What technique uses an electric current to force water-soluble substances into the skin?

Iontophoresis is the technique that uses an electric current to facilitate the penetration of water-soluble substances into the skin. This process involves the application of a topical solution to the skin, followed by the use of a mild electric current to drive the active ingredients deeper into the epidermis. The electric current alters the permeability of the skin and enhances the absorption of the substances, which can lead to improved efficacy of the ingredients being delivered, such as vitamins or medications.

The other methods listed do not utilize electric currents for substance delivery. Dermabrasion and microdermabrasion are procedures focused on the physical exfoliation of the skin, helping to improve texture and appearance through the removal of dead skin cells. Ultrasound therapy employs sound waves rather than electric currents to promote healing or product absorption, but it does not specifically involve forcing water-soluble substances into the skin.