An Instrument for the Production of Microelectrodes Used in Electrophysiological Studies

The membrane potential of single muscle fibers may be measured using an internal microelectrode of tip diameter less than 0.5μ. Previously such microelectrodes could only be prepared manually and this method has certain disadvantages. The problem has been overcome through the use of an instrument for which details of design, construction, and operation are given. In principle, a 35-mm length of Pyrex tubing of outside diameter 2 mm and inside diameter 1.3 mm is heated from a surrounding electrically energized platinum coil. At the start, 100-g force is applied to the tubing in the longitudinal direction by means of a solenoid and plunger arrangement. As the tubing softens its length is extended by 5 mm whereupon the automatic application of 1700-g force draws the tubing apart thus forming two micropipettes. The dimensions and electrolytic resistance of typical microelectrodes manufactured with the aid of the instrument are presented.