|9:00||Ray Kapral||Chemically-powered nanomotors: What makes them move, their individual and collective behavior, and why particle-based methods are needed to study their dynamics|
|10:45||Steve Ebbens||Catalytic Micro-swimmers: Progress and Future Challenges|
|13:30||Marisol Ripoll||Thermophoretically powered micromachines|
|14:45||Ayusman Sen||Designing Chemically-Powered Nanomotors and Pumps|
|9:00||Pierre de Buyl & MJ Huang||Setting up software for mesoscopic simulations|
|10:30||Simulation of nanodimer motors|
|14:00||Case studies (flows, motor type)|
Bio: Dr Steve Ebbens conducts active colloids research within the Department of Chemical and Biological Engineering at the University of Sheffield, UK. His particular focus is on developing catalytic swimming devices to enable applications, with an emphasis on the importance of autonomy. Dr Ebbens and his research group are supported by a EPSRC career acceleration fellowship award.
Abstract: This talk will give an overview of catalytic micro-swimmers research within my group, with a strong focus on spherical Janus colloids. Two key themes will be explored, the first concerning efforts to control device trajectories in order to enable applications. Starting from exploring the fundamental Brownian processes that determine swimmer trajectory, a wide range of strategies for control will be surveyed including self-assembly, catalytic patch shape engineering, size changes, gravitaxis and physical guidance. A second theme will highlight the way in which experimental observations have informed the development of models for the propulsion producing mechanism for catalytic micro-swimmers, and the impact that these mechanistic insights have on future applications. Finally, a future perspective for the challenges remaining for micro-swimmers will be offered, contrasting spherical Janus micro-swimmers with bubble releasing micro-rockets.
Bio: Ray Kapral is professor in the Chemical Physics Theory Group at the University of Toronto. He has published about 290 articles and pioneered the widely used Multiparticle Collision Dyanmics simulation algorithm. His 2007 work on chemically powered nanodimers started a successful line of research that has since been extended to Angström-scale motors, enzyme machines or the study of collective dynamics.
Abstract: The title says it all. The talk will consider the phoretic mechanisms that operate to propel synthetic nanomotors in solution. Like their biological counterparts, these motors operate in low Reynolds number conditions where inertia is not important. Their individual motions, as well as the collective dynamics of many motors, are controlled by hydrodynamic flow fields and chemical gradients generated by asymmetric catalytic reactions on the motors. In order to describe the complex hydrodynamic flow fields and chemical gradient effects, which require the solution of a difficult many-body problem for systems with many motors, molecular simulation schemes that automatically and accurately account for these effects need to be employed. Since the motors are small, some even with linear dimensions of even a few nanometers, fluctuations and solvent structural effects are important and continuum descriptions may break down. In such regimes molecular descriptions are essential and methods to deal with these issues will be discussed. Synthetic nanomotors have the potential for use in a wide range of new applications and present challenges for fundamental theory. These factors have stimulated the considerable research activity that is being undertaken in this area.
Bio: Marisol Ripoll studied Theoretical Physics in UCM (Spain) and did her PhD in between UNED (Spain) and Utrecht University (The Netherlands). She went to Forschungszentrum Jülich (Germany) for a postdoctoral stay and got there the chance to lead a Young Investigators Group and to become a scientific researcher. In her research she typically uses mesoscopic simulations to understand the properties and behavior of soft matter systems like colloids, polymers or liquid crystals. Of special interest are hydrodynamic interactions, shear induced effects, microfluidics, thermophoresis, active matter, and synthetic micromachines.
Abstract: Thermophoresis refers to the drift experienced by particles subject to a temperature inhomogeneity. A relatively new strategy in the design of synthetic micromotors is based in structures with asymmetric composition or shape subject to a self-sustained temperature gradient. In this talk, I will show how the concepts introduced by Ray Kapral about the simulation of hydrodynamic interactions and flows can be nicely applied and adapted to include the thermophoretic behavior. Starting with the simulation of colloidal thermophoresis, the implementation of self-propelled structures like Janus single colloids and dimers can extended to propose other phoretic powered structures, like rotating gears, turbines, rheometers, and various types of pumps. Devices based on this principle can then be very versatile to manipulate complex fluids and a promising tool to recover waste heat, or to facilitate cooling of microchips.
Bio: Ayusman Sen received his Ph.D. from the University of Chicago and was a postdoctoral fellow at the California Institute of Technology. He is a Distinguished Professor of Chemistry at the Pennsylvania State University. He is a Fellow of the American Association for the Advancement of Science and the Royal Society of Chemistry. His research interests encompass catalysis, polymer science, and nanotechnology. He is the author of approximately 350 scientific publications with an H-index of 68, and holds 24 patents.
Abstract: Self-powered nano and microscale moving systems are currently the subject of intense interest due in part to their potential applications in nanomachinery, nanoscale assembly, robotics, fluidics, and chemical/biochemical sensing. We will demonstrate that one can build autonomous nanomotors over a wide range of length-scales “from scratch” that mimic biological motors by using catalytic reactions to create forces based on chemical gradients. These motors are autonomous in that they do not require external electric, magnetic, or optical fields as energy sources. Instead, the input energy is supplied locally and chemically. These "bots" can be directed by information in the form of chemical and light gradients. Furthermore, we have developed systems in which chemical secretions from the translating nano/micromotors initiate long-range, collective interactions among themselves. This behavior is reminiscent of quorum sensing organisms that swarm in response to a minimum threshold concentration of a signaling chemical. In addition, an object that moves by generating a continuous surface force in a fluid can, in principle, be used to pump the fluid by the same catalytic mechanism. Thus, by immobilizing the nano/micromotors, we have developed nano/microfluidic pumps that transduce energy catalytically. These non-mechanical pumps provide precise control over flow rate without the aid of an external power source and are capable of turning on in response to specific analytes in solution.
On the second day of the workshop, a hands-on simulation session will take place, using the code RMPCDMD. Instructions on the installation and execution of the program will be given and the program's internal structure will be exposed. The aims of this session are twofold: (i) Enable the use of a working nanomotor simulation code by participants and (ii) expose the simulation methodology to enable participants to use it as a base for further research and/or developments. The dimer nanomotor of Rückner and Kapral will be presented in the morning. Suggestions from the participants are welcome for the afternoon. Possible topics include thermal reactions, flows or Janus geometry.
Bio: Pierre de Buyl is a postdoctoral fellow at the Institute for Theoretical Physics of the KU Leuven where he focuses on the theoretical modeling of active particles systems. He is developing an open simulation code RMPCDMD with the objective of understanding fundamental issues in the self-propelled motion of nanomotors as well as experimenting with relevant experimental situations (flows, etc).
Bio: Mu-Jie Huang holds a PhD from the National Central University of Taiwan where he worked on mesoscopic simulations of active machines in lipid bilayers. Since 2014 he is a postdoctoral fellow with Ray Kapral in Toronto where he extends his studies to other molecular machines and to synthetic nanomotors.