An expandable breast implant eliminates the need for multiple procedures and injections and is also capable of self-administered or automatic expansion that is safe in any environment. The expandable breast implant design includes an upper matrix, a lower matrix, and a middle layer. The upper matrix comprises a plurality of cells containing a first reagent. The lower matrix comprises a plurality of wells containing a second reagent. The middle layer acts as a barrier between the upper matrix and the lower matrix. The middle layer may be activated and controlled to form openings. The first reagent from the cells in the upper matrix mixes with the second reagent from the wells in the lower matrix through the selected openings in the middle layer. The reagents react to form a gas that permeates through a hydrophobic membrane into an expandable shell to enlarge the breast implant.