超大表面积自驱动微流控芯片的设计与制备

Objective: A new material with ultra-large surface area named nano-forest is preparedby Micro-Electro-Mechanical System(MEMS) processing technology. Based on this material, anew microfluidic chip for point-of-care test with simple operation, rapid detection and highsensitivity is created. Methods: The fabrication of nano-forests in micro-channel on quartzsubstrate mainly includes: cleaning and drying of quartz substrate; spinning polyimide(PI) coating;re-spinning phenolic resin photoresist on PI coating; photolithography to expose the channel;treating the PI layer with oxygen plasma and argon plasma to synthesize nano-fiber forestsstructure; nano-fiber-quartz nanoforests are realized by using nano-fiber forests as nanomasks inanisotropic etching of quartz by using reactive ion etching (RIE); the micro-channel withnano-forests structure inside is achieved after removing upper nanofiber forests structure andphenolic resin photoresist coating.The height, width, density and specific surface area ofnano-forest are studied and analyzed by scanning electron microscope(SEM). Optical properties are tested by ultraviolet-visible spectrophotometer. The driving force is characterized by the flowrate of PBS solution.The sensitization effect is evaluated by saturated fluorescence test throughantibody and AbFluor 680 dye-labeled secondary antibody. The sample pad, bond pad, micro-channel with nano-forests structure, nitrocellulose membrane and absorbent material areassembled on PMMA substrate in sequence, which is the microfluidic chip. The chip based on thesandwich format with a polyclonal antibody and a AbFluor 680 dye-labeled secondary antibody isused to detect ricin toxin(RT). Results: The scanning electron microscope shows that the nanofiberforests structure is formed on quartz substrate after oxygen plasma and argon plasmabombardment. The single nanofiber is upright on the substrate with a diameter of about 50-100 nm, a height of 1.8 um and a density of about 20/m2. The quartz nano-forests structure can beobtained after RIE with nano-fibre forests structure as mask and resist removal. The singlestructure is shaped like a cone. The diameter of the cone bottom is about 100-200 nm, the height isabout 1.0 um, the density is about 10/m2, and the surface area to bottom area is more than 5:1. Self-driven test provides information of the flow rate of PBS is to be about 5 mm/s in themicro-channel on the basis of nano-forests structure. The transmittance of the channel is 89.5%at680 nm wavelength. It shows that the channel has good transmittance, which makes the loss ofexcitation light or emission light much less, and is conducive to the sensor capturing more signals. With same surface modification, the planar quartz structure has shortcomings of short lasting effecttime and low saturation fluorescence intensity. To the contrary, nano-forests structure withultra-large surface area has a good sensitization effect in the test. RT can be detected sensitivelybased on the significantly fluorescent intensity.The linear range of detection is from 10 pg/mL to6250 pg/mL and the limit of detection (LOD) is lower than 10 pg/mL. Conclusion: Thenano-forests structure with good optical properties reduces the requirements of sensor and alsomakes the choice of fluorescent dyes wider.The three-dimensional structure of the nano-forest hasan ultra-large surface area, which increases the amount of antibody compared to the planarstructure, and thus improves the sensitivity of detection greatly. Compared with theimmunochromatographic test strip, the microfluidic chip has an advantage of high sensitivity, thusthe quantitative analysis can be realized within a certain range. Most microfluidic chips requirecomplex equipments to provide driving force, which will make them costly and bulky. Driven bythe capillary force, the chip with nano-forests structure inside makes the detection simple and fast. Combined with the miniaturized detection terminal, the platform can be miniaturized, portable, and automated, achieving the goal of simple, fast and efficient analysis. These characteristics makethe chip an ideal candidate for the development of rapid detection methods.