Dry beveling of micropipette electrodes.

Beveling or otherwise modifying the tips of micropipettes has been found to improve their performance. Although some success has been reported, especially with wet beveling methods, problems and uncertainties are significant. In this paper we describe both manual and automated dry beveling systems which use a bevel table and bevel plate similar to those in wet beveling schemes. However, instead of using electrode impedance changes as a guide to the shape and size of electrode tips, we monitor beveling with a piezoelectric crystal which detects the minute vibrations of the electrode as the tip scrapes the bevel plate. The filtered output of the crystal indicates the progress of the grinding operation and allows the process to be controlled. Precise control of electrode tip movement is accomplished through use of a Kopf model 607B motorized hydraulic microdrive, amenable to both automated and manual control. The whole process can be followed by non-destructive electron microscope (E.M.) examination of electrode tips. Dry beveling combined with E.M. examination of electrode tips allows a much more precise determination of optimal electrode tip size and shape than is at present possible with wet beveling.