The effects of a recessed gate structure on the device performance of sol-gel-based metal-oxide thin-film transistors (oxide-TFTs) consisting of aluminum oxide dielectric and indium-gallium-zinc ...oxide semiconducting films fabricated through effective microwave irradiation are investigated, as compared with elevated and non-patterned gate structures. Low-voltage operating oxide-TFTs with an optimized recessed gate structure exhibited improved device performance including OFF-state current of approximately 10<inline-formula> <tex-math notation="LaTeX">^{-\text{11}}</tex-math> </inline-formula> A and field-effect mobility of 3.4 cm<inline-formula> <tex-math notation="LaTeX">^{\text{2}}</tex-math> </inline-formula>/V-s in the linear regime, compared with those with elevated (<inline-formula> <tex-math notation="LaTeX">\sim</tex-math> </inline-formula>10<inline-formula> <tex-math notation="LaTeX">^{-\text{9}}</tex-math> </inline-formula> A and 1.9 cm<inline-formula> <tex-math notation="LaTeX">^{\text{2}}</tex-math> </inline-formula>/V-s) and non-patterned (<inline-formula> <tex-math notation="LaTeX">\sim</tex-math> </inline-formula>10<inline-formula> <tex-math notation="LaTeX">^{-\text{10}}</tex-math> </inline-formula> A and 2.8 cm<inline-formula> <tex-math notation="LaTeX">^{\text{2}}</tex-math> </inline-formula>/V-s) gate structures. Furthermore, the charge transport mechanism responsible for improved device performance and operational stability against prolonged positive and negative gate bias stresses in the oxide-TFTs with the recessed gate structure is investigated through activation energy and velocity distribution that are determined from direct-current and time-domain non-quasi-static transient analyses, respectively. Finally, enhancement-load-type nMOS inverters operating at 5 V are developed for logic circuits, which exhibit a relatively high dc gain of 32.2 in the recessed gate structure, compared with that of 17.1 and 27.1 in the elevated and the non-patterned gate structures, respectively.
The use of the charge-screening method to obtain high-performance solution-processed zinc-tin-oxide (ZTO) thin-film transistors (TFTs) for transparent flexible displays is investigated. The proposed ...ZTO TFTs employing solution-processed ferroelectric, poly (vinylidenefluoride-co- trifluoroethylene) (PVDF-TrFE) copolymer exhibit excellent switching characteristics, including a shift in the threshold voltage toward 0 V and a decrease in the OFF-state current and the sub-threshold swing. The long-term stability of ZTO/PVDF-TrFE TFTs against electrical bias combined with visible-light illumination at 60 °C is also demonstrated. The proposed method is based on an all-solution-process that was carried out below 100°C except the metal deposition, and this allows the ZTO TFT matrix to be integrated into transparent display backplanes on flexible substrates.
Microwave-assisted functionalization of zinc oxide nanoflowers (ZnO NFs) with palladium nanoparticles (Pd NPs) is demonstrated to realize high-performance chemiresistive-type hydrogen (H2) gas ...sensors operating at room temperature (RT). The developed gas sensors exhibit a high response of up to 70% at 50 ppm and a theoretical detection limit of 10 ppb. The formation of ZnO NFs with an enhanced specific surface area and their functionalization with Pd NPs are investigated through various characterizations. Furthermore, the optimization of microwave absorption upon the structural incorporations between nanostructures (NF–NPs) is investigated for solution-based functionalization at low temperatures (below 120 °C) for short process times (within 1 min), compared to the conventional thermal annealing at 250 °C for 1 h. Highly sensitive and selective ZnO-based gas sensors enabling the detection of H2 gas molecules at 300 ppb concentration at RT exhibit a short response/recovery time of below 3 min and a good selectivity toward different gases including nitric oxide, carbon monoxide, and oxygen. The successful functionalization of nanostructured metal oxide semiconductors (MOSs) with metal NPs via effective and practical microwave absorption enhances the potential on highly sensitive and selective chemiresistive-type MOS-based gas sensors operating at RT without additional heaters or photogenerators.
Wearable chemical sensors can provide crucial human-physiology information by monitoring humidity in various environments. Capacitive-type humidity sensors based on poly(ionic liquid) (PIL) as the ...sensing material, which was synthesized via the polymerization of an ionic liquid (IL) were developed. The PIL films fabricated through a facile bar-printing process in ambient air, exhibited outstanding capacitive characteristics over a broad relative humidity (RH) range of 10%−80% at frequencies between 100 Hz and 1 MHz. Notably, high sensitivity (1.8 nF/%RH), good linearity (R2 = 0.980), low hysteresis, and fast response (~20 ms) of the developed humidity sensors were achieved. The corresponding sensing mechanism of the PIL for capacitive-type humidity sensors was studied by investigating the chemisorption of water molecules on the PIL surface and proton hopping through multiple layers of water molecules physisorbed on chemisorbed water molecules through single hydrogen bonding. In addition, the operational stability of the wearable humidity sensors developed in this study was investigated by analyzing the capacitive characteristics of the PIL sensing material at various temperatures (20–60 °C), even under a bending state and after 20,000 bending-stress cycles with a strain of 30%. Finally, a real-time humidity monitoring system integrated with signal processing and wireless communication modules was demonstrated by analyzing real-time capacitive signals acquired from a wearable humidity sensor attached to a human wrist and by visualizing processed humidity information on a user’s smartphone.
Display omitted
•Wearable humidity sensors consisting of polymerized ionic liquid fabricated by bar-printing were developed.•High sensitivity, good linearity, low hysteresis, and fast response of the proposed sensors were achieved•A real-time humidity monitoring system integrated with a user’s smartphone was demonstrated.
Identification of pleiotropic variants associated with multiple phenotypic traits has received increasing attention in genetic association studies. Overlapping genetic associations from multiple ...traits help to detect weak genetic associations missed by single-trait analyses. Many statistical methods were developed to identify pleiotropic variants with most of them being limited to quantitative traits when pleiotropic effects on both quantitative and qualitative traits have been observed. This is a statistically challenging problem because there does not exist an appropriate multivariate distribution to model both quantitative and qualitative data together. Alternatively, meta-analysis methods can be applied, which basically integrate summary statistics of individual variants associated with either a quantitative or a qualitative trait without accounting for correlations among genetic variants. We propose a new statistical selection method based on a unified selection score quantifying how a genetic variant, i.e., a pleiotropic variant associates with both quantitative and qualitative traits. In our extensive simulation studies where various types of pleiotropic effects on both quantitative and qualitative traits were considered, we demonstrated that the proposed method outperforms the existing meta-analysis methods in terms of true positive selection. We also applied the proposed method to a peanut dataset with 6 quantitative and 2 qualitative traits, and a cowpea dataset with 2 quantitative and 6 qualitative traits. We were able to detect some potentially pleiotropic variants missed by the existing methods in both analyses. The proposed method is able to locate pleiotropic variants associated with both quantitative and qualitative traits. It has been implemented into an R package 'UNISS', which can be downloaded from http://github.com/statpng/uniss.
We demonstrate high-performance wearable electronic-bandage (E-bandage) based on carbon nanotube (CNT)/silver nanoparticle (AgNP) composites covered with flexible media of fluoropolymer-coated ...polydimethylsiloxane (PDMS) films. The E-bandage can be used for motion-related sensors by directly attaching them to human skin, which achieves a fast and accurate electric response with high sensitivity according to the bending and stretching movements that induce changes in the conductivity. This advance in the E-bandage is realized as a result of the sensitivity that can be achieved by controlling the concentration of AgNPs in CNT pastes and by modifying the device architecture. The fluoropolymer encapsulation with hydrophobic surface characteristics allows for the E-bandage to operate in water and protects it from physical and chemical contact with the daily life conditions of the human skin. The reliability and scalability of the E-bandage as well as the compatibility with conventional microfabrication allow new possibilities to integrate flexible human-interactive nanoelectronics into mobile health-care monitoring systems combined with Internet of things (IoTs).
Display omitted
•Flexible chemiresistive pH sensors based on printed nanocomposites of SWCNTs and Nafion are demonstrated.•The operational stability of flexible pH sensors is investigated by ...performing bending tests.•A real-time pH sensor system integrated into a drone application for monitoring water quality is demonstrated.
High-performance flexible pH sensors based on nanocomposites of single-wall carbon nanotubes (SWCNTs) and Nafion, fabricated by screen printing on flexible substrates in ambient air are demonstrated. The electrical characteristics and thus the sensing performance of the pH sensors monitoring the change in resistance of printed nanocomposite films in a wide range of pH from 1 to 12 were controlled by the number of printed layers in multi-patterns. The operational stability of the flexible pH sensors was nearly unchanged after 200 cycles of bending tests having a curvature radius of 5 mm, which is essential for intergration of flexible pH sensors into wearable nanoelectronics. The sensing mechanism of the chemiresistive pH sensors based on nanocomposites is investigated in terms of chemical reaction. The hydrogen or hydroxide ions in the pH solution interact with the carbonyl and CH bonds bonds of the nanocomposite film, which induces or withdraws positively charged carriers, respectively. In addition, a real-time pH sensor system integrated into a drone application with wireless communication and data transmitting modules is demonstrated for the simultaneous visualization of processed data and remote detection of targets on the user's smartphone based on a designed Android algorithm.
Display omitted
•We demonstrate highly sensitive wearable SWCNT-based glucose sensor systems upon smartphone.•Surface-functionalization with GOD-nafion composites enhanced the sensing performance of ...glucose sensors.•We investigate the sensing mechanism of glucose sensors by analyzing the oxidation-reduction reaction.•Wearable glucose sensors fabricated by all-solution process can open up a new route for health-care diagnosis system.
Since the first demonstration of a biosensor was reported, big efforts have been reported to improve the sensing performance of bioelectronics by investigating the material compositions, device configurations, process optimization, and system integration. In this paper, we demonstrate highly sensitive wearable carbon-based glucose sensors fabricated by all-solution process at low temperature. Solution-processed single-wall carbon nanotube (SWCNT) random networks as a sensing platform were surface-functionalized with the enzyme glucose oxidase (GOD)-nafion composites, which can detect glucose down to 50 μM with a response time of less than 5 s. We also investigate the sensing mechanism of SWCNT-based glucose sensors through molecular oxidation-reduction reactions in GOD with glucose. Material characterization using X-ray photoelectron spectroscopy and Raman spectra measurements proves the existence of SWCNT random networks with chemical incorporation through a surface-functionalization process. We believe that the proposed wearable SWCNT-based glucose sensors fabricated by all-solution process can open up a promising route to realize a low-cost and high performance health-care diagnosis system integrated with the user’s smartphone for diabetic patients.
PDF
