A microfiltration patch for capturing selected viable tumor cells from a fluid sample comprising: a top porous membrane having top membrane pores extending vertically through the top porous membrane from an upper surface of the top porous membrane to a lower surface of the top porous membrane; a bottom porous membrane having bottom membrane pores, extending vertically through the bottom porous membrane from an upper surface of the bottom porous membrane to a lower surface of the bottom porous membrane, wherein several of the bottom membrane pores are distributed in the bottom porous membrane to be horizontally offset from several of the top membrane pores distributed in the top porous membrane, so that the portion of the bottom membrane located directly beneath said several top membrane pores is entirely solid and the portion of the top membrane located directly above said several bottom membrane pores is solid; a gap separating the top porous membrane from the bottom porous membrane, which gap is defined by a planar space between the lower surface of the top porous membrane and the upper surface of the bottom porous membrane, wherein the gap comprises the planar space between said several top membrane pores and said several bottom membrane pores; wherein the gap distance between the lower surface of the top porous membrane and the upper surface of the bottom porous membrane is equal over the area defined by the gap and larger than non-tumor cells, molecules and/or components not to be captured by the microfiltration patch, wherein the top membrane pores and bottom membrane pores have diameters greater than diameters of blood cells and smaller than diameters of circulating tumor cells and wherein the gap distance is smaller than the diameters of the circulating tumor cells, and wherein the top membrane pores have a size from 3 μm to 15 μm. a top porous membrane having top membrane pores extending vertically through the top porous membrane from an upper surface of the top porous membrane to a lower surface of the top porous membrane; a bottom porous membrane having bottom membrane pores, extending vertically through the bottom porous membrane from an upper surface of the bottom porous membrane to a lower surface of the bottom porous membrane, wherein several of the bottom membrane pores are distributed in the bottom porous membrane to be horizontally offset from several of the top membrane pores distributed in the top porous membrane, so that the portion of the bottom membrane located directly beneath said several top membrane pores is entirely solid and the portion of the top membrane located directly above said several bottom membrane pores is solid; a gap separating the top porous membrane from the bottom porous membrane, which gap is defined by a planar space between the lower surface of the top porous membrane and the upper surface of the bottom porous membrane, wherein the gap comprises the planar space between said several top membrane pores and said several bottom membrane pores; wherein the gap distance between the lower surface of the top porous membrane and the upper surface of the bottom porous membrane is equal over the area defined by the gap and larger than non-tumor cells, molecules and/or components not to be captured by the microfiltration patch, wherein the top membrane pores and bottom membrane pores have diameters greater than diameters of blood cells and smaller than diameters of circulating tumor cells and wherein the gap distance is smaller than the diameters of the circulating tumor cells, and wherein the top membrane pores have a size from 3 μm to 15 μm.