Methanol- and ethanol-induced convex deformation and macrovoid formation in poly(methyl methacrylate) (PMMA) through sandwich structures, consisting of polycarbonate (PC)/PMMA/PC was investigated. The sandwich structures had a circular hole on the outer PC layer, which allowed the solvent to contact with PMMA. Both single-convex and double-convex deformations of the PMMA layer were produced, depending upon the hole diameter. For a fixed hole diameter, there was an optimum PMMA thickness, which produced maximum curvature for the double-convex deformation. The physical mechanism for these phenomena can be well explained by the relative strength of the swelling stress and the deformation resistance of the PMMA layer. We also used the wet phase-inversion method to produce porous convex deformation for the sandwich structures. The size, number, and location of the convex pores can be prescribed. This may have potential applications in local filtering and other areas. (C) 2004 Wiley Periodicals, Inc.