Fabrication Of Paper-Based Microfluidic Devices By UV Degradation Of Self-Assembling Layer And Its Application

Microfluidic paper-based analytical devices (μPADs), as a burgeoning research field, possess attractive features such as low-cost, portable, easy-to-use, easy-to-fabricate, bio-compatible compared to the conventional microfluidic devices fabricated with silicon, glass, and poly materials, μPADs combine the advantages of microfluidic technology and paper. By patterning hydrophilic and hydrophobic microfluidic channels and microstructures on paper, micro total analytical systems are fulfilled featured with the miniaturization, integration and portability. μPAD also provides a new platform for microfluidic analysis. This work aims at to develop a novel fabrication method of paper-based microfluidic devices and study the applications of uPAD in food quality and health diagnostics.The thesis is composed of three parts:In chapter1, recent progress in the microfluidic paper-based analytical devices are reviewed. First, several techniques for fabrication of μPADs have been introduced, including photolithgraphy, wax printing and dipping, plasma treatment, ink printing, ink jet etching, plotter printing and hand plotting, flexography printing, ect. The advantages and disadvantages of various fabrication techniques were also investigated. Second, a various detection methods such as colorimetric assay, electrochemical (EC) detection, electrochemiluminescence (ECL) and chemiluminescence were introduced. Third, we also summarized its application areas such as in health diagnostics, environmental monitoring and food quality control.In chapter2, This work presents a novel and facile method for fabricating paper-based microfluidic devices by means of coupling of hydrophobic silane to paper fibers followed by deep UV-lithography. After filter paper being simply immersed in an octadecyltrichlorosilane (OTS) solution in n-hexane, the hydrophilic paper became highly hydrophobicdue to the hydrophobic OTS molecules were coupled to paper’s cellulose fibers. The hydrophobized paper was then exposed to deep UV-lights through a quartz mask that had the pattern of the to-be-prepared channel network. Thus, the UV-exposed regions turned highly hydrophilic whereas the masked regions remained highly hydrophobic, generating hydrophilic channels, reservoirs and reaction zones that were well defined by the hydrophobic regions. The optimal immersing time, OTS concentration and the time of UV/O3treatment were investigated. The optimal immersing time, OTS concentration and UV/O3treatment time were5min,0.1%and90min, respectivly. The hydrophilic-hydrophobic pattern on the filter paper was very stable. After the patterned paper was stored at ambient temperature for6months or more, the hydrophilic-hydrophobic contrast remained the same as its initial status. Furthermore, the patterns could survive from being immersed in organic solvents such as ethanol, acetone, n-hexane and methylene chloride for at least24h. The dynamic resolution for hydrophilic channels was233±30μm and that for between-channel hydrophobic barrier was137±21μm. XPS and ATR-FT-IR spectroscopes were employed to characterize the surface chemistry of the OTS-coated and UV/03-treated paper, and the related mechanism was discussed.In chapter3, the developed paper-based microfluidic devices presented in chapter2was used to colorimetric assays of nitrite in red cebilose and glucose and BSA assay. The NO2-content in sample determined by the proposed μPAD method agreed well with the concentration determined by ion chromatograph.