A hydrodynamic filter (100, 110, 115, 120, 130) comprising: a first portion that comprises a first and second protrusions (30, 40) protruding in a first direction; and a second portion that is spaced apart from the first portion to face the first portion and comprises a third and fourth protrusions (35, 45) protruding in a second direction facing the first direction to correspond to the plurality of protrusions of the first portion, a first capturing portion that is formed by the first protrusion and the third protrusion; a second capturing portion that is formed by the first protrusion, the second protrusion, the third protrusion and the fourth protrusion, and wherein the first protrusion and the second protrusion that are spaced apart from each other, and the third protrusion and the fourth protrusion that are spaced apart from each other and respectively face the first protrusion and the second protrusion, and wherein the first protrusion and the third protrusion are flexible, so as to form a structure into which a fluid and target molecules are introducible; wherein a first distance between the first protrusion and the third protrusion ranges from 5 μm to 100 μm, and wherein a second distance between the second protrusion and the fourth protrusion ranges from 5 μm to 100 μm, and wherein the first distance between the first protrusion and the third protrusion is greater than the second distance between the second protrusion and the fourth protrusion such that target molecules are captured in the hydrodynamic filter and only the fluid exits from the hydrodynamic filter; wherein a space between the first protrusion and the second protrusion and a space between the third protrusion and the fourth protrusion has curved surfaces (50, 55), respectively; wherein the first protrusion and the third protrusion are tapered toward ends thereof. a first portion that comprises a first and second protrusions (30, 40) protruding in a first direction; and a second portion that is spaced apart from the first portion to face the first portion and comprises a third and fourth protrusions (35, 45) protruding in a second direction facing the first direction to correspond to the plurality of protrusions of the first portion, a first capturing portion that is formed by the first protrusion and the third protrusion; a second capturing portion that is formed by the first protrusion, the second protrusion, the third protrusion and the fourth protrusion, and wherein the first protrusion and the second protrusion that are spaced apart from each other, and the third protrusion and the fourth protrusion that are spaced apart from each other and respectively face the first protrusion and the second protrusion, and wherein the first protrusion and the third protrusion are flexible, so as to form a structure into which a fluid and target molecules are introducible; wherein a first distance between the first protrusion and the third protrusion ranges from 5 μm to 100 μm, and wherein a second distance between the second protrusion and the fourth protrusion ranges from 5 μm to 100 μm, and wherein the first distance between the first protrusion and the third protrusion is greater than the second distance between the second protrusion and the fourth protrusion such that target molecules are captured in the hydrodynamic filter and only the fluid exits from the hydrodynamic filter; wherein a space between the first protrusion and the second protrusion and a space between the third protrusion and the fourth protrusion has curved surfaces (50, 55), respectively; wherein the first protrusion and the third protrusion are tapered toward ends thereof.