Experimental Study On Fabrication Of PDMS And Microextraction System

The research on microfluidic chip, which is a kind of micro-total analysis systems (μTAS), now represents the developing direction in analysis instruments field. The fabrication process of microfluidic chip with polydimethylsiloxane (PDMS) material and the on-line liquid-liquid (L-L) micro-extraction technology are studied in details. As an application example of above micro-extraction technology, Zn ions on-line separation on microfluidic chip is investigated in this dissertation.In the first part, the core problems such as the design principles, casting micro-fabrication method, seal technology and surface modification of PDMS are discussed for PDMS microfluidic chip. The effects of the proportion of PDMS and curing agent, the curing temperature and time on the bonding strength of PDMS wafers are investigated. The optimized conditions for PDMS chip bonding are obtained and testified by experiment. UV radiation is applied to modify the surface of PDMS-fabricated microfluidic replica to improve its hydrophobic property and adhesion between PDMS plates. It is found that hydrophobic and adhesive properties are greatly improved after the due time and strength of radiation.In the second part, the on-line L-L micro-extraction is studied. Zn ions are separated on-line successfully by the micro-extraction technology. The effects of key factors such as the surface tension of the liquid-liquid interface, fluid viscosity, molecular polarity, the shape, width and surface roughness of extraction channel (EC), velocity and velocity ratios of the two phases, diffusion distance, the specific interface area (the interface-to-volume ratio), air bubble, hydrophobic surface of PDMS, reaction speed, reactant concentration, interfering ions and pH, etc. on the efficiency of micro-extraction procedure, especially, on stabilization of L-L interface are investigated. Some effective ways to improve the performance of micro-extraction are outlined. The proposed"diffusion-line"hypothesis is proved by experiments, and Zn ions on-line micro-extraction is confirmed to be diffusion controlled process for the first time.