PDMS Selective Bonding for the Fabrication of Biocompatible All Polymer NC Microvalves

Microvalves are commonly used in microfluidic systems to control precisely the liquid flow. In this paper, the design and fabrication of a normally-closed (NC) all-polymer membrane-type microvalve is described. The microvalve with a diameter and thickness of 5 mm and 3 mm, respectively, is fabricated completely in biocompatible polydimethylsiloxane (PDMS). The opening pressure, which depends on the adhesion between the membrane and the slab, is reduced to the noticeably low value of 3.4 kPa by the surface oxidation of the PDMS layers. This technique in combination with a selective bonding by Polyethylene terephthalate (PET) shadow masking allows for the fabrication of a high reverse pressure microvalve (no flow up to 0.6 MPa reverse pressure). Other major fabrication steps include PDMS doctor-blading and soft lithography in order to fabricate the thin and surface patterned membranes, respectively. The presented microvalve features a minimum flow rate of 1.0 ml min^-1.