathways set different physical environments for subsequent crystal nucleation. Existing data, from proteins and inorganic species, cannot discriminate between these mechanisms: submillisecond nanoscale characterization has remained beyond reach, so measurements could capture only late-stage coarsening, and mechanistic conclusions rest on thermodynamic inference from the phase diagram. Here, we capture reactant-rich liquid structures of cerium oxalate as they emerge, using small-angle X-ray scattering coupled to a microfluidic ultrafast mixer, achieving nanometer spatial resolution at reaction times as short as 200 μs. We show by direct structural characterization that under our conditions, these liquid structures form by spinodal decomposition: diffuse concentration fluctuations develop without induction time, precluding nucleation. Unexpectedly, coarsening dynamics reveals that the transient structures are viscoelastic, i.e., viscous at time scales of second, but elastic at the shorter time scales relevant to crystal nucleation. This viscoelasticity, contrary to nonclassical multistep crystallization theories where the transient matrix is described as a classical viscous liquid, governs coarsening dynamics and crystal nucleation within it. Viscoelastic spinodal decomposition requires a large viscosity contrast between coexisting phases, a condition met, or expected, in other systems, suggesting such effects may be widespread in crystallization.

The mixing efficiency of five micromixer geometries, such as Butterfly, Baffle, Stretch–Split–Recombine, Staggered Herringbone Mixer, and Serpentine micromixer, is assessed using computational fluid dynamics (CFD) over a Reynolds‐number ( Re ) range from 1 to 180. Additional dye tracer experiments, using confocal microscopy, validate the CFD findings in the case of the Serpentine mixer, considering two homothetic sizes (100 × 100 and 200 × 200 µm) and Re  = 50 and 180. Although all micromixers achieve high mixing efficiencies, their characteristic mixing times span more than four orders of magnitude (0.249 ms to 2.82 s), depending strongly on geometry and flow regime. This wide dynamic range indicates that mixing performance is governed not only by Reynolds number but by the underlying transport mechanism vortex‐driven convection versus topological stretching and reorientation. Geometries based on systematic splitting and chaotic advection maintain short mixing lengths even at high Péclet numbers, whereas residence time depends on absolute geometric scale and operating flow rate. The results show that mixer selection should be guided not only by Reynolds number but by the desired mixing time, flow rate, pressure constraints, and fabrication complexity. These findings provide practical design guidelines and a scalable framework for micromixer selection in continuous‐flow synthesis.

The filtration membranes are often elaborated through a phase separation process where a polymer rich phase and a polymer poor phase spontaneously form through spinodal decomposition. One process that is still not well understood from a theoretical point of view is the non-solvent induced phase separation, where a thermodynamically stable film of a polymer mixture is put in contact with a bad solvent of the polymer. The invasion of the film by this non-solvent drives the film out of stability and leads to spinodal decomposition. During this phase separation, polymer poor and polymer rich regions form. In this article, we present a numerical study of the effect of kinetic coefficients, namely, the relative mobilities of polymer and solvent/non-solvent, on the observed patterns. Using 2D numerical simulations of the ternary Cahn–Hilliard model, we show that, for a given thermodynamic landscape, this parameter has dramatic effects: depending on its value, phase separation may or may not occur. We also show that it can affect the nature of the resulting pattern. In addition to analyzing 3D simulations, we characterize the final pattern using a quantitative indicator of connectivity and show that, for a wide range of initial compositions of the film, the final pattern is bicontinuous. Finally, we also quantify the transport properties of both polymer rich and polymer poor domains.

We review the application of micro- and milli-fluidic devices for in situ X-ray scattering, spectroscopy, and imaging in the physical sciences. In particular, we highlight the potential of analysis using commercial laboratory X-ray sources.

This study compares the mobility behaviour, in a H₂O₂ environment, of three different geometries of hybrid particle made of silica core functionalized by gold (nanoparticles or layer). It is known that the decomposition of H₂O₂ on gold surfaces drives mobility; however, the link between mobility orientation and the organization of gold on silica surfaces is still questionable. While conventional wisdom posits that asymmetric designs are crucial for generating phoretic forces or localized bubble propulsion, recent research suggests that symmetrical particles may also exhibit motility. To address this debate, we developed a robust workflow for synthesizing gold grafted silica nanoparticles with precise control over size and shape, enabling the direct comparison of their motile behaviour by dynamic light scattering and particle tracking velocimetry. Our results indicate, first, that a combination of techniques is necessary to overcome their intrinsic limitation and, second, that the inherent asymmetry generated by isotropic gold nanoparticle deposition onto silica surfaces may enable particle motility.

This study investigates the necessity of particle asymmetry for self-propulsion in nanomotors. While conventional wisdom posits that asymmetric designs are crucial for generating phoretic forces or localized bubble propulsion, recent research suggests that symmetrical particles may also exhibit motility. To address this debate, we developed a robust workflow for synthesizing gold grafted silica nanoparticles with precise control over size and shape, enabling the direct comparison of their motile behavior by dynamic light scattering and particle tracking velocimetry. Our results indicate that the inherent asymmetry generated during isotropic gold nanoparticle deposition onto silica surfaces may enable particle motility.

A heterogeneous photocatalyst was assembled through electrostatic immobilization of a cationic porphyrin at the surface of functionalized carbon nanotubes. The supra‐molecular nanohybrid catalyst was valorized in the aerobic photo‐oxidation of sulfides to the corresponding sulfoxides. The process operated selectively under visible light, with low catalytic loading, in water as the solvent, and the catalyst was readily recycled and reused.

Titanium dioxide nanoparticles were combined with carbon nanotubes and gold to develop improved photocatalysts for the production of hydrogen from water. The entangled nature of the nanotubes allowed for the integration of the photoactive hybrid catalyst, as a packed-bed, in a microfluidic photoreactor, and the chips were studied in the photocatalyzed continuous flow production of hydrogen. The combination of titanium dioxide with carbon nanotubes and gold significantly improved hydrogen production due to a synergistic effect between the multi-component system and the stabilization of the active catalytic species. The titanium dioxide/carbon nanotubes/gold system permitted a 2.5-fold increase in hydrogen production, compared to that of titanium dioxide/carbon nanotubes, and a 20-fold increase, compared to that of titanium dioxide.

The development of rapid, sensitive, portable and inexpensive early diagnostic techniques is a real challenge in the fields of health, defense and in the environment. The current global pandemic has also shown the need for such tests. The World Health Organization has defined ASSURED criteria (affordable, sensitive, specific, user-friendly, rapid and robust, equipment-free and deliverable to end-users) that field diagnostic tests must fulfill, which proves the real need in terms of public health. Giant magnetoresistance (GMR) sensors, which have flourished in a wide variety of spintronic applications (automobile industry, Information Technology, etc.), also have real potential in the field of health, particularly for the development of early diagnostic point-of-care devices. This work presents a new type of innovative biochip, consisting of GMR sensors arranged on both sides of a microfluidic channel which allow on the one hand to count magnetic objects one by one but also to better distinguish false positives (aggregates of beads, etc.) from labelled biological targets of interest by determining their magnetic moment. We present the operating principle of this new tool and its great potential as a versatile diagnostic test.