Experimental Study On Adhesive Ability Of PDMS Chips And Microextraction System

The research of microfluidic chip becomes the hot spot with its miniature, highly effective, fast, and low consumption. The Polydimethylsiloxane(PDMS)is widely applied in the casting of microfluidic chips. The emphases of present investigation are the got-up technology and the liquid-liquid (L-L) extraction system of PDMS microfluidic chips. The study is of highly theoretical significance and practical value in the on-line environment monitoring.The stickup performance of PDMS chip is of important practical value to the microfluidic chip. The key parameters influencing the chip bonding are studied in this paper. The key parameters are the ratio of PDMS prepolymer to curing agent, the curing temperature and time, the material of curing mould and the treatment of ultraviolet radiation. The optimal bonding condition for microfluidic chips is obtained. It is found that the bonding intensity is greatly affected by the material of curing mould. For the three materials studied here, the bonding intensity of chips is greatly affected by the material of curing mould under the same conditions. For understanding the reason, the surface properties of PDMS plates casted by three moulds of glass, PMMA and plastic are measured by AFM and XPS. The results of AFM show the surface roughness of PDMS plate casted by glass mould is the largest, that casted by plastic mould is in the middle, and that casted by PMMA mould is the smallest. Meanwhile, the results of XPS spectrum indicate that there is no chemical process on the surface of PDMS plate during casting by different moulds. It is concluded that the surface roughness of PDMS plates is the most important factor to the bonding intensity of PDMS chips.The liquid-liquid (L-L) extraction on the microfluidic chips is realized here. The effects of key factors such as velocity, the ratios of two phases velocity, liquid molecular polarity, the hermetic instance of miniaturized channel, the surface tention of the liquid surface, the shape width and the surface character of miniaturized channel on the L-L interface are investigated. The liquid-liquid extraction system is estabilished and three processes of microextraction are successful observed. The diffusion-line concept is proved by experiments again, and Zn ions on-line micro-extraction is confimed to be diffusion controlled process.