Hydrophilic PEO-PDMS for microfluidic applications

• Published in: Journal of micromechanics and microengineering 2012-02, Vol.22 (2), p.25012-6
• Main Authors: Yao, Mingjin, Fang, Ji
• Format: Article
• Language: English
• Subjects: Adhesive bonding; Applied fluid mechanics; Applied sciences; Binding; Bioengineering; Condensed matter: structure, mechanical and thermal properties; contact angle; Devices; Exact sciences and technology; Fluid dynamics; Fluidics; Fundamental areas of phenomenology (including applications); Glass; hydrophilicity; Instruments, apparatus, components and techniques common to several branches of physics and astronomy; lab-on-a-chip; Mechanical engineering. Machine design; Mechanical instruments, equipment and techniques; Medical; Medical devices; Microfluidics; Micromechanical devices and systems; PDMS; PEO; Physics; Polydimethylsiloxane; Precision engineering, watch making; Silicone resins; Solid-fluid interfaces; surface modification; Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties); Wetting
• ISSN: 0960-1317; 1361-6439
• DOI: 10.1088/0960-1317/22/2/025012

Polydimethylsiloxane (PDMS) is a popularly used nontoxic and biocompatible material in microfluidic systems, which is relatively cheap and does not break easily like glass. The simple fabrication, optical transparency and elastomeric property make PDMS a handy material to work with. In order to develop different applications of PDMS in microfluidics and bioengineering, it is necessary to modify the PDMS surface nature to improve wetting characteristics, and to have a better control in nonspecific binding of proteins and cells, as well as to increase adhesion. At the moment, the hydrophilic surface modification performance of PDMS is known to recover its hydrophobicity shortly after oxidation modification, which is not stable in the long term (Owen and Smith 1994 J. Adhes. Sci. Technol. 8 1063-75). This paper presents a long-term stable hydrophilic surface modification processing of PDMS. The poly(dimethylsiloxane-ethylene oxide polymeric) (PDMS-b-PEO) is used in this project as a surfactant additive to be added into the PDMS base and the curing agent mixture during polymerization and to create hydrophilic PEO-PDMS. The contact angle can be controlled at 21.5-80.9° with the different mixing ratios and the hydrophilicity will remain stable for two months and then slightly varied later. We also investigate the bonding conditions of the modified PDMS to a silicon wafer and a glass wafer. To demonstrate its applications, we designed a device which consists of microchannels on a silicon wafer, and PEO-PDMS is utilized as a cover sheet. The capillary function was investigated under the different contact angles of PED-PDMS and with different aspect ratios of microchannels. All of the processes and testing data are presented in detail. This easy and cost-effective modified PDMS with a good bonding property can be widely used in the capillary device and systems, and microfluidic devices for fluid flow control of the microchannels in biological, chemical, medical applications.