Construction of membrane sieves using stoichiometric and stress-reduced Si ₃N ₄/SiO ₂/Si ₃N ₄ multilayer films and their applications in blood plasma separation

The novelty of this study resides in the fabrication of stoichiometric and stress-reduced Si ₃N ₄/SiO ₂/Si ₃N ₄ triplelayer membrane sieves. The membrane sieves were designed to be very flat and thin, mechanically stressreduced, and stable in their electrical and chemical properties. All insulating materials are deposited stoichiometrically by a low-pressure chemical vapor deposition system. The membranes with a thickness of 0.4 μm have pores with a diameter of about 1 μm. The device is fabricated on a 6" silicon wafer with the semiconductor processes. We utilized the membrane sieves for plasma separations from human whole blood. To enhance the separation ability of blood plasma, an agarose gel matrix was attached to the membrane sieves. We could separate about 1 μL of blood plasma from 5 μL of human whole blood. Our device can be used in the cell-based biosensors or analysis systems in analytical chemistry.