Cooperative microlenses.
We demonstrate that microspheres above a substrate act as microscopic lenses. Their Brownian motion causes the focal point to change abruptly, thereby creating characteristic intensity fluctuations which depend on the interaction between the spheres. To this end, superparamagnetic spheres in a magnetic field assemble into long pearl chains, where the intensity fluctuations depend on the stiffness of the chain. Upon assembling the superparamagnetic beads into a two-dimensional colloidal crystal, the fluctuations are restricted in two dimensions, and temporal network structures develop.
Helseth
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L
Fischer
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