Abstract: A check valve for a fluidic system includes a fluidic conduit having an inlet with a first particle barrier, an outlet with a second particle barrier and a fluid chamber between the inlet and the outlet; and at least one particle disposed in the fluid chamber, the particle or particles aggregating at the first particle barrier to form a first hydrodynamic resistance when a first fluid pressure at the inlet is less than a second fluid pressure at the outlet, the particle or particles aggregating at the second particle barrier to form a second hydrodynamic resistance when the first fluid pressure is greater than the second fluid pressure.

Abstract: A portable hand-held blood sampling device having a self-filling capability includes a blood separation filter. The filter has a plurality of pores sized to permit passage of selected blood constituents such as blood plasma through the device. The device has a separated blood conduit that extends beyond the outlet of the device and is shaped for easy penetration into a self-sealing septum of a blood analyzer. An annular shield extends from the device outlet beyond the conduit to prevent inadvertent contact of the conduit by a user.