Fabrication of Paper-based Microfluidic Devices by Plasma Treatment and Its Application in Glucose Determination

Abstract

Currently, various methods for fabricating microfluidic paper-based analytical devices (μPADs) have been proposed due to their great potential applications in many fields such as clinical diagnosis, food quality control and environmental monitoring. Hereby, a novel and simple method for the fabrication of microfluidic paper-based analytical devices via plasma treatment is reported. Paper was first hydrophobized via octadecyltrichlorosilane (OTS) silanization. The OTS silanized paper was then region-selectively plasma-treated via a mask with channel network. The plasma-exposed area of the paper was turned to hydrophilic channel network due to the degradation of hydrophobic OTS molecules coupled to the paper's cellulose fibres before. Two types of hybrid polymethylmethacrylate-polydimethylsiloxane (PMMA-PDMS) masks were developed to obtain well defined hydrophilic channel with the required depth. With the elastic PDMS piece adhered to the rigid PMMA piece, it excellently solved the problem of the expansion of hydrophilic channel caused by the leakage of plasma atmosphere in the gap between the mask and paper. The effect of plasma-treating time on hydrophilicity of paper was investigated. The water contact angle (WCA) dramatically decreased from 133.9°±1.3° to 0° with the prolonging of the plasma treating time from 0 s to 30 s. Meanwhile, the depth of wettable channel could also increase to nearly the thickness (180 μm) of the paper after treated for 30 s. Attenuated total reflectance Fourier transformed infrared (ATR-FT-IR) spectrometer and X-ray photoelectron spectroscopy (XPS) were applied to characterize the surface chemistry of paper during silanization and plasma treatment, and the related mechanism was discussed. The fabricated μPAD was applied for detection of plasma glucose in whole blood. After diluted with 2% NaCl by a ratio of 1∶4, plasma could be separated from blood cells due to their different mobility in the channel on paper. The separated plasma reached test readout zone and reacted with the substrates of Trinder's reaction. The analytical results observed with the μPAD-based colorimetric assays agreed well with those determined by conventional glucose meter.

Emerging Designs of Electronic Devices in Biomedicine

“…They have the ability to perform laboratory operations on micro-scale, using miniaturized equipment, and can be fabricated by using 2-D [86][87][88] or 3-D [89,90] methods to transport fluids in both horizontal and vertical dimensions, depending on complexity of the diagnostic application. The principal techniques in the literature for fabrication of paper-based microfluidic devices include: wax printing [90], inkjet printing [91], photolithography [92], flexographic printing [93], plasma treatment [94], laser treatment [95], wet etching [96], screen printing [97], and wax screen printing [98]. The µPADs can be used with the naked eye for qualitative testing but can also be used as quantitative assays based on specific detection methods.…”

Plasmon-Based Colorimetric Nanosensors for Ultrasensitive Molecular Diagnostics

“…Since the LSPR is markedly influenced not only by interparticle distance, shapes and sizes of plasmonic nanostructures, but also by the interface and surrounding mediums, the aggregate/dispersion state of plasmonic nanoprobes is susceptible to external stimulus in complicated environments, such as the existence of high salt and other interfering substrates Otherwise, because of the large surface area of nanomaterials, other impurities were usually nonspecifically adsorbed during the sensing events, which leads to false detection signals. Although specific surface chemistry using antifouling agents like bovine serum albumin and polyethylene glycol could resist surface fouling in practical use, there still remain many challenges. , For instance, polyethylene glycol molecules are subjective to auto-oxidation in biological fluids and thereby unsatisfactory for long-term clinical use. , Reecently, some novel surface chemistries including the use of zwitterionic molecules have been developed, suggesting that there would be useful ways for issuing these problems in the plasmonic nanomaterial-associated colorimetric assays …”

“…Although specific surface chemistry using antifouling agents like bovine serum albumin and polyethylene glycol could resist surface fouling in practical use, there still remain many challenges. 136,137 For instance, polyethylene glycol molecules are subjective to auto-oxidation in biological fluids and thereby unsatisfactory for long-term clinical use. 42,137 Reecently, some novel surface chemistries including the use of zwitterionic molecules have been developed, suggesting that there would be useful ways for issuing these problems in the plasmonic nanomaterial-associated colorimetric assays.…”

Paper-based assays for urine analysis

“…The hydrophobic molecules in the unmasked portions of the paper undergo degradation, thus uncovering the hydrophilic paper underneath. 98 After plasma treatment of OTS-silanized paper, the contact angle between water and the hydrophilic channel was measured to be 0 , representing full contact, while the contact angle of water on the hydrophobic region was 133.9 þ/À1.3 . 98 Furthermore, the water not only made full contact with the hydrophilic channel but could also penetrate fully through the thickness of the paper within only 30 s.…”