09:05 - 09:25

Stéphane Douady

Reconnections in mud and jellies

Université Paris Cité

In two-dimensional mechanics, it is common that cracks appear, and reconnect at right angles. However, some new experiments shows that cracks can run parallel without reconnecting, which can be ascribed as the formation being restricted to one dimension. But even in the two-dimensional case, one crack can avoid another one, before colliding still another one ‘as it should’. This can be understood by looking at the relative age of the cracks, the new one avoiding recent ones and being attracted to older ones.

In jellyfish, Aurelia, some new canals grow, similar to cracks. But int this case, the new canal avoids old ones and connect to younger ones. How can we reconcile both phenomena?

Lion’s mane jellyfish, Cyanea, present nice viscous-fingering like patterns. These patterns show the round tip invasion making bifurcating finger into a resisting-squeezed phase, more pointed tips, as can be seen very well in peeling-off experiments. But here, the pattern seems inversed: the invading phase is pointed and the resisting phase is round. How is it possible?

09:25- 09:40

Natalia Kramarz

Many-body dissipative particle dynamics of lipid bilayers with the MDPD-MARTINI force-field

Institute of Physics, Polish Academy of Sciences

Molecular Dynamics (MD) simulations based on the MARTINI coarse-grained model is a well-established approach for studying various systems. However, the MD MARTINI method is computationally expensive, since it is based on Lennard-Jones interactions. Recently [Carnevale and Theodorakis, Eur. Phys. J. Plus 139, 539 (2024)] have demonstrated that the MARTINI force-field approach is suitable for Many-Body Dissipative Dynamics (MDPD), which can offer the same quality of results but at about an order of magnitude of lower computational cost. In this presentation, various lipid bilayers are investigated to demonstrate the potential of the MDPD MARTINI force-field and their various properties are compared with the standard MD MARTINI method.

09:40 - 09:55

Panagiotis Theodorakis

Durotaxis and antidurotaxis motion on gradient substrates

Institute of Physics, Polish Academy of Sciences

The self-sustained motion of droplets on substrates with stiffness gradient is a fascinating phenomenon. Here, we demonstrate designs of brush and gel substrates with stiffness gradient that can cause the droplet motion along (durotaxis) or in the opposite direction of the gradient. Moreover, we elucidate the mechanisms of durotaxis and antidurotaxis motion for each case and we also analyse how it depends on various parameters for the substrate and the droplet. We anticipate that this study provides insights into the self-sustained nanoscale motion of nano-objects onto gradient substrates and guidelines for the experimental design of such substrates.

09:55 - 10:10

Gabriela Niechwiadowicz

Modeling surfactants with the MDPD-MARTINI force-field

Institute of Physics, Polish Academy of Sciences

Surfactants are used in a wide range of industrial applications. This is due to their ability of lowering the surface tension between two phases by preferentially absorbing at their interface, and thus increasing their compatibility. In this presentation, we will discuss details of a many-body dissipative particle dynamics (MDPD) model based on the MDPD-MARTINI force-field [Carnevale and Theodorakis, Eur. Phys. J. Plus, 139, 539 (2024)] for anionic sodium dodecyl sulfate (SDS) surfactant, which is a common industrial surfactant. Our MDPD simulations are carried out for various water–surfactant systems and the relevant properties are analysed and compared with molecular dynamics (MD) simulations based on the MARTINI force-field and experimental data. Details on the computational efficiency of the MDPD and MD models will be provided highlighting the computational speed-up for the MDPD model.

10:10 - 10:25

Luís Carnevale

Lipid Bilayer self assembly simulation with MDPD MARTINI

Institute of Physics, Polish Academy of Sciences

MARTINI is a popular coarse-grained force-field that is mainly used in molecular dynamics (MD) simulations. It is based on the “Lego” approach where intermolecular interactions between coarse-grained beads representing chemical units of different polarity are obtained through water–octanol partition coefficients. This enables the simulation of a wide range of molecules by only using a finite number of parametrized coarse-grained beads, similar to the Lego game, where a finite number of bricks are used to create larger structures. Moreover, the MARTINI force-field is based on the Lennard-Jones potential with the shortest possible cutoff including attractions, thus rendering it very efficient for MD simulations. However, MD simulation is in general a computationally expensive method. Here, we demonstrate that using the MARTINI “Lego” approach is suitable for many-body dissipative particle (MDPD) dynamics, a method that can simulate multi-component and multi-phase soft matter systems in a much faster time (about 4–7 times) than MD. In this study, a DPPC lipid bilayer is chosen to provide evidence for the validity of this approach and various properties are compared to highlight the potential of the method. Thus, we anticipate that our study opens new possibilities for faster simulations of a wide range of soft matter systems by using the MDPD method.

*This research has been supported by the National Science Centre, Poland, under Grant No.2019/34/E/ST3/00232. We gratefully acknowledge Polish high-performance computing infrastructure PLGrid (HPC Centers: ACK Cyfronet AGH) for providing computer facilities and support within computational Grant No. PLG/2022/015747.