A colloidal particle (upper left (a), red) is trapped by optical tweezers (upper left (b)) as a surrounding colloidal suspension (upper left (a), blue) flows past. Surprisingly long-range order develops in the particle density (lower left, dark bands are regions with over-representation of particles; s is the particle diameter). A novel analysis of particle motions using a technique from computer science reveals the otherwise hidden flow patterns in the fluid surrounding the probe (right). Collaboration between the research groups of Aaron Dinner, Norbert Scherer, and Stuart Rice at the University of Chicago MRSEC.
J. Pesic, J. Z. Terdik, X. Xu, Y. Tian, A. Lopez, S. A. Rice, A. R. Dinner, and N. F. Scherer, Phys Rev E 86, 031403 (2012). DOI:10.1103/PhysRevE.86.031403