Department of Materials Science & Engineering
Massachusetts Institute of Technology
Director, MIT Program in Polymers and Soft Matter
Abstract: Spinning Colloids: Non-Equilibrium Assembly, Transport and Work
Interactions between particles as well as transport processes lie at the core of our understanding of materials. While much work has been devoted to understanding how such interactions control the equilibrium behavior of a myriad of systems, for active systems we are just beginning to piece together how they behave. Here, we will present our work on spinning colloids, which can be through as micro vortices, and describe their effective interactions and their transport mechanisms in different conditions. Spinning colloids have emerged as a new class of active materials with very interesting properties, and have several similarities to quantum systems. In the first part of this talk we will describe how such spinners interact with each other in the presence of different media. In the last few years we have discovered an emergent ultra-long range interaction between such spinning colloids, which is only due to the non-equilibrium conditions experienced in the system. This interaction is tunable and one can change the system from macro-phase separated to micro-phase separated to mixed by simply changing the rotation frequency and direction. In the second part we will present our work on the transport of such colloids in ordered and disordered environments. Contrary to intuition, these spinning colloids display disorder induced delocalization, but upon introducing periodic inversions in the spinning direction one can fully control transport in periodic systems also. An interesting outcome of the transport processes occurring under a drive for such spinning colloids is the rectification of non-equilibrium work done on the colloids and the role of reversibility. We will conclude with an outlook on the scientific and technological implications for these systems.
Alfredo Alexander-Katz is an associate professor in the Department of Materials Science and Engineering at the Massachusetts Institute of Technology. He obtained his B. Sc. in Physics from the Universidad Nacional Autonoma de Mexico and his Ph. D. from the University of California at Santa Barbara also in Physics. Following his Ph. D., Professor Alexander-Katz moved to Munich, Germany, as an NSF International Postdoctoral Fellow, and later to Paris, France, as a CNRS Postdoctoral Fellow. His interest lie in the realm of synthetic and biological soft materials, of which the latter are the building blocks of our bodies going from the molecular nanometer scale all the way up to the cellular and organ scale. In particular, he is interested in driven soft-matter systems that can display a wide range conformations with minimal energy input, offering interesting opportunities for development of active and responsive materials. He has worked on a range of topics that include microscopic propulsion, blood clotting, and block copolymer self-assembly. For his work and mentoring, he has been granted multiple awards that include an NSF CAREER award and a DOE Early Career Award, two times best mentor award from DMSE and the 2019 Frank E. Perkins Award for Excellence in Graduate Advising in the School of Engineering.