Janus Particles & Soft Matter


Individual particles with interesting properties can assemble to make new types of soft matter.

Slippery Particles

When liquid flows over a surface, the liquid layer next to the surface is usually considered stationary. In recent times, very small violations of this “no-slip boundary condition” have been measured for water on hydrophobic surfaces. The motion of a particle on flow should be affected if it has a slippery surface [1]. We are carrying out experiments to test this theory, and using molecular dynamics simulations to understand the implications for asymmetric Janus particles in flows [2] and in dimers [3].

Collective Dynamics

We can also study the dynamics of two or more interacting Janus spheres. We are especially interested in how these particles come together to form interesting out-of-equilibrium phases. In experimental work, we are trying to observe Janus colloids as they are brought together in a microfluidic system. Using molecular dynamics simulations, we can study these interactions and how they lead to clustering and dispersion under different conditions [4]. In theoretical work, we hope to model the phases and patterns which emerge in many-particle systems.


[1] Willmott, G. R. Slip-Induced Dynamics of Patterned and Janus-like Spheres in Laminar Flows. Phys. Rev. E 79, 066309 (2009).

[2] Safaei, S., Archereau, A. Y. M., Hendy, S. C. & Willmott, G. R. Molecular dynamics simulations of Janus nanoparticles in a fluid flow. Soft Matter 15, 6742-6752 (2019).

[3] Safaei, S., Hendy, S. C. & Willmott, G. R. Stability of amphiphilic Janus dimers in shear flow: a molecular dynamics study. Soft Matter 16, 7116 (2020).

[4] Safaei, S., Todd, C., Yarndley, J., Hendy, S. C. & Willmott, G. R. Asymmetric assembly of Lennard-Jones Janus dimers. Phys. Rev. E 104, 024602 (2021).


Location: Building 303, 38 Princes Street, Auckland, New Zealand
Phone: +64 9 373 7599 ext 89998
Email: g.willmott[at]auckland.ac.nz

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