Fixed-term doctoral contract Study of acoustic spatio-temporal vortices for particle and cell manipulation M/F

Job Description

Thesis Subject

Project Context
Spatio-temporal vortices (STVs) constitute a cutting-edge class of structured wave fields. First introduced in optics about a decade ago, they have only recently been experimentally observed and analytically described in acoustics. These vortices correspond to acoustic beams carrying a phase singularity in the combined space–time domain. As a result, they possess an orbital angular momentum L whose direction is not necessarily aligned with the propagation axis and can be controlled through spatio-temporal structuring. This behavior contrasts strongly with conventional acoustic beams, for which L is aligned with the propagation direction. Some conventional acoustic beams allow elliptical particle motion and therefore generate an acoustic spin angular momentum S, a property formally analogous to the polarization of electromagnetic waves. STVs generally carry such a spin angular momentum S, whose orientation can be independently controlled. Owing to these angular momentum components, STVs offer unprecedented opportunities for particle manipulation. The transfer of L and S from the beam to irradiated particles induces motion through time-dependent radiation forces and torques, enabling particle dynamics that cannot be achieved with stationary beams. These additional degrees of freedom could open new possibilities for the manipulation of biological cells. In particular, differences in mechanical properties such as cellular rigidity could lead to distinct responses to the acoustic field, potentially enabling distinguishing between different cell types. However, as relatively complex polychromatic structured fields, STVs raise several analytical and experimental challenges. Most advanced theoretical descriptions of acoustic fields, their interactions with particles, and the associated conservation laws rely on the assumption of monochromatic fields. Consequently, a revision and extension of the theoretical framework are required. From the generation standpoint, designing sources capable of producing both space–time coupling and wide bandwidth remains particularly challenging. Another key difficulty lies in integrating such sources into a microfluidic environment where the particles are suspended.

Objectives
Within the framework of this PhD project, we aim to develop an analytical description, perform numerical optimization, and potentially achieve experimental observation of particle manipulation using acoustic STVs. By optimizing the field–particle interaction—particularly the induced torque—the required beam parameters will be identified, thereby revealing the characteristics needed for the generating system. The long-term objective is to enable the identification of cancer cells through observation of the induced torque.

Research Tasks
The majority of the research will be analytical and numerical. Three main theoretical tasks will be undertaken: (i) determining an appropriate analytical representation of the acoustic field, (ii) modeling the particle, taking into account the biological orientation of the project, (iii) describing the interaction between the acoustic beam and the particle. Subsequently, numerical optimization of the STV will be performed in order to maximize its manipulation capabilities and its ability to discriminate between different particles. In addition, there will be an exciting opportunity to contribute to the fabrication of the source and to participate in experimental measurements. We are therefore seeking a highly motivated candidate with a strong theoretical and numerical background in acoustics and microfluidics, who is interested in extending their expertise toward experimental implementation and the characterization of advanced acoustic wave fields, and who views experimentation as an essential complement to theoretical work.

Your Work Environment

The Institute of Electronics, Microelectronics and Nanotechnology (UMR CNRS 8520) is located in Villeneuve d'Ascq, near the city of Lille (France). With a total staff of over 500, the institute covers a wide range of research activities ranging from physics to materials science, acoustics, micro- and nanotechnology.

Funding: This contract is supported by the ANR JCJC STIMULE project (Spatio-temporally modulated inhomogeneous acoustic fields for probing the mechanical properties of biological particles).

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.

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