Inkjet-Printed Microfluidic Multianalyte Chemical Sensing Paper

ArticleinAnalytical Chemistry 80(18):6928-34 · September 2008with109 Reads
DOI: 10.1021/ac800604v · Source: PubMed
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]. "
    [Show abstract] [Hide abstract] ABSTRACT: Point-of-care (POC) diagnostics play an important role in delivering healthcare, particularly for clinical management and disease surveillance in both developed and developing countries. Currently, the majority of POC diagnostics utilize paper substrates owing to affordability, disposability, and mass production capability. Recently, flexible polymer substrates have been investigated due to their enhanced physicochemical properties, potential to be integrated into wearable devices with wireless communications for personalized health monitoring, and ability to be customized for POC diagnostics. Here, we focus on the latest advances in developing flexible substrate-based diagnostic devices, including paper and polymers, and their clinical applications.
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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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