Abstract: A tissue expander device comprising a thin expandable cover and a concave base is disclosed. Together, the cover and the base form an envelope with a cambered interior chamber concave on the base and convex on the cover. The volume of the envelope is adjusted by introducing fluid into the chamber. As the device is inflated, the radius of curvature of the cambered base is gradually increased until the base becomes substantially planar when the device is fully inflated. Since the concave base becomes planar when the device is fully inflated, the surface of the device contacting the thin overlying skin is smooth and continuous thus reducing erosion of the skin flap by the edge of the base.