Description :
Context.
Microfluidic is the science and technology devoted to systems that process and/or manipulate small amounts of fluids (10^−9 to 10^−18 litres) within channels with dimensions of 10µm to 100µm [1, 2]. One of its essential applications concerns the fabrication of micrometric objects (so-called microparticles) via stretching and breakup of non-Newtonian fluids in a flow-focusing microchannel : a dispersed phase is stretched by a continuous phase leading to the dispersed phase breakup and then giving rise to microparticles. Depending on the flow parameters (phase velocities U1 and U2, and size of the channel L) and the rheological properties of the considered fluids (viscosity, elasticity, plasticity, surface tension etc.), the obtained objects can exhibit a variety of final shapes, from spherical mono or multiphase drops to filaments, passing through pearls, bowls, sombreros, bullet-like, capsules, and prolate microparticles [some of those shapes are shown in 3 and 4]. These objects can be subsequently used to encapsulate bioactive agents (such as drugs, proteins, and cells) in applications like drug delivery, cell culture, tissue engineering, and bioassays. Furthermore, they can also be employed as cell-mimicking microparticles with similar size, shape, deformability, and mechanical properties [3].

Problematic.
The fabrication of microparticles via microfluidics involves the stretching and subsequent breakup of elasto-viscoplastic fluids [complex materials that can behave either like an elastic solid or a viscous liquid, depending on the solicitation ; 5] at very high strain-rate levels (U/L ≈ 10^5 s-1), a fluid mechanics’ problem that remains unclear up to now. Lacking a priori fundamental physical understanding of such a problem, the control of the above applications is often done by trial-and-error [3], and consequently it is far from optimal.

Objective.
The current project aims to highlight the physical mechanism driving the formation of microparticles via stretching and breakup of elasto-viscoplastic fluids [5] in a microfluidic flow-focusing system. It will be conducted through a mixed approach by combining experiments and numerical simulations. The results will be analysed in light of filament stretching dynamics, energy transfer, and scaling laws [6, 7]. Finally, a good quantitative matching between experiments and numerical simulations would allow us to adequately describe the energy transfer during the stretching/breakup process and, thus, to precisely highlight the relevance of each rheological ingredient (viscosity, elasticity, plasticity, and surface tension) during the microparticles fabrication, as well as to predict their final shapes.

Participants.
We are seeking a highly motivated PhD researcher interested in developing a mixed experimental-numerical profile in Fluid Mechanics to join our project. The former will be developed at the CFL Research Group at CEMEF, Mines Paris PSL, which is ideally positioned to pursue this objective, as it gathers experts on numerical and experimental Fluid Mechanics. Furthermore, this research will be grounded on a strong collaboration with industrial and academic European partners.

Contacts.
Dr. Anselmo PEREIRA (anselmo.soeiro_pereira@minesparis.psl.eu), Dr Edith PEUVREL-DISDIER (edith.peuvrel-disdier@minesparis.psl.eu), and Prof. Elie HACHEM (elie.hachem@minesparis.psl.eu).

References
[1] G. M. WHITESIDES, Nature, 2006 | [2] P. TABELING, Oxford University Press, 2005 | [3] C. ZHANG et al., Biomaterials Research, 2021 | [4] Q. JI et al., Nature, 2018 | [5] P. SARAMITO - Journal of Non-Newtonian Fluid Mechanics, 2009 | [6] R. VALETTE et al., Journal of Non-Newtonian Fluid Mechanics, 2021 | [7] A. PEREIRA et al., Journal of Non-Newtonian Fluid Mechanics, 2022

Reference :

Date de démarrage : 03 septembre 2023

Durée :

Contacter :
Mines Paris, CEMEF
Dr. Anselmo PEREIRA (anselmo.soeiro_pereira@minesparis.psl.eu)
1, rue Claude Daunesse 06904 Sophia Antipolis cedex
email : anselmo.soeiro_pereira@minesparis.psl.eu