Soft Matter Soft Matter

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Soft Matter

1. Bio-Polymer Network Theory
Semiflexible filament networks are common in bio-systems, existing as cytoskeleton, extracellular matrix, connective tissues, etc. These filament networks exhibit unique mechanic properties compared with flexible polymer networks such as rubbers. We try to develop continuum theories to understand the complex viscoelastic properties of both permanently and transiently crosslinked filament networks. 
  • F. Meng, and E. Terentjev*, "Nonlinear elasticity of semiflexible filament networks." Soft Matter 12, 6749-6756 (2016)
  • F. Meng, and E. Terentjev*, "Theory of semiflexible filaments and networks." Polymers 9, 52 (2017)
  • F. Meng, and E. Terentjev*, "Fluidisation of transient filament networks." Macromolecules 51, 4660–4669 (2018)
2. Transiet Polymer Network Modelling
In self-healing materials, the crosslinks networking the polymers can dynamically break and re-form, i.e., transient bonds. Due to the dynamic features of the crosslinks, the transient network can exhibit interesting viscoelastic responses, and we are developing continuum theories to understand its rheological properties.
  • F. Meng, R. H. Pritchard, and E. Terentjev*, "Stress relaxation, dynamics and plasticity of transient polymer networks." Macromolecules 49,2843-2852 (2016)
  • F. Meng, and E. Terentjev*, "Transient network at large deformations: elastic-plastic transition and necking instability." Polymers 8, 108 (2016)
  • J.-H. Chen, D.-D. Hu, Y.-D. Li, F. Meng*, J. Zhu, and J.-B. Zeng*, "Castor oil derived poly (urethane urea) networks with reprocessibility and enhanced mechanical properties." Polymer 143, 79-86 (2018)
  • F. Meng*, M. Saed and E. Terentjev*, "Elasticity and relaxation in full and partial vitrimer networks." Macromolecules527423-7429 (2019)
3. Drying Soft Matter Solutions
When soft matter solutions are being dried, there can be several sub-processes including solvent evaporation, solute diffusion, gel layer formation, etc. After drying process finishes, solutions can result in various forms such as coffee rings, solid particles, hollow particles, etc. We try to understand how different morphologies of soft matter solutions can evolve by constructing theoretical dynamic theories. 
  • F. Meng, M. Doi*, and Z-C. Ouyang, "Cavitation in drying droplets of soft matter solutions."Physical Review Letters 113, 098301 (2014)
  • F. Meng*, L. Luo, M. Doi* and Z-C. Ouyang, "Solute based Lagrangian scheme in modeling the drying process of soft matter solutions."European Physical Journal E 39, 22 (2016)
  • L. Luo, F. Meng, J. Zhang, and M. Doi*, "Skin formation in drying a film of soft matter solutions -- application of solute based Lagrangian scheme." Chinese Physics B 25, 076801 (2016)
4. Rubber/Gel Elasticity
Rubbers/gels are ubiquitous in our daily life, and in physics they are interesting in terms of their tunable mechanic properties. By utilizing the elastic theories, we can understand how and why rubber systems can behave under specific circumstances (for example, how to inflate a balloon in your childhood). 
  • F. Meng, J. Z. Y. Chen, M. Doi*, and Z-C. Ouyang, "Phase diagrams and interface in inflating balloon." AIChE Journal 60, 1393–1399 (2014)
  • F. Meng, J. Z. Y. Chen, M. Doi*, and Z-C. Ouyang, "Critical line in twisting instabilities of soft tubes." Soft Matter 11, 7046-7052 (2015)
  • F. Meng, M. Doi, Z-C. Ouyang, X. Zheng, and P. Palffy-Muhoray*, "The 'coin-through-the rubber' trick: an elastically stabilized invagination." Journal of Elasticity 123, 43–57 (2015)
  • S. Varol, F. Meng, B. Hosseinkhani, C. Malm, D. Bonn, M. Bonn, A. Zaccone, and S. H. Parekh*, "Nanoparticle amount, and not size, determines chain alignment and nonlinear hardening in polymer nanocomposites." Proceedings of the National Academy of Sciences USA 114, E3170–E3177 (2017)
5. Liquid-Liquid Phase Transition
Liquid-liquid phase transition is treated as connected to the formation of membraneless organelles in cells, and we try to construct a continuum theory for understanding the criterion of such transition and predicting the phase separated products in a liquid mixture constrained by an elastic network. 

Active Matter Active Matter

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Active Matter

1. Collective Responses of Magnetic 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, and R. Golestanian*, "Clustering of magnetic swimmers in a Poiseuille flow." Physical Review Letters 120, 188101 (2018)
  • F. Meng, D. Matsunaga, B. Mahault and R. Golestanian*, "BEC of magnetic swimmers in a circular channel." to appear

2. Emergent Dynamics of Magnetic 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. 

  • 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). (#: Co-first authors)
  • 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). (#: Co-first authors)
  • 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). (#: Co-first authors)
  • 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).

3. 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. 

  • 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)
  • 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)
  • 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). 

4. Active Nematics... (to appear)