Centrifugal Microfluidic Chip With Differential Surface Treatment And Its Application In The Preliminary Application For Protein Detection

Centrifugal microfluidic chip-based platforms are an important tool in analytical chemistry and biomedical technologies due to their high integration,low cost and robust operation.In recent years,they have been widely used in clinical diagnosis,biochemical reactions,food testing,and environmental monitoring.However,traditional flow control methods,such as external pumps,valve structures,and integrated microvalve devices,are difficult to be applied in the flow control operation of the centrifugal microfluidic chip.The unidirectional flow of the fluid induced by the rotation of the centrifugal chip and the nature of the overall movement of the chip have limited the handling of the flow control in the centrifugal chips and their applications.Surface property is an important factor that affects the fluid movement on micro-scale structures,which has attracted much attention due to its easy fabrication and integration.Therefore,this thesis designed a centrifugal microfluidic chip with different hydrophilic treatment of the siphon channels to control the liquid flow within the chip.Based on the designed chips,the flow control abilities of different surface treatments have been studied,and their preliminary application in protein detection has been investigated.Firstly,this thesis introduced the liquid driving theory of the centrifugal microfluidic chip,including the centrifugal force on the liquid and the capillary force based on the surface tension.A two-dimensional model was constructed using Comsol Multiphysics 5.5 software to analyze the liquid flow within the capillary channels with different contact angles.The results have shown that when the contact angle is between15° and 60°,the liquid flow in the capillary channel is faster,which provides a guidance for hydrophilic treatment methods.Subsequently,according to the simulation results,the hydrophilic treatment strategies for the PMMA surface,plasma treatment,and hydrophilic agent treatment including TWEEN-20,Triton X-100 and PEG400,were chosen and analyzed.The hydrophilic properties of the treated surfaces were characterized by the contact angle measurement method.With these different treated surfaces,the on-chip liquid transfer and the absorbance detection were used to compare the differences in microfluid control of different treating methods.Finally,based on the requirement of the fluid control for the centrifugal microfluidic chip,TWEEN-20 and Triton X-100 with a volume fraction of 2.0%were selected as the hydrophilic treatment methods for different siphon channels on the chip.The widely used protein detection was selected to explore the preliminary application of the centrifugal chip in this study.The siphon valve structures of different hydrophilic degrees were used to control the orderly flow of various reaction reagents in the protein detection experiment on the centrifugal microfluidic chip.Based on the Lowry protein detection method,a centrifugal microfluidic chip was designed and fabricated.Different hydrophilic treatments on specific siphon channels were applied.For different concentrations of plasma and whole blood samples,liquid transfer and detection applications were carried out on the chip.Subsequently,the plasma concentration was detected.The protein concentration in the centrifugal microfluidic chip showed a good linear relationship between the absorbance and the concentration in the concentration range of 0.1%to 1.0%.In the preliminary experiment,there was a difference between the on-chip detection result and the reference value.The possible reason was that the hydrophilic reagent has an influence on the reaction system.After modification of the hydrophilic treatment method,the R~2 for the linear fit between the on-chip detection results and the traditional method detection results reached 0.9831,indicating that the two detection methods are very comparable.The detection results of whole blood samples showed that after the whole blood samples were diluted to the volume concentrations of 1.0%,2.0%,and 4.0%,respectively,the on-chip protein detection values were all within the reference range.In that way,the qualitative and semi-quantitative analysis of the whole blood sample were achieved.