Monopolar (also called Unipolar)
Monopolar or unipolar refers to a device having one pole or electrode.
With monopolar delivery, the current from the generating machine flows through the body from a single electrode (handpiece) and meets maximum resistance in the area around the tip of the handpiece, where tissue heating in the subdermal layers then occurs. A grounding, or “return pad” may also be used, attached to the patient’s lower back or abdomen, to provide a low resistance path for the current to flow back to the generating machine, to complete the electrical circuit.
An example of a monopolar RF only device used for facial rejuvenation and available in the UK is Thermage.
Biopolar
Biopolar refers to a device having two poles or electrodes.
With bipolar delivery, the current from the generating machine flows only through the tissue which is between the two electrodes on the handpiece; these electrodes start and complete the electrical circuit. Hence, with bipolar delivery, no current flows through the rest of the body, so no grounding or return pad is needed.
In all cases of radiofrequency delivery types, it is the resistance to the current flow in the tissue, not the electrode that generates the heating effect.