A method of controlling macroscopic strain of a porous structure includes contacting a porous structure with a modifying agent which chemically adsorbs to a surface of the porous structure and modifies an existing surface stress of the porous structure. A device in one embodiment includes a porous metal structure, which when contacted with a modifying agent which chemically adsorbs to a surface of the porous metal structure, exhibits a volumetric change due to modification of an existing surface stress of the porous metal structure; and a mechanism for detecting the volumetric change. Additional methods and systems are also presented.
 The United States Government has rights in this invention pursuant to Contract No. DE-AC52-07NA27344 between the United States Department of Energy and Lawrence Livermore National Security, LLC for the operation of Lawrence Livermore National Laboratory.