Physical ageing of the contact line on colloidal particles at liquid interfaces

Kaz, David M.; McGorty, Ryan; Mani, Madhav; Brenner, Michael P.; Manoharan, Vinothan N.

doi:10.1038/nmat3190

Cited by 279 publications

(414 citation statements)

References 31 publications

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“…Alternatively, the contact line can be pinned by kinetic trapping at heterogeneities, roughness or other pinning sites on the particle surface [10,[14][15][16][17][18]. Curvature capillary migration depends on the coupling of the particle-sourced distortion with the host interface shape.…”

Section: Introductionmentioning

confidence: 99%

Curvature capillary migration of microspheres

2015

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We address the question: How does capillarity propel microspheres along curvature gradients? For a particle on a fluid interface, there are two conditions that can apply at the three phase contact line: Either the contact line adopts an equilibrium contact angle, or it can be pinned by kinetic trapping, e.g. at chemical heterogeneities, asperities or other pinning sites on the particle surface. We formulate the curvature capillary energy for both scenarios for particles smaller than the capillary length and far from any pinning boundaries. The scale and range of the distortion made by the particle are set by the particle radius; we use singular perturbation methods to find the distortions and to rigorously evaluate the associated capillary energies. For particles with equilibrium contact angles, contrary to the literature, we find that the capillary energy is negligible, with the first contribution bounded to fourth order in the product of the particle radius and the deviatoric curvature. For pinned contact lines, we find curvature capillary energies that are finite, with a functional form investigated previously by us for disks and microcylinders on curved interfaces. In experiments, we show microsphere migrate along deterministic trajectories toward regions of maximum deviatoric curvature with curvature capillary energies ranging from 6 × 10 3 − 5 × 10 4 kBT . These data agree with the curvature capillary energy for the case of pinned contact lines. The underlying physics of this migration is a coupling of the interface deviatoric curvature with the quadrupolar mode of nanometric disturbances in the interface owing to the particle's contact line undulations. This work is an example of the major implications of nanometric roughness and contact line pinning for colloidal dynamics.

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Section: Introductionmentioning

confidence: 99%

Curvature capillary migration of microspheres

2015

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“…Theoretical models based on continuum thermodynamics are well developed for idealized particle geometries 8,9 such as spheres, ellipsoids, or cylinders. Recent studies, however, point out significant limitations of such models in the presence of microscale features that are much smaller than the particle and are not considered by idealized geometric representations of the macroscale morphology 10,11 . These microscale features of physical or chemical nature can cause metastability 11 , which can lead to a very slow relaxation to equilibrium, or even the jamming of single particles at a non-equilibrium state.…”

Section: Introductionmentioning

confidence: 99%

Nanoparticles at liquid interfaces: Rotational dynamics and angular locking

Razavi

Kretzschmar

Koplik

et al. 2014

The Journal of Chemical Physics

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Nanoparticles with different surface morphologies that straddle the interface between two immiscible liquids are studied via molecular dynamics simulations. The methodology employed allows us to compute the interfacial free energy at different angular orientations of the nanoparticle. Due to their atomistic nature, the studied nanoparticles present both microscale and macroscale geometrical features and cannot be accurately modeled as a perfectly smooth body (e.g., spheres, cylinders). Under certain physical conditions, microscale features can produce free energy barriers that are much larger than the thermal energy of the surrounding media. The presence of these energy barriers can effectively "lock" the particle at specific angular orientations with respect to the liquid-liquid interface. This work provides new insights on the rotational dynamics of Brownian particles at liquid interfaces and suggests possible strategies to exploit the effects of microscale features with given geometric characteristics.

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“…Nevertheless, the results are consistent with a growing body of work showing -in the same, indirect way -that nanoscale heterogeneities do exist in colloids and are important for understanding their behaviour at fluid interfaces. In fact, recent experiments have shown that the attractive interactions between particles at interfaces 6 , as well as the relaxation rates of particles that breach an interface 7,8 , appear to be governed by surface defects. And because colloids typically have surface groups that keep the particles from aggregating, surface defects and contact-line pinning may be inherent features of colloidal systems.…”

Section: Vinothan N Manoharanmentioning

confidence: 99%