Capillary bridges play a important role for the stability of colloidal systems. The forces of these bridges strongly correlates with their shape. It is possible to measure capillary forces with an Atomic Force Microscope (AFM), but it is impossible with such a device to image the shape of the capillary bridge at the same time. Analytical and numerical calculations exist that correlates the force of the capillary bridges with the shape of the liquid . However experimentally capillary bridges couldn’t directly be imaged with the corresponding force in the micrometer range so far. A Laser Scanning Confocal Microscope (LSCM) can visualize the shape of a liquid bridge on solid surface in a three-dimensional form. Our aim is to bring both techniques, AFM and LSCM, together. Because the changes in shape of the menisci due to the force measurements with the AFM are in the range of µm/s, the LSCM must ensure a high image acquisition rate, which is possible to realize with a resonant scanner. We built a combined LSCM and AFM device and measured the forces with colloidal probes on liquid surfaces. In comparison to commercially available devices we are also able to image fast dynamics (up to 20 images per second).The combination of force spectroscopy and confocal microscopy allows us to image capillary bridges and simultaneously measure the corresponding force (Figure1) . We present the first results of simultaneous measurements of capillary bridges and the corresponding force curves.
Figure 1: Force Curve of a Colloidal Probe Measurement with Corresponding Confocal Images as Inset. a) Colloidal Probe approaches to the surface, b) Colloidal Probe touches the Liquid c) Colloidal Probe retracts from the liquid. Image Size of Confocal Images: 156μm · 68μm, Silica-Particle Diameter: 32μm, Liquid: Castor Oil.
