Introduction to colloidal dispersions in external fields

Progress in the research area of colloidal dispersions in external fields within the last years is reviewed. Colloidal dispersions play a pivotal role as model systems for phase transitions in classical statistical mechanics. In recent years the leading role of colloids to realize model systems has become evident not only for equilibrium situations but also far away from equilibrium. By using external fields (such as shear flow, electric, magnetic or laseroptical fields as well as confinement), a colloidal suspension can be brought into nonequilibrium in a controlled way. Various kinds of equilibrium and nonequilibrium phenomena explored by colloidal dispersions are described providing also a guide and summary to this special issue. Particular emphasis is put on the comparison of real-space experiments, computer simulations and statistical theories.Comment: 11 pages, 2 figures, Eur. Phys. J. Special Topics (accepted

Active Colloidal Molecules

Like ordinary molecules are composed of atoms, colloidal molecules consist of several species of colloidal particles tightly bound together. If one of these components is self-propelled or swimming, novel "active colloidal molecules" emerge. Active colloidal molecules exist on various levels such as "homonuclear", "heteronuclear" and "polymeric" and possess a dynamical function moving as propellers, spinners or rotors. Self-assembly of such active complexes has been studied a lot recently and this perspective article summarizes recent progress and gives an outlook to future developments in the rapidly expanding field of active colloidal molecules