Light driven diffusioosmosis : the manipulation of colloids using azobenzene containing surfactant The emergence of microfluidics created the need for precise and remote control of micron sized objects. I demonstrate how light sensitive motion can be induced at the micrometer scale by a simple addition of a photosensitive surfactant which makes it possible to trigger hydrophobicity with light. With point like laser irradiation radial inward and outward hydrodynamic surface flows are remotely switched on and off. In this way ensembles of microparticles can be moved toward or away from the irradiation center. Particle motion is analyzed according to varying parameters such as surfactant and salt concentration illumination condition surface hydrophobicity and surface structure. The physical origin of this process is the so called light driven diffusioosmosis (LDDO) a phenomenon that was discovered in the framework of this thesis and is described experimentally and theoretically in this work. To give a brief explanation a focused light irradiation induces a local photoisomerization that creates a concentration gradient at the…