Pietro Tierno
Associate professor
Department of Condensed Matter Physics
University of Barcelona
Title: Emergent colloidal currents generated via exchange dynamics in a broken dimer state
Authors:
Antonio Ortiz-Ambriz 1;2, Helena Massana-Cid1;3, Mattia Ostinato 1;2, P. Tierno 1;2;3
1 Departament de Física de la Matèria Condensada, Universitat de Barcelona, 08028 Barcelona, Spain: Email: ptierno@ub.edu
2 Universitat de Barcelona Institute of Complex Systems (UBICS), Universitat de Barcelona, 08028 Barcelona, Spain 3 Institut de Nanociència i Nanotecnologia, Universitat de Barcelona, 08028 Barcelona, Spain
1 Departament de Física de la Matèria Condensada, Universitat de Barcelona, 08028 Barcelona, Spain: Email: ptierno@ub.edu
2 Universitat de Barcelona Institute of Complex Systems (UBICS), Universitat de Barcelona, 08028 Barcelona, Spain 3 Institut de Nanociència i Nanotecnologia, Universitat de Barcelona, 08028 Barcelona, Spain
Abstract: In this talk, I will describe a general strategy to assemble and transport polarizable magnetic microspheres in fluid media through a combination of confinement [1] and magnetic dipolar interactions [2]. We use a homogeneous magnetic modulation to assemble dispersed particles into rotating dimeric state and frustrated binary lattices and generate collective edge currents that arise from a novel, field-synchronized particle exchange process [3]. The observed, net bidirectional current is composed of colloidal particles which periodically meet assembling into rotating dimers, and exchange their positions in a characteristic, “ceilidh”-like dance. We develop a theoretical model that explains the physics of the observed phenomena as dimer rupture and the onset of current, showing agreement with Brownian dynamic simulations [4]. Further, we explore recently the transport of defects as non-magnetic inclusions in ferrofluids media and the anomalous dynamics of the broken/recombining dimers during the exchange process.
Overall, we demonstrate an effective technique to drive microscale matter by using the interplay of steric confinement and dipolar forces, not based on any gradient of the applied field.<br>
References
[1] N. Osterman, I. Poberaj, J. Dobnikar, D. Frenkel, P. Ziherl, and D. Babic Field-Induced Self-Assembly
of Suspended Colloidal Membranes, Phys. Rev. Lett. 103:228301 (2009).
[2] P. Tierno, R: Muruganathan and T. M. Fischer, Viscoelasticity of Dynamically Self-Assembled Paramagnetic
Colloidal Clusters, Phys. Rev. Lett. 98:028301 (2007).
[3] H. Massana-Cid, A. Ortiz-Ambriz, A. Vilfan and P. Tierno, Emergent collective colloidal currents
generated via exchange dynamics in a broken dimer state, Science advances 6:eaaz2257 (2020).
[4] F. Meng, A. Ortiz-Ambriz, H. Massana-Cid, A. Vilfan, R. Golestanian and P. Tierno, Field synchronized
bidirectional current in confined driven colloids, Physical Review Research 2: 012025 (2020).
[1] N. Osterman, I. Poberaj, J. Dobnikar, D. Frenkel, P. Ziherl, and D. Babic Field-Induced Self-Assembly
of Suspended Colloidal Membranes, Phys. Rev. Lett. 103:228301 (2009).
[2] P. Tierno, R: Muruganathan and T. M. Fischer, Viscoelasticity of Dynamically Self-Assembled Paramagnetic
Colloidal Clusters, Phys. Rev. Lett. 98:028301 (2007).
[3] H. Massana-Cid, A. Ortiz-Ambriz, A. Vilfan and P. Tierno, Emergent collective colloidal currents
generated via exchange dynamics in a broken dimer state, Science advances 6:eaaz2257 (2020).
[4] F. Meng, A. Ortiz-Ambriz, H. Massana-Cid, A. Vilfan, R. Golestanian and P. Tierno, Field synchronized
bidirectional current in confined driven colloids, Physical Review Research 2: 012025 (2020).