This study is part of the ANR CellDance project which explores a new approach combining nanophotonics and microfluidics to measure the mechanical response of individual cells for diagnostic purposes. Indeed, the deformability of individual cells is an indicator of certain diseases such as malaria. In this master project, we propose a first study on the mechanical measurement of gel beads whose mechanical properties mimic those of red blood cells.
We will use agarose gels to model the red blood cell (RBC). First, it is important to characterize their mechanical properties by AFM. Elasticity and viscoelasticity measurements will be proposed [1], to access the Young's modulus (E) or the dynamic moduli G' and G'' (Fig. 1), as a function of the frequency. Different geometries and AFM tips will be considered. Comparisons with red blood cells will be performed in order to find the best system describing the cell. For example, different concentrations of the gel constituents will be tested. Once the model has been defined, rheological modeling will be considered.
This study will continue in collaboration with our partners in Lyon (INL) with the aim of trapping objects optically on metasurfaces. We will consider some experiments on gel beads and red blood cells that deform when trapped near the surface. The resonance cavity created allows us to determine the reflectivity (Fig. 2) and thus to measure the deformation of the object (gel or red blood cell), thus having access to its rheology. We will then compare these two methods.
Figure 1. Rheological curves of a gel
Figure 2. Trapping of a deformable object on a metasurface

Candidate : We are looking for a candidate with interests in experimentation, who will interact with both teams. Mechanical/physical background. Highly motivated.

Continuation in thesis : possible and desired
References : [1] Y. Abidine, V.M. Laurent, R. Michel, A. Duperray, L.I. Palade, C. Verdier, Physical properties of polyacrylamide gels probed by AFM and rheology, Europhys. Letters, 109, 38003 (2015)
Mis à jour le 21 June 2022