洛林大学PhD Position in colloids under an external field: a model system of activated matter申请条件要求-申请方
主办方
洛林大学
PhD直招介绍
Laboratory:
LCP-A2MC
Université de Lorraine
1 boulevard Arago, 57070 Metz
http://lcp-a2mc.univ-lorraine.fr/
PhD subject :
Colloidal particle assemblies have been the subject of increasing interest in recent years, not only for their various technological applications, but also because they reproduce phenomena described by condensed matter physics at an accessible experimental scale (length of the order of a micron, time of the order of a second). In addition, the possibility of varying inter-particle interactions makes it possible to control and test collective behaviors analogous to those encountered at the atomic scale. When colloidal particles have paramagnetic properties, it is possible to control their interactions using an external magnetic field: their structure and dynamics can then be characterized by optical microscopy as a function of the applied field, either static [Messina 2015, Spiteri 2018, Bécu 2017] or dynamic [Elismaili 2021a,b].
Figure 1: Sketch of the triaxial dynamic magnetic field setup (left) and the resulting paramagnetic colloidal assembly (right).
In this project, we propose to develop a model system of activated matter based on paramagnetic colloids. While active matter is held out of equilibrium by an energy source internal to its individual components, activated matter is held out of equilibrium by an external energy source. This energy source provides a much greater agitation of the particles than thermal agitation, giving rise to new physical properties. An example of activated matter are vibrated granular systems [D'Anna 2003], where grains placed on a vibrating table perform random jumps due to variable friction with the substrate, which allows to define an effective temperature of this activated system [Zamponi 2005]. In our case the random agitation of the colloids is generated by the dynamic magnetic field. The proposed system consists of a monolayer of short rods of colloidal beads (dimers or trimers) confined by gravity on a substrate (see figure in the attached PDF). The assembly of magnetic beads into rods is mastered in the laboratory, where we recently studied their dynamic behavior under an attractive rotating field [Hamid 2024].
When a magnetic field orthogonal to the plane of the monolayer is applied, the rods develop a dipole collinear with the field which tends to orient them along the field lines. A theoretical study on a dimer of unbound magnetic beads showed that as the intensity of the external magnetic field increases, 3 distinct states can be obtained: a horizontal state (dimers remain on the substrate), an intermediate inclined state and a vertical state (dimers perpendicular to the substrate) [Kemgang 2020]. The dipolar interactions are then essentially repulsive, and can be modulated by the orientation angle between the axis of the rod and the dipole moment. The first part of the thesis will focus on an investigation of the static structures of monolayers of rods subjected to a static or dynamic orthogonal field.
In a second part of the project, we will focus on binary systems with heterogeneous interactions. Experimentally, such a system can be made from a mixture of beads and rods placed in the same static repulsive field conditions. We will study the structural properties of this system, and we will compare the experiments with numerical simulations of molecular dynamics (LAMMPS). Using a local expertise developed over the past few years, numerical simulations will also provide access to the mechanical properties of these binary systems [Li 2020, Elismaili 2022].
In order to experimentally characterize the mechanical properties of the colloidal suspension, we will measure the deformations induced by flows in a microfluidic channel [Galambos 1998, Pipe 2009]. These channels will be manufactured using our laboratory's existing techniques with the collaboration of Mr. Jean-Pierre Gobeau, assistant engineer. Microfluidics is a suitable means to characterize the mechanical properties of the colloidal suspension for two reasons: on the one hand, colloids can be visualized under an optical microscope to follow their movement; on the other hand, the microfluidic chip can be inserted into the magnetic field setup in order to apply the external field during the experiment.
References:
[Spiteri 2018] L. Spiteri, R. Messina, D. Gonzalez-Rodriguez and L. Bécu, Ordering of sedimenting paramagnetic colloids in a monolayer, Phys. Rev. E. 98, 02061(R) (2018).
[Messina 2015] R. Messina, S. Al Jawhari, L. Bécu, J. Schockmel, G. Lumay and N. Vandewalle, Quantitatively mimicking wet colloidal suspensions with dry granular media, Sci. Rep. 5, 10348 (2015).
[Bécu 2017] L. Bécu, M. Basler, M. L. Kulic and I. M. Kulic, Resonant reshaping of colloidal clusters on a current carrying wire, Eur. Phys. J. E 40, 107 (2017).
[Elismaili 2021a] M. Elismaili, L. Bécu, H. Xu and D. Gonzalez-Rodriguez, Dissipative non-equilibrium dynamics of self-assembled paramagnetic colloidal clusters, Soft Matter 17, 3234 (2021).
[Elismaili 2021b] M. Elismaili, L. Bécu, H. Xu and D. Gonzalez-Rodriguez, Rotation dynamics and internal structure of self-assembled binary paramagnetic colloidal clusters, J. Chem. Phys. 155, 154902 (2021).
[D'Anna 2003] G. D’Anna, P. Mayor, A. Barrat, V. Loreto and F. Nori, Observing brownian motion in vibration- fluidized granular matter, Nature 424, 909 (2003).
[Zamponi 2005] F. Zamponi, F. Bonetto, L. F. Cugliandolo and J. Kurchan, A fluctuation theorem for non-equilibrium relaxational systems driven by external forces, J. Stat. Mech.: Theory Exp., 2005, P09013 (2005).
[Hamid 2024] A. H. Hamid, D. Gonzalez-Rodriguez, H. Xu and L. Bécu, Dynamics of paramagnetic permanent chains and self-assembled clusters under a rapidly rotating magnetic field, J. Chem. Phys. 161, 164905 (2024).
[Kemgang 2020] E. Kemgang, H. Mohrbach and R. Messina, Magnetic dimer at a surface: Influence of gravity and external magnetic fields, Eur. Phys. J. E 43, 46 (2020).
[Elismaili 2022] M. Elismaili, D. Gonzalez-Rodriguez and H. Xu, Activity-modulated phase transition in a two-dimensional mixture of active and passive colloids, Eur. Phys. J. E 45, 86 (2022).
[Galambos 1998] P. Galambos and F. Foster, An optical micro-fluidic viscometer, ASME International Mechanical Engineering Congress and Exposition, Vol. 15960, pp. 187-191. American Society of Mechanical Engineers, 1998.
[Pipe 2009] C. Pipe and G. H. McKinley, Microfluidic rheometry, Mechanics Research Communications, Vol. 36, pp. 110-120, 2009.
洛林大学Phd申请条件和要求都有哪些？PhD Position in colloids under an external field: a model system of activated matter项目是不是全奖？有没有奖学金？下面我们一起看一下洛林大学申请Phd直招需要具备哪些条件和要求，以及托福、雅思语言成绩要到多少才能申请。
申请要求
Candidate: Physicist or engineer motivated to work on the thesis subject. The candidate will be attracted to experimental work and have programming skills as well. A B2 level of English is required. Knowledge of French is useful but not required.
报名方式
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招生人信息
Admissions Officer
David Gonzalez-Rodriguez david.gr@univ-lorraine.fr
Lydiane Bécu lydiane.becu@univ-lorraine.fr
Hong Xu hong.xu@univ-lorraine.fr
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