Special Issue "Dynamics of Active Matter"

A special issue of Condensed Matter (ISSN 2410-3896).

Deadline for manuscript submissions: 15 December 2019.

Special Issue Editor

Prof. William E. Uspal
E-Mail Website
Guest Editor
Department of Mechanical Engineering, University of Hawai'i at Manoa, POST 207, USA
Interests: microhydrodynamics; statistical mechanics; active matter; self-organization; soft matter simulation

Special Issue Information

The past decade has witnessed an explosion of interest in active matter, i.e., materials systems whose constituent particles consume energy and generate mechanical motion or work. Paradigmatic examples of active particles include catalytically active Janus colloids, which consume molecular “fuel” in order to swim through solution; flagellated and ciliated biological microswimmers, such as e. coli and opalina; and the nanoscale machinery of the cell, such as the kinesin motor protein. The intrinisically nonequilibrium character of active systems can lead to novel emergent structures and dynamics. For instance, individual active particles can bind to, and move along, confining solid surfaces through hydrodynamic interactions; two or more active colloids can self-organize into “active molecules” through non-reciprocal interactions; and collections of many particles can form dynamic “living clusters” or exhibit mesoscale turbulence.

This initial decade of work established some basic conceptual frameworks for understanding active matter. For instance, the hydrodynamic or continuum approach to colloidal phoresis has been successfully adapted to modeling the motion of catalytically active Janus colloids in unbounded and confined solutions. Motility-induced phase separation has been systematically characterized in simulations of active Brownian particles. Additionally, hydrodynamic and kinetic theories that treat an active suspension as a fluid have captured aspects of swarming, flocking, and mesoscale turbulence. Current research is seeking, inter alia, to extend these core approaches and results to more complex and multiphysical scenarios. Accordingly, potential topics for this Special Issue include:

  • Tactic response of active particles to ambient fields (e.g., chemical, hydrodynamic, optical, and acoustic fields). Recent work has explored how the microscopic properties of a Janus colloid (e.g., shape and surface chemistry) are related to macroscopic transport coefficients (e.g., drift velocity and diffusivity) in ambient fields. Similarly, the relationhip between the microscopic run-and-tumble dynamics of micro-organisms and population-level chemotactic and rheotactic behavior has acquired new importance in light of recent particle tracking experiments.
  • Rheology of active fluids. Experiments and theoretical modeling have revealed novel rheological phenomena in suspensions of active particles, including superfluidity and spontaneous macroscopic flow. Potential directions for further research include collective phenomena (i.e., going beyond the dilute limit) and the incorporation of more complex interactions into microscopic dynamics (i.e., going beyond point-particle and squirmer models.)
  • Pattern formation, phase separation, and turbulence arising from the interplay of motility and activity-induced interactions (e.g., chemical signaling and hydrodynamic interactions). The general significance of hydrodynamic interactions for phase separation is still a hotly debated question.
  • Self-organization of dissipative materials and active machines.
  • Swimming in complex media, including porous media and viscoelastic and anisotropic fluids.
  • Statistical mechanics of active matter, including entropy production, fluctuation theorems, and violations of detailed balance.

Prof. William E. Uspal
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All papers will be peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Condensed Matter is an international peer-reviewed open access quarterly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1000 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • active matter
  • active colloids
  • microswimmers
  • self-organization
  • rheology
  • statistical mechanics
  • collective phenomena
  • random walks and diffusion

Published Papers (2 papers)

Order results
Result details
Select all
Export citation of selected articles as:

Research

Jump to: Review

Open AccessArticle
Glucose Oxidase Micropumps: Multi-Faceted Effects of Chemical Activity on Tracer Particles Near the Solid–Liquid Interface
Condens. Matter 2019, 4(3), 73; https://doi.org/10.3390/condmat4030073 - 25 Jul 2019
Abstract
We report the development of glucose oxidase pumps characterized by small lateral dimensions (≈200 μ m). We studied the effects of the activity of the enzyme pump on silica particles (“tracers”) sedimented around the enzyme pump/patch. Once the activity of the pump was [...] Read more.
We report the development of glucose oxidase pumps characterized by small lateral dimensions (≈200 μ m). We studied the effects of the activity of the enzyme pump on silica particles (“tracers”) sedimented around the enzyme pump/patch. Once the activity of the pump was turned on (i.e., the glucose substrate was added to the solution), in-plane motion of the tracers away from the enzyme patch, as well as the emergence of an in-plane region around the patch which was depleted by tracers, was observed. The lateral extent of this depletion zone increased in time at a rate dependent both on the glucose concentration and on the areal density of the enzyme in the patch. We argue that, when the tracers were very near the wall, their motion and the emergence of the depletion zone were most likely the result of diffusiophoresis and drag by osmotic flows induced at the wall, rather than that of drag by a solutal buoyancy driven convective flow. We infer that, for the glucose oxidase enzymatic pumps, bulk (solutal buoyancy), as previously reported, as well as surface (osmotic) driven flows coexist and have to be explicitly accounted for. It seems plausible to assume that this is the case in general for enzyme pumps, and these complementary effects should be considered in the design of applications, e.g., stirring or sensing inside microfluidic systems, based on such pumps. Full article
(This article belongs to the Special Issue Dynamics of Active Matter)
Show Figures

Figure 1

Review

Jump to: Research

Open AccessReview
Review: Interactions of Active Colloids with Passive Tracers
Condens. Matter 2019, 4(3), 78; https://doi.org/10.3390/condmat4030078 - 23 Aug 2019
Abstract
Collective phenomena existing universally in both biological systems and artificial active matter are increasingly attracting interest. The interactions can be grouped into active-active and active-passive ones, where the reports on the purely active system are still clearly dominating. Despite the growing interest, summarizing [...] Read more.
Collective phenomena existing universally in both biological systems and artificial active matter are increasingly attracting interest. The interactions can be grouped into active-active and active-passive ones, where the reports on the purely active system are still clearly dominating. Despite the growing interest, summarizing works for active-passive interactions in artificial active matter are still missing. For that reason, we start this review with a general introduction, followed by a short spotlight on theoretical works and then an extensive overview of experimental realizations. We classify the cases according to the active colloids’ mechanisms of motion and discuss the principles of the interactions. A few key applications of the active-passive interaction of current interest are also highlighted (such as cargo transport, flow field mapping, assembly of structures). We expect that this review will help the fundamental understanding and inspire further studies on active matter. Full article
(This article belongs to the Special Issue Dynamics of Active Matter)
Show Figures

Figure 1

Back to TopTop