| Polydimethylsiloxane（PDMS）is a kind of silicone rubber with good flexibility and corrosion resistance.However,PDMS has natural hydrophobicity,low surface polarity,easy to adsorb impurities and other defects.This limits its further development in the fields of microfluidics,bonding,and flexible substrates.The use of plasma technology to modify PDMS into a hydrophilic surface can expand its application range.However,this hydrophilic property is unstable and easily degrades to a hydrophobic state in a short time,and the mechanism is not yet clear.Therefore,this article explores the hydrophobic properties of PDMS surface.The factors affecting the wettability before and after microwave plasma modification of PDMS were analyzed,and the PDMS was irreversibly bonded to the glass sheet.The orthogonal test table was used to obtain the best bonding process parameters.Finally,a molding method is used to prepare a flexible SERS substrate,and nano-silver is used as an enhancement factor to perform rapid and repeated detection of melamine aqueous solution.The specific work is as follows:Firstly,an innovative microwave plasma experimental system with two-dimensional precise scanning was built.The system is composed of plasma power module,nozzle and positioning module,and pattern two-dimensional scanning module.The large-area cyclic scanning of the sample by microwave plasma is realized by the electric high-precision two-dimensional displacement platform,which improves the processing efficiency.The hydrophilic modification of PDMS showed that the contact angle of PDMS decreased with the increase of microwave air plasma treatment time.When the RF power of the plasma reaches 60 W to 80 W,the treatment time is 50 s,which is the best modification process parameter.Secondly,using the constructed microwave plasma experimental system,under atmospheric pressure,changing the radio frequency power and processing time of nitrogen plasma to explore the hydrophobicity recovery of PDMS.The change of PDMS contact angle before and after modification was measured by static water contact angle.The morphology of the modified surface was analyzed by metallurgical microscope and scanning electron microscope,and the changes of functional groups before and after modification were analyzed by infrared spectroscopy.The results show that the contact angle of PDMS after microwave nitrogen plasma treatment is about 103°.Within a certain range,with the increase of RF power and processing time,the recovery of PDMS hydrophobicity becomes slow.However,when the radio frequency power and processing time reach a certain value,the PDMS surface structure will be destroyed,wrinkles and cracks will appear on the surface,and amino functional groups will be generated.The internal low-molecular-weight polymer（LMW）diffuses to the surface of PDMS,covering the hydrophilic surface,and accelerating the recovery of PDMS hydrophobicity.Finally,an oxygen plasma cleaner was used to realize the irreversible bonding of PDMS and the glass sheet to prepare a flexible SERS substrate.Explore the best bonding process parameters through orthogonal experiments.The results show that the main factor that affects the bonding area percentage effect is the gas flow rate,followed by the processing time,and the power is the smallest.When the power is 100 W,the processing time is 90 s,and the gas flow rate is 30 sccm,it is the best bonding area percentage,which can reach 98.23%.The micro-fluidic pipes of the SERS substrate were prepared by molding method,and the nano-silver particles prepared by the hydrothermal synthesis method were coated into the micro-fluidic pipes using a pulling device,and finally achieved a pair of10-2 mol/L and 10-3 mol/L Rapid and repetitive detection of melamine aqueous solutions.Figure[47]Table[12]Ref.[85]... |
