Automated, high-resolution micropipet aspiration reveals new insight into the physical properties of fluid membranes

We describe recent advances in our experimental approach to examine the physical properties of biological and artificial membranes by automated micropipet aspiration. New instrumentation allows us to apply fast yet precise tension protocols to membranes while continuously recording the membrane deformation with high-speed videomicroscopy. Robust algorithms for subpixel geometric measurements track the displacements of membrane edges with resolution of a few nanometers and enable us to determine changes of the membrane area and enclosed volume of pipet-aspirated cells or vesicles with exceptional accuracy. Experimentation and data analysis are greatly facilitated by custom-written software whose basic design is described here as well. Example measurements demonstrate how this technique has significantly improved the amount and reliability of data obtained by various types of micropipet-aspiration experiments, allowing us to study interesting aspects of membrane behaviour that have eluded earlier techniques.