Abstracts

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Invited speakers

Laura Rossi (TU Delft) (10:15-11:00)
Effect of shape anisotropy and dipolar interactions on colloidal assembly
Inducing the controlled assembly of colloidal building blocks to prepare the next generation of functional materials with specific mechanical, optical and magnetic properties, requires exceptional control over the interactions between the building blocks. Shape can be a powerful tool to induce and control the assembly of colloidal particles into a variety of structures. However, to engineer novel materials with increased structural complexity, such as low-coordination architectures or metamaterials, it is necessary to induce oriented attachment of the building blocks. In this talk I will show how using inherently directional magnetic dipoles in combination with shape anisotropy can significantly increase the complexity of interaction, giving colloidal particles the freedom to rationally (self-)assemble into precise and adaptable structures.
Melissa Rinaldin (University of Leiden) (11.00-11.30)
Liquid lipid phase separation on curved surfaces
By using colloid supported lipid bilayers of designed shape we proved how the interplay of the shape and the composition of a closed membrane determines the likelihood, the position and the composition of the liquid domains. Here, we show that if we open the membrane by connecting it to a reservoir of lipids, all these three properties are deeply affected. In particular, the pinning of the softer domains in high curvature regions is enhanced, leading to a consistent pattern on all colloids.
Chase Broedersz (LMU Munich) (13.00-13.45)
Broken detailed balance in living systems
How can you tell that a system is out of equilibrium, just by looking at it? To address this question, we employ non-invasive approach to quantify non-equilibrium dynamics in living systems based on broken detailed balance. Using this approach, we study the dynamics of beating flagella, primary cilia, and cytoskeletal networks. In particular, we use stochastic time traces of the system’s dynamics to infer the probability currents in a phase space of the mesoscopic configurational coordinates of a biological assembly. In addition, I will present a more general theoretical framework to investigate what information about the system’s non-equilibrium state can be extracted from such phase space currents. For example, we will discuss how to extract the entropy production rate - a measure of the dissipated power in a driven system – from measured current cycles. Our results provide insight into how internal driving by enzymatic activity generates non-equilibrium dynamics on different scales in soft biological assemblies.
Arjan Boerma (University of Groningen) (13.45-14.15)
Cross-linker dynamics as a mechanism for visco-elasticity
In the cytoskeleton, biopolymers such as actin filaments form networks connected by transient cross-linkers. The diffusion of cross-linker molecules affects the mechanical properties of cytoskeletal networks, which is central to their role in biological functions such as cell motility and force transduction. We examine the origin of visco-elasticity in a minimal model system using coupled finite-element/Monte Carlo simulations, and discuss the implications for the rheology of transiently cross-linked networks.
Shari Finner (TU Eindhoven) (15.30-16.00)
Percolation in Nematic Liquid Crystals of Slender Nanoparticles
In this talk, I will address the topic of continuum percolation in dispersions of hard slender particles that form liquid-crystalline phases. The formation of transient nanoparticle networks in this type of dispersion must clearly depend on the symmetry of the underlying phase. By connecting the percolation transition to spontaneous symmetry breaking, we show that network formation in the uniaxial nematic phase of slender nanoparticles is fundamentally different from that in isotropic dispersions: clusters are strongly elongated, and the cluster size is virtually independent of the particle density! This unexpected result is due to a nontrivial coupling between the density and the degree of orientational order, which both affect the mean surface-to-surface distance of neighbouring particles. Our conclusions hold not only in the limit of perfectly straight and monodisperse nanofillers, but also for those that are polydisperse, and those that are helical and support a chiral nematic phase.
Ben Werkhoven (University of Utrecht) (16.00-16.30)
Dynamic Surface Charges in Electrokinetic Systems
We theoretically study the electrokinetic problem of a pressure-induced liquid flow through a narrow long channel with charged walls, going beyond the classical Helmholtz-Schmolukowski picture by considering the surprisingly strong combined effect of (i) Stern-layer conductance and (ii) dynamic charge-regulating rather than fixed surface charges. We find that the water flow induces, apart from the well-known streaming potential, also a strongly heterogeneous surface charge and zeta potential on chemically homogeneous channel walls. Moreover, we identify a novel steady state with a nontrivial 3D electric flux with 2D surface charges acting as sources and sinks. We furthermore identify three time scales that govern the behaviour of this novel steady state. For a pulsed pressure drop our findings also provide a first-principles explanation for ill-understood experiments on the effect of flow on interfacial chemistry. We will finish with some recent work, and show how surfaces with multiple adsorption/desorption reactions exhibit interesting behaviour, such as an induced charge inversion.

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