Typical configurations of weakly charged silica spheres at the interface between fresh deionized water and air. Particle size serves as a scale bar.

Click the picture to see the movie of particle motion at the water-air interface. The particles feel Coulomb repulsion at short distances so that they seldom get very close to each other. Their spatial configurations appear random. You may stop the movie at any time to view the intermediate particle configurations.

Typical configurations of weakly charged silica spheres at the interface between salty water (15 mM NaCl) and air. Particle size serves as a scale bar.

Click the picture to see the movie of particle motion at the salty-water-air interface. The particles experience a short-range attraction so that they often come near each other (compared to the no salt case). You may stop the movie at any time to view the intermediate particle configurations. One sees transient chain-like structures more clearly by repeated pause and play of the movie. The formation of these fluctuating chain-like structures is a hallmark of weak dipolar fluids.