Microelectrodes and micromagnets. 1

Abstract

Two kinds of microelectrodes and one micromagnet have been perfected and used with very good results. 2 First, it was found that a platinum wire (No. 35, C.P.) inserted into a close-fitting quartz capillary can be drawn over a minute oxy-acetylene flame to a perfectly insulated needle-point less than one micron in diameter. Indeed, the platinum core in this exceedingly fine point may closely approximate the limits of microscopic vision.

The platinum wire at the opposite (undrawn) end extends a few mm. beyond the quartz capillary in order that the former may be annealed to an insulated copper wire of about the same diameter as that of the platinum wire and 2 feet in length. The drawing of the electrodes (see Fig. A, 1 and 2) and the annealing is readily done over the oxy-acetylene microburner (m.b.). About 3 mm. of the needle-tip of the electrode is bent over the flame, at right angles (Fig. A, 3) and the opposite end is sealed with deKhotinsky cement into a glass shank 5 mm. in diameter and 35 mm. long (Fig. A, 3, sh). This shank fits into the instrument-holder of a recently designed micro-manipulator. 3 By means of the latter the electrodes are operated with finest precision in a moist chamber on the stage of the microscope.

The second type of microelectrode is non-polarizable. For many purposes the platinum electrode would appear to be entirely satisfactory, but certain experiments make necessary the use of this second type. Peterfi 4 has recently described a microelectrode very similar to this one which has been in use for several months, so that his and mine were designed quite independently.