An apparatus comprising a first substrate having a first surface, a second substrate having a second surface facing the first surface and an array of metallic raised features being in contact with the first surface to the second surface, a portion of the raised features having a mechanical bend or buckle plastic deformation produced therein via a compressive force. One or more of the metallic raised features has one or more surface singularities therein prior to the mechanical bend or the buckle plastic deformation produced by the compressive force.