Tissue expanding device and method of making same

Claim 1

A skin expanding device comprising: a substantially non-extensible base; an expansion layer joined to the periphery of the base defining an expansion chamber when fluid is introduced between the base and the expansion layer; means for introducing fluid between the base and the expansion layer; and wherein the expansion layer includes only first and second area portions, the first area portion being 50% to 300% thicker than the second area portion such that when fluid is introduced between the expansion layer and the non-extensible base, the first area portion expands proportionally differentially from the second area portion, both area portions expanding as fluid is being introduced, the expansion layer and base initially being flat in a non-expanded state so that the expansion layer is in contact with the base throughout the layers' entire area so that neither base nor layer has any folds or wrinkles when in the non-expanded state.