A microelectrode is a very tiny electrode, small enough to be inserted into an individual cell to monitor neural signals or bring about tissue stimulation.
Microelectrodes work by conducting electrical signals through small glass capillaries filled with a conductive solution, such as potassium chloride. Silver wires that are coated with silver chloride can also be used for this purpose.
A microelectrode tip is so small, often less than one micrometer in diameter, that it can penetrate the plasma membrane of a cell without causing damage. Differences occurring in the cell, while in the resting or active state, can be detected by the microelectrode and transmitted to a measuring device, such as an oscilloscope. Dissolved oxygen, pH and ion levels can also be detected and relayed by the microelectrode.
While they can be used individually, microelectrodes are also used in an array format. Multiple units can be inserted into different individual cells.
A practical example of this technology is found in microelectrode recording. This allows neurosurgeons to accurately identify the best location to implant deep brain simulators used in the treatment of Parkinson's disease. Other neurostimulators implanted into the body, such as cochlear implants and pacemakers, also make use of microelectrodes.