arXiv subjects

Jacques Fattaccioli

Publications and source records attributed to Jacques Fattaccioli.

7 recordsLinked to original sources

arXiv2025

A Microfluidic Platform for Actin-Based Membrane Remodeling Reveals the Stabilizing Role of Branched Actin Networks on Lipid Microdomains

Cell shape changes, essential for processes such as motility or division, are controlled by the actomyosin cortex that actively remodels biological membranes. Their mechanisms can be deciphered in___vitro using biomimetic reconstituted systems, such as giant unilamellar vesicles (GUVs) with controlled lipid composition coupled to reconstituted actin networks. These assays allow mimicking cell shape changes in controlled biochemical and biophysical environments. However, studying the dynamics of these shape changes on statistically significant populations of GUVs with the possibility to sequentially modify the protein composition of the assay is a major experimental challenge. To address these issues, a microfluidic approach is used to immobilize several dozens of isolated GUVs and monitor membrane and actin network evolution. The loading of the chamber with GUVs and actin is first characterized. Then, the actin-induced remodeling of populations of homogeneous and phase-separated GUVs is monitored and shows that actin networks prevent the coalescence of lipid microdomains and that, in return, the number of domains affects the actin network structure. This microfluidic-based experimental strategy, thus, allows for studying actin-induced membrane deformation in___vitro and can be adapted to other studies on membrane remodeling processes.

cond-mat.soft↗

arXiv2025

Fully integrated automatic reusable microfluidic setup for immobilization, analysis and non-selective release of particles

We present a microfluidic device that enables trapping, analysis, and on-demand release of individual microparticles through membrane deformation driven by pneumatic actuation. Inspired by Pachinko-style architectures, the system features an array of traps supported by a deformable PDMS membrane, actuated via pressure control in a pneumatic chamber bonded above. Unlike conventional rigid designs, our configuration enhances membrane flexibility using a wide elliptical cavity and suspended rectilinear flow guides. Device characterization was performed using confocal microscopy to measure membrane deformation under controlled negative pressure. The displacement profiles obtained were compared to several theoretical models, showing strong agreement with a thick-membrane approximation. Vertical membrane displacement exceeded 120 $\mu$m under -100 mbar, allowing release of 80 $\mu$m particles. We demonstrated rapid and repeatable particle trapping and release by applying coordinated fluidic and pneumatic pressures. The system was further integrated with a Python-based control interface using $\mu$Manager libraries, enabling automated sequences of particle trapping, imaging, and release. The protocol includes automated priming to eliminate air bubbles in the microchannels. This work introduces a robust and fully automated microfluidic platform capable of reversible microparticle immobilization. It is well suited for applications such as high-throughput screening, mechanobiology, or real-time imaging workflows that require precise control over individual object handling.

physics.app-ph↗

arXiv2025

Assessing ultrasonic and optical flow velocimetry in a millifluidic device using oil-in-water emulsions as blood mimicking fluid

Blood-mimicking fluids (BMFs) play a critical role in ultrasonic imaging and Doppler flow studies by replicating the physical and acoustic properties of blood. This study introduces a novel soybean oil-in-water emulsion as a BMF with particle size and deformability akin to red blood cells. Using a millifluidic device, we cross-validated flow profiles through both Doppler velocimetry and optical particle tracking, demonstrating compatibility with theoretical Poiseuille flow models. The millifluidic chip, fabricated via stereolithography, provided an optimized platform for dual optical and ultrasonic assessments. Results showed strong agreement between the two methods across a range of flow rates, affirming the suitability of the emulsion for velocimetry applications. Furthermore, the acoustic properties of soybean oil droplets support their potential as an echogenic and stable alternative to conventional BMFs.

physics.med-ph↗

arXiv2024

Using lateral dispersion to optimise microfluidic trap array efficiency

Microfluidic trapping arrays have proven to be efficient tools for various applications that require working at the single-cell level, such as cell-cell communication or fusion. Although several hydrodynamic trapping devices have already been optimised, two-dimensional (2D) single-layer trapping arrays with high trap densities remain partially inefficient. Specifically, many traps remain empty, even after prolonged injection, which drastically reduces the number of samples available for post-treatment. These unfilled traps result from the symmetrical nature of the flow around the traps, and breaking this symmetry enhances capture efficiency. In this study, we use a numerical approachto show that optimal geometries can significantly increase filling efficiency and a preliminary experimental test confirming our approach is provided. We show that these improvements are achieved by promoting lateral dispersion of particles, facilitated either through an optimised oblique flow or by introducing disorder into the spatial arrangement of traps without specific inlet/outlet adjustment.

physics.flu-dyn↗

arXiv2021

Spanwise dispersion optimizes the efficiency of dense microfluidic trap arrays

Microfluidic Trap Arrays (MTAs) have proved efficient tools for several applications requiring working at the single cell level like cancer understanding and treatment or immune synapse research. Unfortunately, it generally appears that many traps stay empty, even after a long time of injection which can drastically reduce the number of samples available for post-treatment. It has been shown that these unfilled traps were due to the symmetrical nature of the flow around the traps, with a break in symmetry improving capture efficiency. In this work, we use a numerical approach to show that it is possible to generate optimal geometries that significantly improve capture efficiency. This efficiency is associated with an increase in the lateral dispersion of the objects; we show that adding disorder to the layout of the traps is the most optimal solution and may stay very efficient independently of the trap array size. These numerical results are corroborated by experiments, validating our approach.

physics.flu-dyn↗

arXiv2021

Enhancing the capture efficiency and homogeneity of single-layer flow-through trapping microfluidic devices using oblique hydrodynamic streams

With the aim to parallelize and monitor biological or biochemical phenomena, trapping and immobilization of objects such as particles, droplets or cells in microfluidic devices has been an intense area of research and engineering so far. Either being passive or active, these microfluidic devices are usually composed of arrays of elementary traps with various levels of sophistication. For a given array, it is important to have an efficient and fast immobilization of the highest number of objects, while optimizing the spatial homogeneity of the trapping over the whole chip. For passive devices, this has been achieved with two-layers structures, making the fabrication process more complex. In this work, we designed small microfluidic traps by single-layer direct laser writing into a photoresist, and we show that even in this simplest case, the orientation of the main flow of particles with respect to the traps have a drastic effect on the trapping efficiency and homogeneity. To better understand this phenomenon, we have considered two different flow geometries: parallel and oblique with respect to the traps array, and compared quantitatively the immobilization of particles with various sizes and densities. Using image analysis, we show that diagonal flows gives a spatial distribution of the trap loading that is more homogeneous over the whole chip as compared to the straight ones, and by performing FEM and trapping simulation, we propose a qualitative explanation of this phenomenon.

physics.flu-dyn↗

arXiv2016

Luminescent and absorptive metal-coated emulsions for micro-velocimetry

Fluorescent latex beads have been widely used as tracers in microfluidics over for the last decades. They have the advantages to be density matched with water and to be easily localizable using fluorescence microscopy. We have recently synthesized silver-coated oil droplets that are both luminescent and absorptive, by first coating the oil interface with a polydopamine layer and then depositing a silver layer by a redox process. They have a mean diameter of 6 \mu m and a their density has been matched to the density of water by adjusting the thickness of the metallic layer. In this work we used these particles as tracers to measure the velocity profile of a water flow in a PDMS microchannel with a rectangular cross-section, which allowed us to confirm the predictions of the Stokes equation with results comparable to those of common submicronic polystyrene particles.

physics.chem-ph↗