Adjunct material and methods of using adjunct material to reinforce tissue in proximity to a staple line are provided herein. In general, the adjunct material can be used to maintain a seal in tissue, such as lung tissue, and prevent stapled tissue from tearing. This adjunct material can be coupled to a jaw of a surgical stapler, and can be deployed into tissue along with the staples. In some embodiments, the adjunct material can comprise an outer material encompassing an inner, hydrophilic swellable material. The outer material can be selectively dissolvable and/or absorbable. When the outer material is punctured by staples or otherwise penetrated, moisture is passed to the inner material which then swells and expands to transition to a predetermined shape to seal the tissue and prevent leaks from forming in the tissue. Portions of the inner material around the staple line can transition to a large radius.
