title: Crystallization and chain formation in liquid drops.
abstract: Colloidal crystals are easily formed in liquid drops and thin films upon evaporation. In this study we use spherical paramagnetic beads, which make it possible to manipulate them by an external magnetic field. We show that the hydrophilic beads position themselves at a distance from the contact line so that they barely touch the water-air interface. Upon applying a magnetic field, the magnetic beads can either arrange themselves in a two-dimensional repulsive lattice or form attractive vertical chains, depending on the contact angle of the drop. We also demonstrate that the vertical chains' position from the contact line is quantized and depends on the number of beads in the chain.
authors.affiliation: Max Planck Institute of Colloids and Interfaces, D-14424 Potsdam, Germany.
authors.forename: L E
authors.initials: LE
authors.lastname: Helseth
authors.forename: T M
authors.initials: TM
authors.lastname: Fischer