NWARPS : Nucleation, Wetting, Adhesion, and Rheology of Polymeric Surfaces
Description of the PhD project
The Folding Sliding Stretching Lab is seeking a PhD candidate to elucidate the microscopic mechanisms at play on soft interfaces to design smart materials for a sustainable future. This project is driven by the need for surfaces capable of efficiently harvesting dew—a vital resource in arid environments—and advancing thermal management and anti-icing technologies. Candidates can also engage in related projects, such as studying granular materials rendered cohesive by polymer coatings to produce “reversible” concrete. Crucially, the fundamental physics governing water condensation and droplet depinning on these soft interfaces extend far beyond dew harvesting. The underlying mechanisms—specifically heterogeneous nucleation and contact line dynamics—share profound analogies with fluid transport and precipitation processes essential for next-generation building materials. By understanding how polymer architectures control capillary trapping and phase transitions at the microscale, this project will provide critical physical insights to optimize CO2 mineralization and fluid dynamics within both carbon-capturing and reversible concrete.
When moist air contacts a cold surface, it forms a breath figure composed of numerous small droplets, with nucleation occurring heterogeneously at discrete sites or homogeneously, depending on the substrate. While traditional studies on rigid substrates have established universal scaling laws for droplet size distributions, polymer-coated surfaces introduce complexities that remain poorly understood, but offer the promise of controlling nucleation. To harvest dew, drops must be evacuated by sliding over the surface. Here, polymers or microscopic heterogeneities significantly modify drop motion to control dynamics—facilitating sliding or pinning. Both droplet nucleation and contact line depinning are similar, as their underlying physical description relies on thermal hopping over energy barriers.
The team and their collaborators at the University of Twente have made initial studies in both soft-nucleation [DOI:10.1103/PhysRevLett.134.188204] and the dynamics of a drop [DOI:10.1038/ncomms12545]. Candidates are invited to elaborate one or both of these questions in their thesis proposal, or present related situations of polymers at interfaces, where they govern critical physical phenomena such as wetting, nucleation, adhesion, and rheology. The thesis will pair a significant experimental component with analytical modelling and/or numerical simulation.
A new setup to study vapor transport via diffusion or convection will improve upon a system currently at the University of Twente. This allows studying mechanical coupling between substrate elasticity and droplet density by varying the polymer architecture – from elastomers, to gels and networks with dangling ends, and the transition from nanoscale nucleation to macroscopic droplets via AFM or ellipsometry.
The depinning transition and the role of thermal activation on drop motion are active research topics, though experimental access to contact line thermal motion is difficult. To drive drop motion, we propose shaking the liquid surface with the spectral density of Brownian noise, creating artificial “thermal” fluctuations at optical scales. Since these fluctuations can be observed, this provides an ideal system to address how depinning happens at the scale of fluctuations.
Keywords
Soft matter, polymer, wetting, nucleation, thermal activation, dew harvesting
Research Unit, UMR number and acronym
ENS - Laboratoire de Physique de l’Ecole Normale Supérieure, UMR 8023 LPENS
Description of the research Unit/subunit
The Folding Sliding Stretching Lab is located at the Ecole Normale Supérieure in the heart of Paris’ Latin Quarter. Our research themes are fluid and solid mechanics in conjunction with other disciplines : non-linear physics, out-of-equilibrium statistical physics, geomorphology and planetology. We use a combination of laboratory experiments, theory and numerical simulations. The group activity is fundamental in nature and collaborations with industry, geophysicists and with the medical field give it a taste of applied science.
The candidate will have access to the research support infrastructure at the ENS Physics Department including a class-10000 cleanroom and microfabrication facility, in-house mechanical workshop and engineering design office, and their full-time support staff. Equipment such as an AFM and a Phase Doppler Interferometer (aerosol droplet sizing) may be useful for the proposed thesis and already exist in the group.
Name of the supervisor
Bruno Andreotti (Bruno.Andreotti@phys.ens.fr)
Name of the co-supervisor
Kristina Davitt (Kristina.Davitt@phys.ens.fr)
3i Aspects of the proposal
Intersectoriality
The research division of the French multinational Saint-Gobain is a natural industrial partner for this project and we will support the candidate to make a connection to them during the thesis.
International
The team has a longstanding collaboration with Pr. Snoeijer at the University of Twente, including the preliminary study of breath figures, which is relevant for the proposed thesis. He is a leading expert in (soft) wetting dynamics and is working on the development of predictive models for nucleation on polymeric surfaces, a core challenge in this project. It is therefore natural that the candidate spends a period of time at Pr. Snoeijer’s lab.
Interdisciplinarity
The theme of soft-condensation sits at the frontier between physics and chemistry. For example, it is necessary to be able to model and account for diffusion, convection and degree of supersaturation in the environment. Statistical physics underpins the description of the nucleation and growth of drops as well as the thermally-activated motion of the contact line. In the case of soft substrates, polymer architecture at the surface is known to play a role, so an understanding of the nature of polymers at the microscopic scale is important, for instance, to determine the role of vapor permeation in the polymer network, or if condensation nuclei or contact-line pinning centers correspond to free chains or other local heterogeneities.
Expected profile of the candidate
The candidate should hold a degree in physics, chemistry or closely related sub-discipline. They do not need to have prior expertise in both the physical and chemical aspects of the problem, but should have a strong interest in fundamental research and interdisciplinarity with a desire to participate in experiments. Prior experience in a laboratory setting is highly appreciated, as well as a comfort with programming for data analysis.
Proficiency in scientific English is obligatory and the candidate must be able to communicate in a professional environment, be able to write clearly and speak in front of an audience of scientists. The Proficiency in scientific English is obligatory and the candidate must be able to communicate in a professional environment, be able to write clearly and speak in front of an audience of scientists. The candidate is expected to be curious about the scientific problem they propose to work on, show personal initiative, and to be able to work independently, with scientific rigor.
Important dates
Call for applications : from September 1st to October 31st 2026
Eligibility check results : November
3i Committee evaluation results : December
Interviews from the shortlisted candidates with the Selection Committee : January 2027
Start of the PhD : March 1st 2027