This method was invented by Elizabeth Fozzard, a needle electrologist, in 1959. The hair is held in the tweezer and the RF energy is transmitted through the moist area of the hair bulb and papilla causing it to coagulate. Subsequent knowledge has proven this concept incorrect.
Radio frequency is a heating current.
The RF tweezer heats the hair where the tweezer legs touch the hair. This heat is produced by the water molecules spinning around inside the hair in response to the alternating current. Friction heat is produced inside the hair. The hair continues to get hotter and hotter at this point of contact. The heated hair cells are in contact with other cells that are cooler and the heat is transferred to these cooler cells all the way down the hair shaft.