Inkjet-Printed Microfluidic Multianalyte Chemical Sensing Paper

ArticleinAnalytical Chemistry 80(18):6928-34 · September 2008with109 Reads
DOI: 10.1021/ac800604v · Source: PubMed
Abstract
This paper presents an inkjet printing method for the fabrication of entire microfluidic multianalyte chemical sensing devices made from paper suitable for quantitative analysis, requiring only a single printing apparatus. An inkjet printing device is used for the fabrication of three-dimensional hydrophilic microfluidic patterns (550-mum-wide flow channels) and sensing areas (1.5 mm x 1.5 mm squares) on filter paper, by inkjet etching, and thereby locally dissolving a hydrophobic poly(styrene) layer obtained by soaking of the filter paper in a 1 wt % solution of poly(styrene) in toluene. In a second step, the same inkjet printing device is used to print "chemical sensing inks", comprising the necessary reagents for colorimetric analytical assays, into well-defined areas of the patterned microfluidic paper devices. The arrangement of the patterns, printed inks, and sensing areas was optimized to obtain homogeneous color responses. The results are "all-inkjet-printed" chemical sensing devices for the simultaneous determination of pH, total protein, and glucose in clinically relevant concentration ranges for urine analysis (0.46-46 muM for human serum albumin, 2.8-28.0 mM for glucose, and pH 5-9). Quantitative data are obtained by digital color analysis in the L*a*b* color space by means of a color scanner and a simple computer program.
    • "In addition, it has the advantage of miniaturization. In recent years, microfluidics has been used in various applications such as bioassays, blood analysis, and controlling manufacturing quality [20][21][22][23][24]. Recent studies on microfluidics have been expanded to fluid-tunable radio frequency (RF) systems and fluid detection microwave systems [24,25]. "
    [Show abstract] [Hide abstract] ABSTRACT: In this paper, a novel flexible tunable metasurface absorber is proposed for large-scale remote ethanol sensor applications. The proposed metasurface absorber consists of periodic split-ring-cross resonators (SRCRs) and microfluidic channels. The SRCR patterns are inkjet-printed on paper using silver nanoparticle inks. The microfluidic channels are laser-etched on polydimethylsiloxane (PDMS) material. The proposed absorber can detect changes in the effective permittivity for different liquids. Therefore, the absorber can be used for a remote chemical sensor by detecting changes in the resonant frequencies. The performance of the proposed absorber is demonstrated with full-wave simulation and measurement results. The experimental results show the resonant frequency increases from 8.9 GHz to 10.04 GHz when the concentration of ethanol is changed from 0% to 100%. In addition, the proposed absorber shows linear frequency shift from 20% to 80% of the different concentrations of ethanol.
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    • "Further, a liver function mPAD was developed to semiquantitate the level of aspartate aminotransferase (AST) and alanine aminotransferase (ALT) for drug-related hepatotoxicity monitoring in resource-limited settings [26] . mPADs are similar to lateral flow assays in that they are inexpensive, equipmentfree , and can be used for colorimetric visualization, but also include the capability to multiplex and can be scaled-up with different microfabrication methods such as photolithography [25], inkjet etching [30], plasma etching [31], and wax printing [32]. Although these manufacturing methods seem more complicated than fabrication of lateral low-based assays, mPADs are still regarded as one of the ideal [ and others [33][34][35][36]. "
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    • "Recent years have witnessed an increasing number of novel and low-cost fabrication approaches being proposed to address these issues. Inkjet printing, a low-cost rapid additive manufacturing technique, has been recently introduced in the microfluidics fabrication process [11], [12]. Most prior research efforts of inkjet-printed microwave sensors/tunable elements [12]–[16] took advantage of the inkjet-printing technique only for sealing the microfluidic channels and patterning the conductive structures , but they still required other subtractive manufacturing techniques such as laser etching to fabricate the channels. "
    [Show abstract] [Hide abstract] ABSTRACT: This paper demonstrates the first-of-its-kind additively manufactured microfluidics-based flexible RF sensor, combining microfluidics, inkjet-printing technology, and soft lithography, which could potentially enable the first "real-world" wearable "smart skin" applications. A low-cost, rapid, low-temperature, and zero-waste fabrication process is introduced, which can be used to realize complex microfluidic channel networks with virtually any type of sensing element embedded. For proof-of-concept purposes, a reusable and flexible microfluidics sensor was prototyped using this process, which only requires 0.6-μL fluid volume to produce a 44% frequency shift between an empty (ϵr=1) and a water-filled channel (ϵr=73), demonstrating a sensitivity that is higher than most previously reported microfluidics-based microwave sensors. Seven different fluids were used to measure the sensitivity of the prototype and an overall sensitivity of 24%/log(ϵr) was observed. The "peel-and-replace" capability of the presented sensor not only facilitates the cleaning process for sensor reusability, but it also enables sensitivity tunability. For bent/conformed configurations, the sensor's functionality is good even for a bending radius down to 7 mm, demonstrating its great flexibility. After bending multiple times, the sensor still exhibits a very good performance repeatability, which verifies its reusability feature. The introduced additively manufactured RF microfluidics-based sensor would be well suited for numerous wearable and conformal fluid sensing applications (e.g., bodily fluids analyzing and food monitoring), while it could also be utilized in a variety of microfluidics-reconfigurable microwave components.
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