By Suhas Dhenge

 To study the electrical activity of individual cell microelectrodes are employed.  This type of electrode must be small with respect to the cell dimensions to avoid causing serious cellular injury and thereby changing the cell’s behavior.  Also this type of electrode must be strong so that it can penetrate the cell membrane and remain mechanically stable.

 Diameter of tip - ranging from approximately 0.05 to 10 micrometer.  Microelectrode can be formed from solid-metal needles, from metal contained within of on the surface of a glass needle, or from a glass micropipet having a lumen filled with an electrolytic solution.

 Metallic.  Glass micro capillaries.

 The metal microelectrode is essentially a fine needle of a strong metal that is insulated with an appropriate insulator up to it’s tip.  A metal needle is prepared in such way as to produce a very fine tip. This is usually done by electrolytic etching.  Suitable strong metals for these microelectrodes are stainless steel, platinum-iridium alloy and tungsten.  A metal micro electrodes are used in direct contact with the biological tissue and therefore have a lower resistance.

 Tungsten is preferred for constructing micro electrodes due to it’s mechanical strength and it’s apparent inertness.  The electrode is frequently a silver wire prepared with an electrolytic AgCl surface. Platinum and stainless steel wires are also occasionally used.

 Glass micropipet electrodes are fabricated from special grade Pyrex glass capillaries. These micro capillaries are usually filled with a electrolyte.  The central region of piece of capillary tubing is heated with a burner to the softening point.  They improve stability can be obtain by properly choosing the metal and the electrolyte.  It has a substantial current carrying capacity because of the larger surface contact area between the metal and electrolyte.

GLASS MICROELECTRODE