dynamics and manipulation of single molecules in liquids
diffusion of single molecules in a thin liquid film on a glass substrate
(left) single molecule trajectories at in a liquid at a surface step
(right) diffusion anisotropy in different spatial areas of the surface
manipulation of liquids in a shear flow - we have developed an analysis technique which allows the separation of shear induced motion and diffusion in single molecule tracking experiments
the symmetry of interactions in the liquid is destroyed at an interface to a solid. this as well as the interaction of the liquid with the solid cause structural and dynamical differences to the bulk liquid such as the liquid layering - a near order effect which shows up as monomolecular layers of a liquid parallel to the solid surface. we study the dynamics of individual (dye) molecules in such liquid nanostrutures by means of wide field fluorescence microscopy. this technique allows real time observation and tracking of single molecules. as a special unique technique we employ surface steps to monitor out of plane motion from solid surfaces - something which is typically not possible in simple single molecule tracking experiments.
the group develops analysis techniques allowing to monitor spatially resolved dynamical properties. this allows to characterize anisotropic motion of single dye molecules in heterogeneous environments and opens the way to correlate structure and dynamics at chemically heterogeneous surfaces.
liquids between two solid surfaces are able to reduce the friction between solids by orders of magnitude. the way a liquid acts as lubricant, which part of the liquid really feels the presence of the solid and how structure in the liquid and friction are connected on a microscopic scale is the subject of this project. to explore these topics as well as phase transitions/stick-slip transition of liquids close to surfaces, we have coupled a surface forces apparatus (sfa) to a single molecule wide field microscope. this allows the detection of the motion of individual molecules in the confinig gap of the sfa even under non-equilibrium conditions. this gives the first time a powerful technique at hand to manipulate liquid films or even macro-molecules in a confing gap and simultaneously watching the motion.
manipulation of liquids by surface properties - the dynamics of liquids is influenced by the local chemical properties of the solid surface as displayed for a freshly cleaved mica surface with different ion distribution
this is our surface forces apparatus capable of tracking single dye molecules in confined liquid films
