A wound dressing has a micro-architecture to produce appropriate strains in cells to promote the healing a wound. The apparatus includes a wound cover for defining a reservoir over a wound in which a negative pressure may be maintained by forming a substantially fluid-tight seal around the wound, a vacuum source in fluid communication with the reservoir and suitable for providing an appropriate negative pressure to the reservoir to stimulate healing of the wound, and a porous structure positioned in contact with the wound for delivering micro-mechanical forces to localized areas of the wound. The porous structure comprises a three-dimensional film material having directional apertures formed therein.