CDD Doctorant: Microfluidique methods for the analysis of aerosol ice nucleating properties (M/F)

Job Description

Thesis Subject

The oceans cover more than two-thirds of the Earth's surface and dominate the Southern Hemisphere. As a result, the marine atmosphere plays a central role in the Earth's climate system. Marine aerosols are emitted through wave breaking and bubble bursting at the air–sea interface, producing sea spray aerosols (SSA) that can remain suspended in the atmosphere for several days. These particles influence climate both directly, through interactions with solar radiation, and indirectly, by acting as cloud condensation nuclei (CCN) and ice-nucleating particles (INPs). The phase of clouds (liquid, mixed-phase, or ice) strongly influences their radiative properties, lifetime, and precipitation efficiency. However, ice formation through heterogeneous nucleation remains one of the largest uncertainties in climate models. This uncertainty is particularly important at relatively warm temperatures (0 to –20 °C), where INP concentrations are extremely low and difficult to measure. Improving our understanding of INP sources and variability in this temperature range is essential for reducing uncertainties in the representation of mixed-phase clouds, especially over the Southern Ocean, a region that exerts a strong influence on the global climate system.

Current measurement techniques suffer from significant limitations. Online instruments are generally restricted to temperatures below –20 °C, while offline approaches require sample collection, storage, and transport, which can introduce substantial artefacts. This PhD project aims to investigate the links between marine biogeochemistry and the production of ice-nucleating particles in the Southern Ocean.

To achieve this goal, the project will involve the finalization of the development and deployment of a novel online ice nucleation instrument based on microfluidic technologies, automated optical detection, and precise temperature control (0 to –35 °C). This miniaturized and portable system will enable real-time quantification of ice-nucleating particles in seawater and, ultimately, in marine aerosols generated aboard research vessels. With the objective to deploy this instrument directly aboard research vessels during the 2028 Southern Ocean campaigns (ASOLAS and the Antarctic-InSYNC initiative) to investigate the transfer of INPs from the ocean to the atmosphere and their role in the formation of ice crystals in marine clouds.

This doctoral thesis will be focused on two components.

The first component of the project will focus on the finalization, validation, and optimization of the prototype. This may include the design of future system developments but will primarily involve the characterization of the microfluidic system prototype and the development of automated image-processing algorithms. This work will result in a methodological reference publication. Regarding instrumental development, our objective is to explore how additional variables can be measured using microfluidic devices, either through the functionalization of the microfluidic chip or through the integration of complementary detection methods (e.g., fluorescence), in order to better characterize the contribution of biological compounds to the observed ice-nucleating properties. This work will also lead to methodological reference publication.

The second component will consist of applying this instrument to the study of samples collected during oceanographic campaigns in the Southern Ocean from 2027 onwards, particularly within the framework of the MISO2 program (R/V Investigator, South Pacific Ocean). The objective will be to collect seawater samples to evaluate the microfluidic technique in the laboratory alongside existing methods, and to obtain a first identification of the biogeochemical factors controlling the presence of ice-nucleating particles (INPs) in seawater and their spatial variability. In the longer term, the ambition is to deploy the instrument directly aboard research vessels during the 2028 field campaigns (ASOLAS, R/V Polarstern in the Weddell Sea, Antarctic-InSYNC initiative) in order to investigate the unique characteristics of the Southern and Polar Oceans during the austral winter.

Scientific Questions (INSU)
• How do marine biogeochemical processes influence the abundance and properties of ice-nucleating particles in seawater?
• What mechanisms control the transfer of marine INPs from the ocean surface to the atmosphere?
• What role do marine-derived INPs play in the formation of mixed-phase and ice clouds over the Southern Ocean?
Technological Questions (INSIS)
• How can microfluidic technologies be adapted for autonomous atmospheric measurements in remote environments?
• How can ice nucleation events be automatically detected and characterized in extremely small sample volumes?
• Can these technologies be extended to characterize other environmentally relevant properties related to climate, aerosols, or marine ecosystems?

Expected qualifications for the PhD candidate:
• This project has a strong experimental component and will be particularly well suited to candidates interested in instrument development, environmental measurements, and the deployment of novel sensors during field campaigns in challenging environments.
• Ideally, candidates should have a background in engineering (mechanical engineering, electronics/instrumentation, thermal engineering, microtechnology, etc.).
• Experience or skills in microfluidics and microfabrication would be considered an asset.

Your Work Environment

The PhD candidate will be based at the Laboratoire de Météorologie Physique (LaMP), a joint research unit (UMR 6016, CNRS – Université Clermont Auvergne) located on the Cézeaux campus in Aubière, near Clermont-Ferrand, France. The laboratory comprises approximately 100 permanent staff members, including researchers, faculty members, engineers, technicians, and administrative personnel, as well as numerous PhD students, postdoctoral researchers, and undergraduate and Master's interns. Research at LaMP focuses on atmospheric physics and chemistry, aerosol–cloud–climate interactions, atmospheric remote sensing, and surface–atmosphere exchanges.

The successful candidate will join the research team specializing in the physical and chemical properties of atmospheric aerosols and their interactions with clouds. The PhD project will be supervised by Dr. Evelyn Freney and Dr. Karine Sellegri.

The project will be co-supervised with the FEMTO-ST Institute (Besançon, France), which specializes in microfluidic technologies, under the guidance of Dr. Jean-François Manceau and Dr. Frank Chollet. The PhD candidate will undertake regular research stays in Besançon to receive training in microfluidic technologies, the design and fabrication of microfluidic devices, and the development of new microfluidic chips tailored to the objectives of the project.

Constraints and risks

No specific occupational hazards have been identified beyond those associated with computer-based work, the routine use of laboratory equipment, and standard laboratory safety procedures.

Compensation and benefits

Compensation

2300 € gross monthly

Annual leave and RTT

44 jours

Remote Working practice and compensation

Pratique et indemnisation du TT

Transport

Prise en charge à 75% du coût et forfait mobilité durable jusqu’à 300€

About the offer

About the CNRS

The CNRS is a major player in fundamental research on a global scale. The CNRS is the only French organization active in all scientific fields. Its unique position as a multi-specialist allows it to bring together different disciplines to address the most important challenges of the contemporary world, in connection with the actors of change.

CNRS

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