ESPCI web site
ESPCI Paris is a major institution of higher education (a French "Grande École d’ingénieurs"), an internationally renowned research center (17 laboratories), and a fertile ground of innovation for industry.
Using photo-lithography on demand and in situ on microfluidic chips became a breeding ground for high-throughput production of novel, confined gel structures in recent years.
Several examples include mono- or poly-disperse collections of soft discs, high-aspect-ratio rods and long ribbon-like structures.
These structures have been implicated in model 2D granular packings, novel and microscale flow-rate measuring protocols, and self-assembled units for next-generation materials.
Such microfluidic objects are often created using a photochemistry popularized by Doyle and co-workers, based on poly(ethylene glycol)-diacrylate and an appropriate photoinitiator. Interestingly, the structures’ mechanical properties can be tuned through a variation in crosslinking density, dilution or photoreticulation dosage.
Properly assessing the mechanical properties of these microscopic objects as a function of their size and environment remains a challenge, even while such properties control their response to micromechanical solicitation. Indeed, the challenge lies in the fact that their typical dimensions are micrometric, preventing the use of classical rheometry, for example.
Recently, some microfluidic techniques were developed respecting the constraints due to the microscopic particle size. These techniques are used to investigate elastic properties at long times only, and partially lack validation
against direct mechanical testing.
Furthermore, the materials produced may in fact be poro-elastic, displaying characteristic relaxation times and complex behavior under time dependent solicitation. The development of novel particulate model systems, well controlled micro-actuators or flexible hydrogel microchannels is hindered by the lack of a full characterization and control of the mechanical hydrogel properties.
The aim of our project is thus to fill this gap and to provide detailed mechanical characterization of these promising materials, combining direct measurements using atomic force microscopy (AFM) and indirect, on-chip optical characterization with spatio-temporal resolution.
This postdoctoral project is a collaboration between two ESPCI researchers whose expertise in : near-surface polymer physics, elastohydrodynamics and near-surface microscopy (JDM) ; and complex fluids, rheology, active fluids, suspension flow and microparticle fabrication (AL) ; are highly complementary.
The work will take place in the Gulliver and PMMH labs and in the Pierre-Gilles de Gennes Institute for Microfluidics, in the heart of Paris.
Recent or upcoming PhD graduates with high motivation and experience in some of the following topics are strongly encouraged to apply : soft condensed matter, hydrodynamics, self-assembly, atomic force microscopy and microfluidics.
For the application, we request a short motivation letter along with CV to job-ref-fcqyyg8hl@emploi.beetween.com.
and anke.lindner@espci.fr or joshua.mcgraw@espci.fr
12-month (renewable) post-doctoral position
Start date : 01/2024