Research Of The Point-Of-Care Testing Chip Channel Hydrophilic And Hydrophobic Modification Technology

The polymer microfluidic chips because of its low fabrication cost,high analytical performance,solvent consumption,and the advantages of good biological compatibility have gotten widespread attention.It’s not enough to drive the liquid flow forward that only rely on the surface tension of the chip material itself.Based on this,the hydrophilic coating is used to enhance the surface hydrophilicity of specific thermoplastic microfluidic chips.And the problem of edge effect caused by hydrophilic modification is solved.The main contents of this paper are as follows:(1)Based on the basic infiltration theory,the surface contact angle of rectangular channel capillary flow and the sol ratio were optimized and calculated.In this paper,the capillary flow theory is described.The liquid flow rate control theory was calculated according to the channel size and physical properties of the experimental chips and the surface hydrophilic treatment of the contact angle range was estimated of 30-35°initially.Through the experimental demonstration,the best ratio of sol-gel system for this chip was prepared.(2)The hydrophilic coating process of POCT chips had been proposed and improved.The processing platform was built and debugged,and the process parameters were determined by experiments.The design and production of the specific chip fixture based on the experimental POCT chip was finished.The process parameters were experimentally explored and optimized by using the pulling device.It is known from the experimental results that the pulling speed and the temperature did not have a great influence on the film formation while the viscosity of the sol was relatively small.The results show that it has good adhesion between the hydrophilic coating and the substrate,and the film thickness is in the order of 100 nanometers,which does not affect the microstructure of the chip surface.The inter-chip difference and the differences between chips of contact angle after hydrophilic coating is small.The serum flowing rates meet the theoretical calculations and testing requirements,and the flowing rates are stable after hydrophilic coating.(3)The formation mechanism of edge effect was analyzed and the solution was proposed and the process parameters were studied.Adopting the method of hydrophobic scribing on the side wall and bottom surface to eliminate the condition of corner flow and eliminate the edge effect.In this experiment,the solutions of hydrophobic marking line are liquid paraffin,silicone oil and neutral resin.And considering the hydrophobicity,the scope of application and the viscosity of the solution,silicone oil is selected as the hydrophobic marking line solution.Experiments demonstrate the effect of hydrophobic marking line width on the liquid flow.While the silicone oil was used as the solution of hydrophobic marking line and the range of marking line width was 60-90 μm,the radius of curvature of the liquid front is 0.29 mm-0.87 mm and it showed a stable convex liquid front.Fluorescence test results showed that after the hydrophilic coating and hydrophobic marking line,the peak values of cardiac troponin I(cTn I)were all above 25000,and the surface treatment methods can be used for cTnI testing.