We present Langevin dynamics simulations that study the collective behavior of driven particles embedded in a densely packed background consisting of passive particles. Depending on the driving force, the densities of driven and passive particles, and the temperature we observe a dynamical phase separation of the driven particles, which cluster together in tight bands. We explore the mechanisms that drive this cluster formation, and determine the critical conditions for such phase separation. A simple physical picture explains the formation and subsequent growth of a jammed zone developing in front of the driven cluster. The model correctly captures the observed scaling with time. We analyze the implications of this clustering transition for the driven transport in dense particulate flows, which due to a non-monotonic dependence on the applied driving force is not straightforwardly optimized. We provide proof-of-concept for a direct application of the clustering effect, and propose a 'colloidal chromatograph'; a setup that permits the separation of colloids by mass or size.
Monte Carlo computer simulations are used to study the segregation behaviour of two polymers under cylindrical confinement. Using a multiple-histogram method, the conformational free energy, F, of the polymers was measured as a function of the centre-of-mass separation distance, λ. We examined the scaling of the free energy functions with the polymer length, the length and diameter of the confining cylinder, the polymer topology (i.e. linear vs ring polymers), and the packing fraction and size of mobile crowding agents. In the absence of crowders, the observed scaling of F(λ) is similar to tha…
Monte Carlo simulations are used to study the translocation of a polymer into a cavity. Modeling the polymer as a hard-sphere chain with a length up to N=601 monomers, we use a multiple-histogram method to measure the variation of the conformational free energy of the polymer with respect to the number of translocated monomers. The resulting free-energy functions are then used to obtain the confinement free energy for the translocated portion of the polymer. We characterize the confinement free energy for a flexible polymer in cavities with constant cross-sectional area A for various cavity sh…
Motivated by recent experiments probing shape, size and dynamics of bacterial chromosomes in growing cells, we consider a polymer model consisting of a circular backbone to which side-loops are attached, confined to a cylindrical cell. Such a model chromosome spontaneously adopts a helical shape, which is further compacted by molecular crowders to occupy a nucleoid-like subvolume of the cell. With increasing cell length, the longitudinal size of the chromosome increases in a non-linear fashion to finally saturate, its morphology gradually opening up while displaying a changing number of helica…
Understanding the bulk and interfacial properties of super-concentrated electrolytes, such as ionic liquids (ILs), has attracted significant attention lately for their promising applications in supercapacitors and batteries. Recently, McEldrew \textit{et al.} developed a theory for reversible ion associations in bulk ILs, which accounted for the formation of all possible Cayley tree clusters and a percolating ionic network (gel). Here we adopt and develop this approach to understand the associations of ILs in the electrical double layer at electrified interfaces. With increasing charge of the …
Motivated by recent nanofluidics experiments, we use Brownian dynamics and Monte Carlo simulations to study the conformation, organization and dynamics of two polymer chains confined to a single box-like cavity. The polymers are modeled as flexible hard-sphere chains, and the box has a square cross-section of side length $L$ and a height that is small enough to compress the polymers in that dimension. For sufficiently large $L$, the system behaviour approaches that of an isolated polymer in a slit. However, the combined effects of crowding and confinement on the polymer organization, conformat…
Dimensional crossover via confinement in the lattice Lorentz gas
Universität Innsbruck（因斯布鲁克大学）；University of Luxembourg（卢森堡大学）；Sapienza Università di Roma（罗马智慧大学）；École Polytechnique Fédérale de Lausanne (EPFL)（洛桑联邦理工学院）；Sorbonne Université（索邦大学）；CNRS（法国国家科学研究中心）
Self-propelled swimmers such as bacteria agglomerate into clusters as a result of their persistent motion. In 1D, those clusters do not coalesce macroscopically and the stationary cluster size distribution (CSD) takes an exponential form. We develop a minimal lattice model for active particles in narrow channels to study how clustering is affected by the interplay between self-propulsion speed diversity and confinement. A mixture of run-and-tumble particles with a distribution of self-propulsion speeds is simulated in 1D. Particles can swap positions at rates proportional to their relative sel…
Wetting-coupled phase separation as an energetic mechanism for active bacterial adhesion
Advanced Materials Thrust, Function Hub, The Hong Kong University of Science and Technology (Guangzhou)（香港科技大学（广州）功能枢纽先进材料交叉中心）；Institute of Chinese Medical Sciences & State Key Laboratory of Mechanism and Quality of Chinese Medicine, University of Macau（澳门大学中国医药研究国家重点实验室及中医药研究所）；Department of Pharmaceutical Sciences, Faculty of Health Sciences, University of Macau（澳门大学健康科学学院药学系）；Zhuhai UM Science and Technology Research Institute, University of Macau（澳门大学珠海科学技术研究院）；Platform for Structure and Functional Technology of Neural Network, Guangdong Institute of Intelligence Science and Technology（广东省智能科学技术研究院神经网络结构与功能技术平台）
