Body-cavity electrodes

Four-electrode systems are commonly used on humans both with skin surface electrodes or on probes meant for different body cavities. It could also be used by implantable devices... 

Incorporate the neodymium magnet into the body of the paste of graphite-epoxy composite, 2 mm under the surface of the electrode [1] and continue placing the paste until filling all the cavity. Cure the conducting composite at 40°C during 1 week. Once the resin is hardened, polish the surface first with abrasive paper and then with alumina paper. 

FIGURE 2.1 Three-dimensional view of the cluster beam source (not to scale). The body of the source is sectioned to show the electrodes arrangement in the cavity. Note the asymmetric placement of the gap. 

It consists of a ceramic cubic body, in which a cylindrical cavity is drilled. A channel is drilled perpendicular to the axis of the cavity and hosts two rods (electrodes) of the material to be vaporized, facing each other and separated by a gap of about 1 mm. A solenoid pulsed valve injects helium at the pressure of 20 bar through an insulating ceramic nozzle on the back of the cavity. The gap between the electrodes is off-axis, in such a way that the gas flushes on the cathode surface. A removable nozzle with cylindrical shape closes the front of the source. 

A catheter tip or probe electrode is placed in a naturally occurring cavity in the body, such as in the gastrointestinal system. A metal tip or segment on a catheter makes up the electrode. In the case where there is no hollow lumen, the catheter or probe is inserted into the cavity so that the metal electrode makes contact with the tissue. A lead wire down the lumen of the catheter or down the center of the probe connects the electrode to the external circuitry. Multiple electrodes can be placed along the probe as illustrated in Figure 4.5a. 

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