François Peaudecerf

Junior Professor Chair UR

Photo de François Peaudecerf

Email : francois [dot] peaudecerf [at] univ-rennes [dot] fr

Phone : +33 223233474

Office number : BAT 11A - room 140

Quick introduction

My main research interests lie at the interface between soft matter physics, fluid mechanics, biophysics, and environmental microbiology.

Current work of my lab combines experiments – using tools such as microfluidics and microscopy – and theoretical models to understand microbial dynamics in the environment and their macroscopic impacts. One question we are paricularly keen to explore within the interdisciplinary community of OSUR is how microbes such as bacteria interact with air-water interfaces in the soil and modify water dynamics there.

I always welcome informal enquiries from interested interns, PhD students, or post-doctoral researchers, so do not hesitate to francois [dot] peaudecerfatuniv-rennes [dot] fr (get in touch) !

After a BSc at École Polytechnique, I did my PhD at the University of Cambridge in the Department of Applied Mathematics and Theoretical Physics, under the supervision of Prof. Raymond E. Goldstein. I then went to ETH Zürich as a post-doctoral researcher and Marie Skłodowska-Curie fellow in the Environmental Microfluidics group led by Prof. Roman Stocker. I then moved to the IPR for my current Junior Professor Chair position.

News

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New OSUR Transverse Research Axis

8 January 2024

We created a new Transverse Research Axis entitled "Interactions Micro-organismes Environnement" within the framework of OSUR. The aim of the new TRA is to support interdisciplinary projects combining physics, geosciences and microbiology in order to deepen our understanding of microbial impacts on large scale environmental cycles. It will further strengthen the existing dynamic among OSUR members, with monthly internal seminars across participating research institutes to share ideas, approaches and methods. I will join the official organizing committee as the representative of IPR, together with Julien Farasin (OSUR), Achim Quaiser (ECOBIO) and Tanguy Le Borgne (Géosciences Rennes).

Portrait Nathan Chapelle and logo Region Bretagne
Nathan Chapelle starts his PhD!

1 October 2023

We are excited to share that Nathan Chapelle joined the Peaudecerf lab to start his PhD. His PhD project, funded by Région Bretagne via an "Allocation de Recherche Doctorale" (ARED BactEauS), will investigate the impact of surfactant producing bacteria on drying soil, with an initial focus on microfluidic model systems mimicking single soil pores. I will co-supervise Nathan together with Isabelle Cantat . Welcome Nathan!

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Alexandra Pucheu's work on bacteria-driven capillary rise

28 Juin 2023

We had the great pleasure to host Alexandra Pucheu for her MSc internship in Microbiology this spring, working on a project funder by OSUR (AO Blanc 2023), in collaboration with Dr. Cécile Monard and Dr. Tanguy Le Borgne. Alexandra did a great job establishing bacterial cultures in the lab, and designed a microfluidic device in which bacteria can trigger capillary rise as they grow and release surfactants in the surrounding medium. In future projects we aim to harness this mechanism as a novel technique to detect and isolate surfactant-producing soil bacteria. Thank you Alexandra!

Sketch of a plastron under flow with adsorbed surfactants at its surface
New paper on superhydrophobic surfaces out in PNAS

12th January 2023

With my long term collaborators Prof. Paolo Luzzatto-Fegiz, Dr. Julien Landel, Dr. Fernando Temprano-Coleto and others, we published a new model of flows over superhydrophobic surfaces in the presence of contaminating surfactants. Validating the model with experiments and simulations, we identify the mobilisation length, a new lengthscale of the problem to guide future experiments. Check the paper here. Illustration from Temprano-Coleto et al. 2023, CC BY 4.0

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A new start

1st December 2022

It is with great excitement that I am starting my new position as a tenure-track assistant professor ("Chaire Professeur Junior") at the Physics Institute of Rennes (IPR), University of Rennes . My lab will investigate bacterial impacts on the dynamics of air-water interfaces in the soil, trying to shed light on soil drying in a changing climate. I'm looking forward to collaborating with my new colleagues from the Soft Matter and Divided Media Departments.

Older news

Older news can be found in my former webpage .

Some on-going research topics

Coupling between microbes and interfaces in porous with varying water content

Bacteria abound in natural unsaturated porous environments, contributing to major global geocycles. Within these environments they live in capillary films, and by releasing surface active compounds alter interfacial forces in their immediate vicinity. While microscale air−water interface behavior is known to control large scale dynamics of water in a porous such as soil, it remains unclear how bacterial activity modifies these dynamics. Reciprocally, little is known on how the resulting 'waterscape' influences bacterial ecology (e.g. their dispersal). We approach the coupled dynamics of bacteria and air−water interfaces in porous media from different angles, starting from model systems such as single capillaries with isolated interfaces, then expanding to more complex model systems in microfluidics, and ultimately model soil columns. The goal is to characterise how bacterial behavior modifies the air−water interface properties and thus their dynamics in soil, to further elucidate how microbial forces can shape soil water dynamics in the environment.

Sketch of microscale processes in soil, such as drying, on which bacterial production of surface active compounds could have an effect. At the microscale, bacterial production of surface active compounds could modify the dynamics of air-water interfaces in soil during processes such as drying, imbibition and draining by roots. © François Peaudecerf

Behavioral adaptations of the microbial community in the sea surface microlayer

The aquatic microlayer consists of the upper ~500 micrometer depth of ponds, lakes, and oceans, and is characterized by strong exposure to UV, gradients in temperature and specific physico-chemical properties. It is a fascinating micro-environment to study as it represents the interface between water and air; buoyant material in the water collects there, and atmospheric material is deposited there. The microbial and planktonic community in the microlayer may thus play a crucial role in biogeochemical cycling via their impact on the properties of the microlayer. Despite this, very little is known about how the microbial community of the microlayer arises, and how bacteria and plankton live and move in this extreme environment. In collaboration with Dr. Jeanette Wheeler from Memorial University (Newfoundland, Canada), we are addressing these basic questions by directly observing microbial behavior in the microlayer.

Sketch of the sea surface microlayer, the bacteria swimming in it and aerosols being deposited at its surface. © François Peaudecerf

Drag reduction of superhydrophobic surfaces in presence of surfactants

Superhydrophobic surfaces (SHSs) trap microscale air-water interfaces, called plastrons, with the potential to significantly reduce drag due to flow. However, previous experimental work found inconsistent drag reduction. With Prof. Paolo Luzzatto-Fegiz and Dr. Julien Landel, we performed carefully controlled microfluidic experiments to evaluate the flow profile in the layer of a few microns below the plastron (using microscale particle imaging velocimetry or microPIV), revealing that the air-water interface was behaving more like a solid surface than the theoretical free-slip interface. Numerical simulations showed that this result could be explained by the presence of traces of surfactants - unavoidable in normal lab conditions - accumulating at the end of a plastron and thus generating Marangoni forces opposing flow. Since our initial publication on this topic, we further explored the modelling of these processes, in 2D and in 3D, but also investigate the coupling between surfactants, flow and geometry as happens when depositing surfactants on an interface shaped as a maze.

Pictures of an open water maze, in which a dyed solution of surfactant advances by Marangoni effect.

Marangoni flows – from local deposition of soap in a pool of red dye to visualise the resulting fluid motion – drive an interfacial flow toward the exit of a complex maze. The large clean interface at the exit of the maze preserves a strong surfactant gradient, which dead-ends cannot maintain. Illustration adapted from Temprano-Coleto et al., Soap opera in the maze: Geometry matters in Marangoni flows. Physical Review Fluids, 2018, CC BY 4.0.

List of publications