Electrode puller

Place the carbon fiber-filled glass blank in the electrode puller and pull it into a microeiectrode. The glass should melt and contract around the fiber, finally breaking to leave an open pipet in one end of the puller and a pipet with a carbon fiber protruding from the glass at the other end (see Note 6 and Fig. 2A). 

About twelve micropipettes are pulled on a vertical electrode puller such that pipette lengths from shoulder to tip are about one centimeter with a uniform conical angle near the tip of the pipette. The micropipette tips are then broken off at about 40 microns in diameter. This is accomplished by loading a globule of glass onto the microforge wire such that it surrounds the wire (Figure 4a). 

The procedure for the fabrication of the Pt submicroelectrodes is shown in Fig. 3.16 (Slevin etal. 1999). Namely, Step I Seal of Pt microwire (Fig. 3.16a). The Pt microwire with 50 pm diameter was mounted in a glass capillary, which was drawn to a fine point using a pipette puller with 3-5 mm microwire protruded from the tip of glass capillary. Step II Etching Pt microwire (Fig. 3.16b). The protruded Pt wire was electrochemically etched by applying 1.2 V potential between the Pt wire and the counter electrode. The etching procedure was finished when the current decreased to zero. Step III Microwire insulation (Fig. 3.16c). Insulating paint... 

These companies supply equipment for microscopy and electrophysiology including amplifiers, micromanipulators, electrode holders, reference electrodes, pipet pullers, and microelectrodes. 

Electrodes are pulled on a Sutter P-97 Flaming/Brown micropipet puller. Tips are generally 2-3 pm in diameter, and resistances are 3-6 MQ. 

Before removing the electrode from the puller, use a pair of fine scissors to cut the protruding carbon fiber (which may be several centimeters long) back to a cm or so beyond the end of the glass at the tip of the micropipet. This is easily done without magnification. 

This procedure can also be applied to 5 and 10 pm platinum and gold wires (where the use of soft glass capillaries is sometimes preferred). For smaller tips (1-2 pm diameter), a Wollaston wire (a metal wire covered by a silver layer) is first placed in weak nitric acid solution to dissolve the silver layer prior to sealing the tip (Section 6.3.2). A laser puller can also be used with small diameter quartz capillaries to make submicron size electrodes (Section 6.3.3). Such sealing techniques require much practice and patience. 

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