Simulating Microswimmers Under Confinement With Dissipative Particle (Hydro) Dynamics

C. Miguel Barriuso Gutiérrez1, José Martín-Roca1,2, Valentino Bianco2, Ignacio Pagonabarraga3,4,5 and Chantal Valeriani1,6*

1 Departamento de Estructura de la Materia, Física Térmica y Electrónica, Universidad Complutense de Madrid, Madrid, Spain 2 Departamento de Química Física, Facultad de Química, Universidad Complutense de Madrid, Madrid, Spain 3 Departament de Física de la Matèria Condesada, Facultat de Física, Universitat de Barcelona, Barcelona, Spain 4 Universitat de Barcelona Institute of Complex Systems, Barcelona, Spain 5 Centre Européen de Calcul Atomique et Moléculaire (CECAM), Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland 6 GISC—Grupo Interdisciplinar de Sistemas Complejos, Madrid, Spain

In our work we developed a functionality which enables simulation of self-propelled composite colloids of different shapes (or in general microswimmers) immersed in an explicit solvent composed of DPD particles, thus taking into account thermal fluctuations. The self-propulsion, inspired by the squirmer model, is achieved via force exchange between the colloid’s particles and their solvent neighbors, in such a way that linear and angular momenta are locally conserved at each step. The implementation is done via a custom ‘fix’ and also using the RIGID and MOLECULE packages and the DPD pair_style. The functionality is parallelizable and shows good time scaling with system size and number of cores (see figs. below) although the code still needs refactoring and polishing. In [1] you can find a more detailed description of the method and the results achieved for a active colloid (for three different squirmer propulsion mechanisms) and an active polymer, all of them both in bulk and in confinement inside a cylindrical channel. We analyze the solvent velocity flow fields, diffusion properties, orientation autocorrelation functions and radius of gyration for different types of microswimmers. Currently we are continuing the work studying suspensions of active colloids and the dynamics of an asymmetric colloid confined between parallel walls under gravity.

[1] Barriuso Gutiérrez, C. Miguel, José, Martín-Roca, Valentino, Bianco, Ignacio, Pagonabarraga, and Chantal, Valeriani. “Simulating Microswimmers Under Confinement With Dissipative Particle (Hydro) Dynamics”.Frontiers in Physics 10 (2022).