Studies On Key Processes And Techniques Of PDMS Microfluidic Chips

Poly(dimethylsiloxane)(PDMS) is an unique class of polymers that can be crosslinked to form elastomer with many attractive properties, including ease of fabrication, high thermal stability, excellent optical characteristics and biocompatibility. It has been used in fabricating microfluidic chips. As a hydrophobic material, however, PDMS has very inert surface properties, such as poor wettability and weak adhesion, so it is necessary for PDMS to modify its surface properties. Some key processes such as the microfabrication of PDMS microfluidic chips and surface modification methods were presented in this paper.Fabricating processes of PDMS microchip were studied according to its molecule structure and characteristics. Based on the process of PDMS membrane, flow character of spin coating was discussed, and the relation of the membrane thickness with rotate speed was achieved. Cast molding and replica molding were used to fabricate PDMS membrane. It showed that the chip fabricated has several advantages such as high reproduction and surface roughness.Two surface modification techniques of UV oxidation and oxygen plasma were researched in order to improve the wettability of PDMS surface. The surface hydrophilicity was identified by means of drop shape analyzer(DSA) and X-ray photoelectron spectroscopy(XPS), and the optimal parameters were obtained through the analysis, also the effect of parameters on the stability of the modified PDMS surface was tested, moreover, the modified principle was carried out by XPS.Permanent bonding methods of PDMS microfluidic chips were studied, including two-step process and oxygen plasma. Peel strength and SEM tests were carried out to discuss the bonding effects of the two methods. The experimental results showed that the two-step process can be applied for low pressure, oxygen plasma was the strong bonding strength, so the bonded chips can endure high pressure. The respective bonding principle was discussed.