Precursor solutions and a solution process were developed for the fabrication of amorphous oxide thin-film transistors (TFTs). All the layers of the TFTs comprised oxide films prepared from precursor solutions. The gate lines, gate insulator, and channel layer comprised ruthenium oxide, lanthanum zirconium oxide, and zirconium indium zinc oxide films. The polysilazane-based silicon dioxide film was used for the channel stopper layer. The source-line and drain electrode had a double-layer structure comprising indium tin oxide and ruthenium oxide films. The silsesquioxane-based silicon dioxide and ruthenium oxide films were used for the passivation layer and pixel electrodes, respectively. The TFTs exhibited a field effect mobility of 2.68 cm 2 V À1 s À1 , a sub-threshold swing of 1.09 V/decade, a threshold voltage of 3.06 V, and an on/off ratio of 10 5 . Active-matrix electrophoretic displays (EPDs) with a resolution of 101.6 ppi were successfully fabricated using the all-solution-processed TFTs. Bi-stable black/ white images were confirmed in these TFT-EPDs for the first time.
Microfluidic paper-based analytical devices (μPADs) are promising biosensors that may be used in a variety of bioanalytical applications. A μPAD for automating the competitive enzyme-linked immunosorbent assay (ELISA) of small-sized target detection at the femtogram level using submicroliter samples is reported in this study. The proposed μPAD was integrated with a sucrose valve to automate the sequential delivery of reagents, providing simple control of reagent delivery time and simple operation. The use of a sample solution dropping location at the zones on the device that had been prepared with an antibody-conjugated enzyme before immersion in a running buffer allowed minimization of sample volume to 0.6 μL, while eliminating the possible loss of a target molecule by adsorption on the membrane, thus improving detection sensitivity. Furthermore, the proposed device was successfully applied to the automation of competitive ELISA for the detection of aflatoxin B 1 (AFB 1 ), a potent carcinogen that causes substantial health risks to humans worldwide, with a detection limit of 60 femtograms or 0.1 ng/mL. The method developed in this study provides high sensitivity, small sample volume, on-site and equipment-free measurements, low-cost operation, and user-friendliness. This approach could be used to analyze small-sized molecules in the fields of food safety and quality control, environmental monitoring, and clinical diagnostics.
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