Fabrication of extremely fine glass micropipette electrodes

Abstract

Glass micropipette electrodes with extremely fine tips and high mechanical rigidity have been fabricated with a semi-automatic pipette-puller. The fabrication involves a two stage pull of a heated glass capillary held horizontally by a pair of non-slip clamps. Air is automatically blown from symmetrically located nozzles on to the softened portion of the capillary at the onset of the second pull. With this technique micropipettes with a relatively short taper and large cone angle at the very tip are produced, which not only possess high mechanical rigidity, but also a fineness at the tip (500 Å or less). A special advantage of the large cone angle at the tip is that such an electrode has a much lower electrical impedance than a conventional micropipette electrode with a comparable tip diameter. The size and shape of the micropipette can be easily altered to meet the specific need. The principle of differential vapour pressure has been utilized to fill the micropipettes with the desired electrolytes. A vibration technique for inserting a microelectrode into living cells is also described.