[Paper Review] Clogging and Jamming of Colloidal Monolayers Driven Across a Disordered Landscape

R. Stoop, Pietro Tierno|arXiv (Cornell University)|Dec 14, 2017

Diatoms and Algae Research3 citations

TL;DR

This study experimentally investigates clogging and jamming in a monolayer of paramagnetic colloids driven across a quenched disordered landscape of fixed obstacles. Using tunable magnetic dipolar interactions, the authors demonstrate that anisotropic attraction reduces clogging and enhances flow, while quenched disorder strongly amplifies the 'faster is slower' effect, revealing a key role for both disorder and inter-particle interactions in microscale transport dynamics.

ABSTRACT

We experimentally investigate the clogging and jamming of interacting paramagnetic colloids driven through a quenched disordered landscape of fixed obstacles. When the particles are forced to cross a single aperture between two obstacles, we find an intermittent dynamics characterized by an exponential distribution of burst size. At the collective level, we observe that quenched disorder decreases the particle ow, but it also greatly enhances the "faster is slower" effect, that occurs when increasing the particle speed. Further, we show that clogging events may be controlled by tuning the pair interactions between the particles during transport, such that the colloidal ow decreases for repulsive interactions, but increases for anisotropic attraction. We provide an experimental test-bed to investigate the crucial role of disorder on clogging and jamming in driven microscale matter.

Motivation & Objective

• To understand how quenched disorder in a disordered landscape affects clogging and jamming in driven microscale systems.
• To investigate the role of tunable pair interactions between colloidal particles in controlling collective transport and clogging dynamics.
• To experimentally test the 'faster is slower' (FIS) effect in a system with controlled disorder and interaction tuning.
• To explore the connection between clogging and jamming in pinned, disordered systems using a model colloidal system.

Proposed method

• Paramagnetic colloids (2.8 µm diameter) are driven across a uniaxial ferrite garnet film (FGF) with a periodic magnetic stripe pattern using a rotating magnetic field.
• Quenched disorder is introduced via 5 µm silica particles irreversibly attached to the FGF, creating a spatially uncorrelated obstacle landscape.
• The effective dipolar interaction between colloids is tuned in situ by adjusting the in-plane magnetic field amplitude $H_x$, enabling control over repulsive or anisotropic attractive interactions.
• The interaction potential is modeled as $U_d = \alpha[H_x^2(1+3\cos 2\vartheta) - 2H_z^2]/r^3$, with $\alpha$ dependent on particle susceptibility and FGF parameters.
• Particle trajectories and velocities are tracked via video microscopy, and mean speed $\langle v_x \rangle$ is measured as a function of driving frequency and $H_x$.
• Clogging dynamics are analyzed through burst size distributions and velocity fluctuations, with focus on intermittent flow and collective behavior.

Experimental results

Research questions

• RQ1 How does quenched disorder in a disordered landscape affect the collective transport and clogging of driven colloidal monolayers?
• RQ2 To what extent does the 'faster is slower' (FIS) effect emerge and intensify in the presence of quenched disorder?
• RQ3 How do tunable dipolar interactions—specifically anisotropic attraction—alter clogging and flow efficiency in this system?
• RQ4 Can the formation of particle bridges and clogs be controlled by engineering inter-particle interactions in a disordered environment?

Key findings

• The presence of just 8% obstacle area fraction ($\Phi_o = 0.08$) reduces particle speed by up to 45% when driving frequency increases from 6.3 to 50.3 rad/s, demonstrating a strong enhancement of the 'faster is slower' effect by disorder.
• Anisotropic dipolar interactions at $H_x = 1.8H_z$ induce a flexible, elongated train-like structure that slides plastically through obstacles, increasing normal velocity fluctuations ($\delta v_y = 1.15\ \mu\text{m/s}^{-1}$) and enhancing flow compared to repulsive interactions.
• For repulsive interactions ($H_x = 0.4H_z$), increased inter-particle distance reduces flow efficiency, with mean speed decreasing due to larger effective packing fraction $\Phi_m$.
• The system exhibits exponential burst size distributions in intermittent flow, indicating a critical-like behavior near clogging transitions.
• Magnetic dipolar interactions are strong ($U_d \sim 2-95\ k_B T$) and dominate over thermal and electrostatic effects, enabling effective in situ tuning of particle interactions.
• The experimental setup provides a controllable test-bed for studying clogging and jamming transitions in disordered, driven systems, with direct relevance to microfluidics and active matter.