Fabrication method of two-level polymeric microstructure with the help of deep X-ray lithography

Two- or multi-level microstructures are getting more important in several applications such as multi-component micro optical elements and various microfluidic systems. In the present study, a simple and efficient method is newly proposed for a fabrication of the two-level polymeric microstructures. Making a mother two-level microstructure consists of two processes: (1) the hot embossing process for a fabrication of microstructures on a PMMA substrate, and (2) the deep X-ray lithography using the hot embossed substrate for a high aspect ratio microstructure fabrication, resulting in a high aspect ratio microstructure containing smaller microstructures on its surface. Making use of so fabricated two-level microstructures as a mother structure, one could achieve a mass replication of the same microstructures via injection molding process with a metallic mold insert obtained by a nickel electroforming onto the mother microstructure. In order to demonstrate the proposed method, a polymeric high aspect ratio microstructure having smaller square microstructures on its top surface was fabricated. The fabricated two-level microstructure shows fine vertical sidewalls, which is a characteristic feature of the deep X-ray lithography. In addition, a metallic mold insert for a mass replication was fabricated by a nickel electroforming process.