In this work, a disposable paper-plastic hybrid microfluidic lab-on-a-chip (LOC) has been developed and successfully applied for the colorimetric measurement of urine by the smartphone-based optical platform using a "UrineAnalysis" Android app. The developed device was cost-effectively implemented as a stand-alone hybrid LOC by incorporating the paper-based conventional reagent test strip inside the plastic-based LOC microchannel. The LOC device quantitatively investigated the small volume (40 μL) of urine analytes for the colorimetric reaction of glucose, protein, pH, and red blood cell (RBC) in integration with the finger-actuating micropump. On the basis of our experiments, the conventional urine strip showed large deviation as the reaction time goes by, because dipping the strip sensor in a bottle of urine could not control the reaction volume. By integrating the strip sensor in the LOC device for urine analysis, our device significantly improves the time-dependent inconstancy of the conventional dipstick-based urine strip, and the smartphone app used for image analysis enhances the visual assessment of the test strip, which is a major user concern for the colorimetric analysis in point-of-care (POC) applications. As a result, the user-friendly LOC, which is successfully implemented in a disposable format with the smartphone-based optical platform, may be applicable as an effective tool for rapid and qualitative POC urinalysis.

In this paper, a biomimetic cilia‐patterned flexible electrode using ultra conductive polydimethylsiloxane (PDMS) is presented. Due to the flexibility and cilia patterns, the developed electrode can have conformal contact with the human skin without interruptions of hair and rough skin. The conductive PDMS is prepared by mixing PDMS prepolymer and curing agent with Ag particles at different ratios. The performance of the best composite‐made ciliated electrode is evaluated under different skin‐like physical environments, and compared to the nonciliated flat electrode. For a typical flat electrode, hair and rough surface of the human skin disturb electrical contact, increasing contact impedance, whereas flexible ciliary structures of the proposed electrode show significantly improved conductivity passing through the furs to penetrate well into the gap on the alloyed skin, thus increasing the contact areas. Furthermore, bio‐signal measurement using rigid metal electrodes suffers from motion artifacts causing signal errors due to bodily movement, which is remarkably addressed by ciliated flexible electrode. Therefore, the proposed electrode is applied to recording electrocardiography signal and compared with signal measured with conventional metal electrode, which showed about 20% enhancement than that of metal counterpart in identifying electrical activity of heart muscle of a person, as point‐of‐care clinical applications.

In this work, a low-cost PDMS micro-pump and -valve have been designed and developed to control multiple reagents for enzyme-linked immunosorbent assay (ELISA) on a programmable lab-on-a-chip (LOC) platform. The micro pump and valves were precisely controlled by selectively pressurizing the PDMS channels and chamber to actuate the multiple reagents in a controlled manner. Selective pressurizing of the PDMS structures was initiated by a simple system that maneuvered a single roller bar operated by a programmed microprocessor. The performance of the micro-pump was fully characterized and a minimum fluid volume of 1 μL was controlled. Also, the on-chip microvalves were programmed to flow the multiple reagents to automatically process the multi-step ELISA procedures. By applying the proposed platform, 19.40 pg ml-1 cardiac troponin T (cTnT) was successfully detected on the LOC device by using multiple programmed valves as multiple steps of the enzyme-linked sandwich immunoassay. As a result, the developed micro-pump and -valve, which were successfully applied to actuate a series of solutions in a controlled manner, can be widely applied to lab-on-a-chip based bioassays.

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