Many properties of solids, such as colloid stability, adhesion, interfacial energy, wettability and bio-compatibility are determined by their surface properties as charge, roughness and chemical composition and can be modified by thin adsorption layers.
Therefore the measurement of the interaction forces gives important information about the surfaces and the effect of adsorbed ions or molecules. In our surface forces laboratory, we measure interaction forces in the presence of air, vapor and solutions in a distance range of nanometers up to some micrometers.
Most of the force measurement are done with the scanning probe microscope (SPM or AFM).
With standard SPM tips, imaging of the surface topography and spatially resolved force measurements can be done at the same time (force-volume mode). For a quantitative evaluation of interaction forces, the colloid probe technique is applied: The sharp SPM tip is replaced by a spherical colloidal particle of a few micrometers size. The colloidal probe technique allows not only the elimination of the probe geometry but also the application of a variety of materials (e.g. polymers) as force probes and the measurement of weak interactions. Forces between chemically modified surfaces are investigated by chemical force microscopy . With the AFM, not only vertical but also lateral (friction) forces can be determined. The devices are equipped with fluid cells and heating stages to enable force measurements in liquids or at elevated temperatures. With the Multimode SPM, force measurements can be done under defined environmental conditions (temperature, humidity, composition of the atmosphere) using an environmental chamber. The bimorph surface forces apparatus (MASIF) is a device especially designed for the measurement of interaction force in air and liquids. It measures the forces between two macroscopic spheres or a sphere and a flat. In comparison to the SPM, the parameters of the force measurement can be adjusted in more detail and lower forces can be detected. The surface forces laboratory rooms provide a temperature and humidity controlled environment and clean room conditions.
The surface forces laboratory is located in the basement of the new laboratory building, which was completed in 1996. The consist of a temperature and humidity controlled preparation (L02) and measurement room (L01).