PhD: Acoustic streaming in biological porous media, IRPHé Marseille, 2026-2029

Background:Most biological tissues can be considered micrometer-scale porous media with either a hard (cortical bone) or soft (tumor) matrix. Numerous studies demonstrate the effect of ultrasound on biological mechanisms such as bone regeneration, neuromodulation, or the dissolution of blood clots. More recently, low-intensity ultrasound has been identified as capable of improving drug delivery to tumors.The underlying mechanisms involved in these effects remain poorly identified and poorly understood. One of the phenomena mentioned in the literature is acoustic streaming, a nonlinear hydrodynamic phenomenon producing fluid motion capable of generating fluid shear that triggers a biological response. This thesis project proposes to develop models (theoretical, experimental, and numerical) to study acoustic streaming in biomimetic porous media and its biological effects. StepsTo better understand the cascade of events defining these mechanotransductions, several approaches will be used:Experimental approach:IRPHé has a µPIV system coupled with an ultrasonic source (work by E. Ghiringhelli). This system has been used to characterize acoustic streaming in microfluidic channels with a rectangular cross-section.A first step would be to work on a single cylindrical pore fabricated at the LAAS-CNRS. This simple geometric shape (axisymmetry) would facilitate the development of analytical models (coll. S. Le Dizes, IRPHé) and numerical models (EF Comsol Multiphysics).The next step will involve preparing phantoms of soft (hydrogel) and hard (resin) porous tissues that are transparent (for optical access) and adapting the experimental setup (coll. P. Lasaygues LMA) to visualize the movement of fluorescent particles within these structures. Numerical approachIn parallel, the thesis project plans to develop a digital twin (EF Comsol Multiphysics) to estimate the shear stresses generated within porous scaffolds, which are representative of the mechanical stresses applied to cells in their in vivo microenvironment. Mechanical/Biological CorrelationThese results will be compared with in vitro experiments using cells (MLOY4 for bone regeneration and tumor spheroids/organotypic models for the treatment of brain cancers) in collaboration with the iBV (Nice) and the CRCM (Marseille). Key words: Mechanotransduction; acoustic streaming. porous media; µPIV