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Active Matter

1. Collective Responses of the Microswimmers

Magnetic microswimmers have been attracting attentions recently due to their potential use in applications such as drug/cargo delivery in bio-systems. In physics, these microswimmers can have fascinating dynamic responses when subjected to an external magnetic field, such as focusing and clustering of magnetotactic bacteria in a microfluidic channel. We are currently developing both analytic models and numerical simulations to understand their collective behaviours in different circumstances.

  • F. Meng, D. Matsunaga, B. Mahault and R. Golestanian*, "Magnetic Microswimmers Exhibit Bose-Einstein-Like Condensation." Physical Review Letters 126, 078001 (2021). 
  • F. Meng, D. Matsunaga, and R. Golestanian*, "Clustering of magnetic swimmers in a Poiseuille flow." Physical Review Letters 120, 188101 (2018). 

2. Emergent Dynamics of the Colloids, and Rotors

Magnetic colloids can interact with each other via many-body interactions including magnetic dipole-dipole interaction and hydrodynamic interaction. Controlled by external magnetic field, the out-of-equilibrium magnetic colloids and rotors can form complex structures and show interesting emergent dynamics. By comparing the theoretical results and the experimental outcomes, we try to understand how to control the collective responses of magnetic colloids, etc. 

  • F. Meng#,  Antonio Ortiz-Ambriz#, Helena Massana-Cid, Andrej Vilfan, R. Golestanian, and P. Tierno*, "Field synchronized bidirectional current in confined driven colloids." Physical Review Research 2, 012025(R) (2020). 
  • T. Kawai,  D. Matsunaga*, F. Meng*, J. Yeomans, and R. Golestanian, "Degenerate states, emergent dynamics and fluid mixing by magnetic rotors." Soft Matter 16, 6484-6492 (Featured as back cover article) (2020).
  • H. Massana-Cid#F. Meng#, D. Matsunaga, R. Golestanian*, and P. Tierno*, "Tunable self-healing of magnetically propelling colloidal carpets." Nature Communications 10, 2444 (2019). 
  • D. Matsunaga#, J. Hamilton#F. Meng, N. Bukin, E. L. Martin, F. Ogrin, J. Yeomans and R. Golestanian*, "Tunable self-healing of magnetically propelling colloidal carpets." Nature Communications 10, 4696 (2019). 

3. Cilia Synchronisation

Cilia interact with each other via hydrodynamic coupling, and then move collectively in the form of a metachronal wave. By constructing an analytic theory and performing agent-based simulations, we reveil the conditions for achieving the wave patterns. 

  • F. Meng#, R. Bennett#, N. Uchida, and R. Golestanian*, "Conditions for metachronal coordination in arrays of model cilia",  Proceedings of the National Academy of Sciences USA, in press (Arxiv) (2021).

4. Individual Magnetic Cilium and Ellipsoid

The interplay of magnetic control and hydrodynamic interaction with the confinement can induce useful dynamics of individual magnetic unit such as magnetic cilium and magnetic ellipsoid, which can be applied for fluid transport and as solution stirrer and particle sorter. By developing analytic theories for such systems, we can propose how to fabricate magnetic units with desired dynamic properties and their controls from the physical perspective. 

  • F. Meng, D. Matsunaga, J. Yeomans, and R. Golestanian*, "Magnetically-Actuated Articial Cilium: A Simple Theoretical Model." Soft Matter 15, 3864-3871 (Featured as inside back cover article) (2019). 
  • D. Matsunaga*, A. Zoettl, F. Meng, R. Golestanian, and J. M. Yeomans, "Far-field theory for trajectories of magnetic ellipsoids in rectangular and circular channels." IMA Journal of Applied Mathematics 83, 767–782 (2018). 
  • D. Matsunaga, F. Meng, A. Zoettl, R. Golestanian, and J. M. Yeomans*, "Focusing and sorting of ellipsoidal magnetic particles in microchannels." Physical Review Letters 119, 019802 (Editors' suggestion; Highlighted in APS Physics Synopsis) (2017). 

5. Active Nematics... (to appear)