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  • In the hollow channels the capillary force is used to


    In the hollow channels, the capillary force is used to transport multiphase fluidics, such as whole blood or colloidal suspensions that contains particulates. We believe that this type of channels will become the basis for low-cost, portable, and technically simple multiphase flows. We demonstrate this capability by the simultaneous transportation of colloidal suspensions that contain particulates and whole flood. The channel system is small, disposable, easy to use (and carry), and requires no external equipment, reagents, or power sources. We believe this kind of system is attractive for use in less industrialized countries, in the field, or as an inexpensive alternative to more-advanced technologies already used in clinical settings [11–14].
    Materials and methods We combined hollow channel and paper channel as shown in Fig. 1. First we paste transparent adhesive tape on the top of glass slide layer by layer. Then we used a laser craft cutter (Han\'s laser marking machine DP-H50L) to carve micro-channels into multilayer transparent adhesive tape. Finally we put a strip chromatography paper on the top of the micro-channel and sealed with transparent adhesive tape to form the device (Fig. 1).
    Results and discussion
    Acknowledgments This work is supported by National Instrument Program (No.2012YQ030261) and National Natural Science Foundation of China (No. 51575441).
    Introduction The detection of pathogenic microorganisms via electrochemical methods is a promising approach because it offers the potential for fast, sensitive, user-friendly, and specific detection. Electrochemical impedance spectroscopy, specifically, is a versatile approach that has been successfully applied in the detection and quantification of a variety of biomolecules such as enzymes, antibodies, antigens, and DNA [1–3]; as well as for the detection of viruses, pathogenic bacteria, and eukaryotic Cytochrome Oxidase Activity Colorimetric Assay Kit [4–7]. Impedance-based detection methods rely upon the measurement of electrical impedance across an electrode that has been functionalized with a target-specific molecule, which is then exposed to a sample containing the target analyte. Here, the electrode acts as an electrical transducer that translates changes in electrical impedance at the analyte-electrode interface thus reflecting the presence or absence of the target. This signal can also be related to analyte concentration, thereby enabling quantification. Gold is a common electrode material because of its electrochemical properties, biocompatibility, and well-known surface chemistry, which allows controlled binding of biomolecules and other surface coatings [8–11]. The advantages of electrochemical impedance over existing methods include label-free detection, direct non-invasive, fast or real-time response, potential for miniaturization and integration into microfabricated systems, ease of use, and potential for low cost and mass production [5,12]. Low detection limits of a few colony-forming units (CFUs) have been reported using recently developed impedimetric immunosensors [5,13–15]. Although the best known and most widely applied pathogen detection systems are based on antigen-antibody interactions (i.e., immunosensors), other recognition elements such as aptamers are quickly gaining ground due to their high stability, comparable selectivity, and ease of synthesis, among other reasons [16]. These molecules are characterized by their smaller size and molecular weight relative to protein antibodies, and may require optimized experimental conditions for their successful application. In this regard, a suitable blocking agent may be required to prevent nonspecific binding, while not interfering with the capacity of the recognition element to interact with its target. In addition to limiting nonspecific binding, these materials may be employed simultaneously for multiple purposes such as spacers, as linkers with functional moieties, or to minimize nonspecific binding of the target molecule to the gold surface, thereby increasing its ability to interact with the target analyte [17,18]. The minimization of nonspecific binding to the gold electrode is critical because subsequent measurements depend on changes induced by total interactions between the electrode and the analyte. Furthermore, contaminants and other matrix components can contribute to the changes measured, thereby skewing the results.