The Tatt2away Tattoo Removal System (US Patent 8,663,162) works using a similar technique to how a tattoo is applied:

The skin is lightly abraded in a patented pattern to reduce scarring
A patented solution developed by Rejuvetek Medical called TEPRSOL
is introduced instead of ink. TEPRSOL produces an escharotic response in the skin that relies on the body’s natural healing response to reject the ink from the body in the form of a scab, actually removing the ink from the body. Tatt2Away treatments are designed to remove the tattoo in a series of visits for maximum results.

The number of treatments depends on the size complexity, and location of the design.An average size tattoo (4 inches by 4 inches), may need four or five visits but is realistically determined during the initial consultation.
Discomfort from the procedure is comparable to that of a tattoo being applied. Treatment
sessions last about 20-30 minutes and time between treatment sessions is usually about six-eight weeks.