Article
Chemistry, Multidisciplinary
Richard J. Archer, Stephen J. Ebbens
Summary: This study investigates the motile behavior of symmetrical catalytic colloids produced by a solution-based metal salt reduction process. It finds that despite differences in catalytic activity distribution, the motion produced by symmetrical colloids is equivalent to that of Janus colloids. The findings suggest that subtle variations in surface reactivity can produce Janus-like active Brownian particle motion.
Article
Multidisciplinary Sciences
Jaideep Katuri, Ruben Poehnl, Andrey Sokolov, William Uspal, Alexey Snezhko
Summary: This study reveals unconventional motion states in ensembles of active discoidal particles powered by induced-charge electrophoresis. Through experiments and computational modeling, researchers demonstrate that the shape asymmetry of the particles promotes the formation of active particles' bound states, ultimately leading to a spontaneous collective state with arrested motility.
Article
Chemistry, Multidisciplinary
Lijie Lei, Rong Cheng, Yuxiu Zhou, Tiezhu Yang, Beirong Liang, Shuo Wang, Xinyuan Zhang, Guanhua Lin, Xuemao Zhou
Summary: This paper investigates the effect of anisotropy on the self-propulsion velocity of active colloids and finds that both size and concentration field play important roles in the self-propulsion mechanism, providing a new way to control the dynamics of active colloids.
FRONTIERS IN CHEMISTRY
(2022)
Article
Mechanics
Nicholas G. Chisholm, Kathleen J. Stebe
Summary: The study investigates the far-field flows generated by externally driven and active colloids at planar fluid-fluid interfaces, considering different scenarios and the impact of interfacial incompressibility. The behavior of driven and active colloids in these conditions differs significantly, restructuring the leading-order modes for each type of colloid and introducing new flow patterns.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Chemistry, Multidisciplinary
Priyanka Sharan, Witold Postek, Thomas Gemming, Piotr Garstecki, Juliane Simmchen
Summary: This study systematically investigated the motion of Pt@SiO2 Janus particles at a liquid-liquid interface, finding that the propulsion behavior on both oil-water and solid-water interfaces is quantitatively similar. The motion characteristics are controlled by factors such as reaction product absorption by oil, slip locking by surfactant, and potential Marangoni effect.
Article
Chemistry, Multidisciplinary
Lukasz Baran, Malgorzata Borowko, Wojciech Rzysko, Jakub Smolka
Summary: We use Monte Carlo simulations to investigate the behavior of Janus spheres composed of attractive and repulsive parts confined between two parallel solid surfaces. The adsorption isotherms and the impact of density on morphology are determined. Unique structures such as bilayer and three-layer structures at different distances from the walls are observed. The positional and orientational ordering in these layers are affected by selected parameters, with highly ordered hexagonal lattices formed in some cases.
Article
Chemistry, Physical
Denise Chirinos-Flores, Rodrigo Sanchez, Pedro Diaz-Leyva, Anna Kozina
Summary: The study investigates the structure and dynamics of asymmetrically decorated silica-based Janus particles in a hydrophobic solvent, observing gelation of amphiphilic Janus particles with asymmetric surface decoration in the hydrophobic medium. The influence of particle asymmetry on gel structure and dynamics is discussed, revealing compact structures with contributions of asymmetric short-range attractions and cross-term repulsions to the net effective interaction potential.
JOURNAL OF COLLOID AND INTERFACE SCIENCE
(2021)
Article
Chemistry, Physical
Dinesh Kumar Sahu, Surajit Dhara
Summary: We studied the electrophoresis behavior of metal-dielectric Janus particles with dipolar director symmetry in two nematic liquid crystals and found that the Janus dipolar particles exhibit higher propelling speed and electrophoretic efficiency compared to other Janus particles.
Article
Chemistry, Multidisciplinary
Jiao Zhu, Huaguang Wang, Zexin Zhang
Summary: The study demonstrates a facile strategy to synthesize Janus micromotors with precisely tunable shapes, providing an important foundation for the creation of intelligent and functional micromachines.
Article
Chemistry, Multidisciplinary
Priyanka Sharan, Zuyao Xiao, Viviana Mancuso, William E. Uspal, Juliane Simmchen
Summary: Fluid flow is common in microorganism habitats, and both biological and artificial microswimmers respond to flows influenced by chemical and physical factors. This study introduces Cu@SiO2 micromotors and investigates their behavior under externally applied flows. The micromotors exhibit puller-type characteristics and display jumping behavior at high flow speeds.
Article
Mechanics
R. Fantoni, M. A. G. Maestre, A. Santos
Summary: This study revisits the equilibrium properties of a Janus fluid made of two-face particles confined to a one-dimensional channel, deriving the exact Gibbs free energy for a finite number of particles N and proving that the results for both classes of systems tend to a common expression in the thermodynamic limit. The theoretical finite-size results are confirmed by Monte Carlo simulations for the Kern-Frenkel model in both quenched and annealed systems.
JOURNAL OF STATISTICAL MECHANICS-THEORY AND EXPERIMENT
(2021)
Article
Physics, Fluids & Plasmas
Pavol Kalinay, Frantisek Slanina
Summary: We studied a self-driven Janus particle with a constant driving force, which can change its direction randomly due to the stochastic rotation. The particle diffuses in a two-dimensional channel with varying width. By mapping the 2 + 1-dimensional Fokker-Planck equation onto the longitudinal coordinate, we obtained the Fick-Jacobs equation with spatially dependent diffusion constant and an additional effective potential.
Article
Chemistry, Physical
A. M. Boymelgreen, G. Kunti, P. Garcia-Sanchez, A. Ramos, G. Yossifon, T. Miloh
Summary: The study investigates the interaction between active particles and walls to explain discrepancies between experiments and theory. The findings show that the motion direction and frequency dispersion of particles can be controlled by the interaction between ICEP and sDEP. Proximity to walls enhances this interaction and has a significant impact on particle mobility.
JOURNAL OF COLLOID AND INTERFACE SCIENCE
(2022)
Article
Chemistry, Multidisciplinary
Jong Bin Kim, Ji-Won Kim, Minjung Kim, Shin-Hyun Kim
Summary: This study presents a simple strategy to produce electro-responsive Janus microspheres with both photonic and plasmonic faces for active color change. The orientation control of the Janus microspheres with an external electric field enables the switchability of the photonic and plasmonic colors.
Article
Chemistry, Multidisciplinary
Jin Gyun Lee, Cooper P. Thome, Zoe A. Cruse, Arkava Ganguly, Ankur Gupta, C. Wyatt Shields
Summary: This study presents a method of magnetically assembling locked clusters of Janus particles, which display diverse trajectories when stimulated by AC electric fields. The orientation of particles within each cluster determines the different modes of locomotion. The predicted and experimentally observed cluster trajectories show qualitative agreement. This method provides a scalable way to create micromotors with a range of well-defined motions.
Article
Chemistry, Physical
Raluca-Elena Munteanu, Mihail N. Popescu, Szilveszter Gaspar
Summary: The study investigates the influence of confinement on the response of silica tracer particles near a chemically active glucose oxidase patch immersed in a glucose solution. A region depleted of tracers forms around the patch regardless of the height H within the explored range. The rate of growth of the depletion zone depends on H when H is not much larger than the patch radius, and this dependence is influenced by the glucose concentration.
COLLOID AND POLYMER SCIENCE
(2021)
Article
Multidisciplinary Sciences
Rumen N. Georgiev, Sara O. Toscano, William E. Uspal, Bram Bet, Sela Samin, Rene van Roij, Huseyin Burak Eral
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
(2020)
Review
Chemistry, Multidisciplinary
Yi Y. Zuo, William E. Uspal, Tao Wei
Article
Chemistry, Physical
Martin Wittmann, Mihail N. Popescu, Alvaro Dominguez, Juliane Simmchen
Summary: The experiment with spherically symmetric active TiO2 particles at an oil-water interface confirmed that collective dynamics can arise from activity-induced gradients, leading to long-ranged Marangoni flows even when particles are not self-propelled. The addition of a nonionic surfactant was shown to influence the emergence of collective motion, with dynamics dependent on particle coverage in the monolayer. The experimental observations were discussed within a simple theoretical mean-field model.
EUROPEAN PHYSICAL JOURNAL E
(2021)
Article
Multidisciplinary Sciences
Jaideep Katuri, William E. Uspal, Mihail N. Popescu, Samuel Sanchez
Summary: Experimental studies reveal complex effective interactions between sedimented silica particles on a wall and active Pt/silica Janus particles. Indirect methods are needed to analyze the fields induced by activity.
Article
Mechanics
Ruben Poehnl, William Uspal
Summary: The study investigates the motion of chemically active colloids in the form of rotating helices, revealing that the translational and rotational velocities of the particles depend on geometry and the distribution of catalytic activity on the surface. Both tangential and circumferential concentration gradients contribute to the particle velocity, with their relative importance impacting the motion of the particle. By selecting specific particle design parameters, it is possible to control and even suppress certain components of angular velocity, affecting the translation of the helix.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Chemistry, Multidisciplinary
Priyanka Sharan, Zuyao Xiao, Viviana Mancuso, William E. Uspal, Juliane Simmchen
Summary: Fluid flow is common in microorganism habitats, and both biological and artificial microswimmers respond to flows influenced by chemical and physical factors. This study introduces Cu@SiO2 micromotors and investigates their behavior under externally applied flows. The micromotors exhibit puller-type characteristics and display jumping behavior at high flow speeds.
Review
Chemistry, Physical
Alvaro Dominguez, Mihail N. Popescu
Summary: Phoresis, a classic example of particle transport driven by thermodynamic gradients, is enjoying renewed research interest due to its relevance to the motility of chemically active particles and technological advancements. This review focuses on the general framework of phoresis and self-phoresis, using chemophoresis as a case study, and discusses the simplest extension of the theory to account for correlations in the fluid. It is found that self-phoresis can no longer be represented as phoresis in a self-generated composition gradient, shifting the paradigm from the ideal case.
CURRENT OPINION IN COLLOID & INTERFACE SCIENCE
(2022)
Article
Multidisciplinary Sciences
Jaideep Katuri, Ruben Poehnl, Andrey Sokolov, William Uspal, Alexey Snezhko
Summary: This study reveals unconventional motion states in ensembles of active discoidal particles powered by induced-charge electrophoresis. Through experiments and computational modeling, researchers demonstrate that the shape asymmetry of the particles promotes the formation of active particles' bound states, ultimately leading to a spontaneous collective state with arrested motility.
Review
Chemistry, Analytical
Mihail N. Popescu, Szilveszter Gaspar
Summary: Catalytic micromotors can be used to detect molecules of interest either by analyzing their motion or by enhancing mass transport. Analyzing the motion of the micromotors provides an analytical signal that can be used for sensing fuel or modulating species. Alternatively, the micromotors can enhance specific recognition events in a sample without analyzing their motion. Qualitative analysis of small samples in resource poor environments is the most promising application for catalytic micromotors in analytical chemistry.
Article
Chemistry, Multidisciplinary
Marek Bekir, Marcel Sperling, Daniela Vasquez Munoz, Cevin Braksch, Alexander Boeker, Nino Lomadze, Mihail N. Popescu, Svetlana Santer
Summary: Separation of particles by size, morphology, or material identity is important in filtration or bioanalytics. However, the separation of particles solely based on surface properties or bulk/surface morphology remains challenging. This study proposes a combination of pressure-driven microfluidic flow and local self-phoresis/osmosis induced by a photoactive azobenzene-surfactant solution. The separated colloidal components experience different regions of the ambient microfluidic shear flow, allowing for a simple, versatile method of particle chromatography.
ADVANCED MATERIALS
(2023)
Article
Chemistry, Physical
P. D. Neta, M. Tasinkevych, M. M. Telo da Gama, C. S. Dias
Summary: A lattice model was used to study repulsive active particles on a planar surface, with a rejection-free Kinetic Monte Carlo method employed. The model predicted a motility-induced phase separation and the coexistence of dense liquid-like and dilute vapour-like steady states. By introducing an ensemble analogous to a grand canonical ensemble, the formation and growth of a liquid film between solid surface and vapour phase were investigated.
Article
Chemistry, Physical
Tomasz Skora, Mihail N. Popescu, Svyatoslav Kondrat
Summary: Studies show that crowding can increase the diffusion of enzymes when only enzymes are present, but decrease it when inert particles are present. Additionally, the diffusion enhancement of tracers is influenced by increasing enzyme concentration.
PHYSICAL CHEMISTRY CHEMICAL PHYSICS
(2021)
Article
Chemistry, Multidisciplinary
Blaise Fleury, Bohdan Senyuk, Mykola Tasinkevych, Ivan I. Smalyukh