This letter describes the formation of two-dimensional (2D) crystals of dipolar particles (TN) made of electrostatically charged, joined, millimeter-scale Teflon (T) and nylon-6,6 (N) spheres, and the separation of these crystals, as a distinct phase, from a mixture of TN and similar, capacitively charged particles that were coated with gold (Au2). The extent of separation increased with increasing amplitude of agitation, and with decreasing density of particles. Above a threshold in the amplitude of agitation, the crystals broke apart and the particles remixed. This system is a 2D model of the nucleation of crystals of polar molecules in a polarizable liquid.
Bibliographical noteFunding Information:
This research was supported by the DOE (DE-FG05-00ER45852). The NSF (CHE-0518055), DARPA/ARO (W911NF-04-1-0170), and the Xerox Corporation provided support for salaries. We thank Professor Z. Suo and X. Zhao for helpful discussions, D. Co, T. Hanisco, and D. Wilmouth for assistance with the construction of the apparatus, the NSF and MRSEC for a stipend through Grant No. DMR-0213805 (G.K.K.), as well as the support of EMBO and HFSP (M.R.), the American Cancer Society (S.W.T.), and the NIH (B.F.S.) for postdoctoral fellowships.