Challenge for Trade-Off Relationship between the Mechanical Property and Healing Efficiency of Self-Healable Polyimide.

Polyimide is actively applied in various industrial fields because of its strong mechanical properties, owing to the interactions between the polymer chains. Fully aromatic imide structures exhibit high glass-transition temperatures due to the strong interactions between their chains, which hinder chain mobility. Therefore, preparing a material that exhibits self-healing at a low temperature of ≤100 °C and good mechanical properties is challenging. Thus, we prepared imides with four-component semiaromatic structures by adjusting the contents of 4,4'-(hexafluoroisopropylidene)diphthalic anhydride and 4,4'-(4,4'-isopropylidenediphenoxy)bis(phthalic anhydride) to yield four-component self-healable colorless polyimides (f-SH-CPIs) with novel structures, flexibilities, good mechanical properties, and low healing temperatures. The flexibilities and distances between the polymer chains, as the basis of the trade-off relationship between the mechanical properties and healing efficiency, were controlled. These materials may be used as substrates in wearable devices and multilayer insulation that may protect from space dust, cosmic rays, and satellite fragments.

Prediction of Stent Failure for Malignant Ureteral Obstruction in Non-Urological Cancer.

PURPOSE: To analyze prognostic factors associated with ureteral stent failure and to develop a prediction model for malignant ureteral obstruction (MUO) in patients with non-urological cancers. MATERIALS AND METHODS: We retrospectively reviewed patients with non-urological cancers who underwent ureteral stenting or percutaneous nephrostomy (PCN) for MUO between 2006 and 2014. Variables predicting stent failure were identified using Cox regression analysis. RESULTS: Of the 743 patients, 468 (63.0%) underwent ureteral stenting only, and 275 (37.0%) underwent PCN owing to technical (n=215) or functional (n=60) stent failure. The median overall survival was 4 [interquartile range (IQR) 1-11] months, and the median interval duration to stent failure was 2 (IQR 0-7) months. In univariate analysis, lower gastrointestinal cancer, previous radiotherapy to the pelvis, bladder invasion, lower ureteral obstruction, and low previous estimated glomerular filtration rate (eGFR) (<30 mL/min/1.73 m²) were significantly associated with a decreased survival rate. In multivariate analysis, bladder invasion and previous eGFR were significant predictors. With these two predictors, we divided patients into three groups based on their presence: low-risk (neither factor; n=516), intermediate-risk (one factor; n=206), and high-risk (both factors; n=21). The median stent failure-free survival rates of patients in the low-, intermediate-, and high-risk groups were 26 (8-unreached), 1 (0-18), and 0 (0-0) months, respectively (p<0.001). CONCLUSION: In cases of ureteral obstruction caused by non-urological cancers, patients with bladder invasion and a low eGFR showed poor stent failure-free survival. Therefore, PCN should be considered the primary procedure for these patients.

Two-dimensional material-based complementary ambipolar field-effect transistors with ohmic-like contacts.

Ambipolar field-effect transistors (FETs) possessing both electron and hole carriers enable implementation of novel reconfigurable transistors, artificial synaptic transistors, and output polarity controllable (OPC) amplifiers. Here, we fabricated a two-dimensional (2D) material-based complementary ambipolar FET and investigated its electrical characteristics. Properties of ohmic-like contacts at source/drain sides were verified from output characteristics and temperature-dependent measurements. The symmetry of electron and hole currents can be easily achieved by optimization of the MoS2or WSe2channels, different from the conventional ambipolar FET with fundamental issues related to Schottky barriers. In addition, we demonstrated successful operation of a complementary inverter and OPC amplifier, using the fabricated complementary ambipolar FET based on 2D materials.

Junctionless Electric-Double-Layer MoS2 Field-Effect Transistor with a Sub-5 nm Thick Electrostatically Highly Doped Channel.

Junctionless transistors are suitable for sub-3 nm applications because of their extremely simple structure and high electrical performance, which compensate for short-channel effects. Two-dimensional semiconductor transition-metal dichalcogenide materials, such as MoS2, may also resolve technical and fundamental issues for Si-based technology. Here, we present the first junctionless electric-double-layer field-effect transistor with an electrostatically highly doped 5 nm thick MoS2 channel. A double-gated MoS2 transistor with an ionic-liquid top gate and a conventional bottom gate demonstrated good transfer characteristics with a 104 on-off current ratio, a 70 mV dec-1 subthreshold swing at a 0 V bottom-gate bias, and drain-current versus top-gate-voltage characteristics were shifted left significantly with increasing bottom-gate bias due to an electrostatically increased overall charge carrier concentration in the MoS2 channel. When a bottom-gate bias of 80 V was applied, a shoulder and two clear peak features were identified in the transconductance and its derivative, respectively; this outcome is typical of Si-based junctionless transistors. Furthermore, the decrease in electron mobility induced by a transverse electric field was reduced with increasing bottom-gate bias. Numerical simulations and analytical models were used to support these findings, which clarify the operation of junctionless MoS2 transistors with an electrostatically highly doped channel.

Stable water-floating transistor with recyclability.

Electronic wastes from used devices containing environmentally hazardous materials are an immediate concern for the sustainable development of electronic and sensor industries. To address this, a highly controllable and dedicated electronic module should be devised, that allows systematic recollection of as many components from the original device for their reuse. Here, we report the total recycling of an electronic device, exploiting a water-floating system that is based on a water-compatible semiconductor as an active material. To do so, we developed a system for stable electronics on the water surface. The floating semiconductor features a tunable morphology on the water surface, and is constructed into a water-floating gated transistor (WFGT) and water floating sensor (WFS), exhibiting an on-current of 4.2 × 10-5 A and an on/off ratio of ∼103. The device showed high recyclability over 25 cycles, with an efficiency of 99 ± 0.9% within 1 cycle and 92 ± 0.7% within 30 cycles. Furthermore, the device was also found to be stable for over 10 days. Our system has the potential to be an eco-friendly, cost-effective, and scalable device that is fully recyclable, which can be applied in areas once thought of as being beyond the scope of current semiconductor technology.

Electrostatically Controllable Channel Thickness and Tunable Low-Frequency Noise Characteristics of Double-Gated Multilayer MoS2 Field-Effect Transistors with h-BN Dielectric.

Two-dimensional transition-metal dichalcogenide (TMD) materials have attracted increasing attention in efforts to overcome fundamental issues faced by the complementary metal-oxide-semiconductor industry. Multilayer TMD materials such as MoS2 can be used for high-performance transistor-based applications; the drive currents are high and the materials handle low-frequency (LF) noise well. We fabricated double-gated multilayer MoS2 transistors using the h-BN dielectric for the top gate and silicon dioxide for the bottom gate. We systemically investigated the bottom gate voltage (Vb)-controlled electrical characteristics and the top/bottom interface-coupling effects. The effective thickness of the MoS2 channel (tMoS2_eff) was well modulated by Vb, and tMoS2_eff reduction by negative Vb dramatically improved the Ion/Ioff ratio. Numerical simulation and analytical modeling with a variation of the depletion depth under different bias conditions verified the experimental results. We were also the first to observe Vb-tuned LF noise characteristics. Here, we discuss the Vb-affected series resistance and carrier mobility in detail. Our findings greatly enhance the understanding of how double-gated multilayer MoS2 transistors operate and will facilitate performance optimization in the real world.

Clinical Outcomes After Urinary Diversion for Malignant Ureteral Obstruction Secondary to Non-urologic Cancer: An Analysis of 778 Cases.

BACKGROUND: This study investigated patient outcomes after urinary diversion in order to manage malignant ureteral obstruction caused by non-urologic cancers and to evaluate predictive factors for overall survival. METHODS: The study retrospectively reviewed patients with non-urologic malignancies who underwent ureteral stenting or percutaneous nephrostomy for ureteral obstruction between 2006 and 2014. The variables for predicting overall survival were identified by Cox regression analysis. RESULTS: The study enrolled 778 patients, including 522 patients who underwent ureteral stenting and 256 patients who underwent percutaneous nephrostomy. Renal function was assessed immediately and then 2 weeks after urinary diversion. The median survival period was 5 months (interquartile range [IQR] 2-12 months). A total of 708 patients died. The patients who received chemotherapy after urinary diversion had a survival gain of 7 months compared with the patients who did not receive subsequent chemotherapy (p < 0.001). The survival rate did not differ between the various types of urinary diversion (p = 0.451). In the multivariate analysis, lower survival rates were significantly associated with male sex; previous chemotherapy without radiotherapy; an increasing number of events related to malignant dissemination; low preoperative hemoglobin (< 10 mg/dL), albumin (< 3 g/dL), and estimated glomerular filtration (< 60 mL/min/1.73 m2) rates; and no subsequent chemotherapy or radiotherapy. CONCLUSIONS: In cases of ureteral obstruction caused by non-urologic malignancies, the overall survival was poor. However, the patients who received chemotherapy after urinary diversion had a survival gain of 7 months. Therefore, urinary diversion could be considered to preserve renal function for subsequent chemotherapy, whereas patients with the poor prognostic factors should be presented with the option of no intervention.

Defect spectroscopy of sidewall interfaces in gate-all-around silicon nanosheet FET.

Through time-dependent defect spectroscopy and low-frequency noise measurements, we investigate and characterize the differences of carrier trapping processes occurred by different interfaces (top/sidewall) of the gate-all-around silicon nanosheet field-effect transistor (GAA SiNS FET). In a GAA SiNS FET fabricated by the top-down process, the traps at the sidewall interface significantly affect the device performance as the width decreases. Compare to expectations, as the width of the device decreases, the subthreshold swing (SS) increases from 120 to 230 mV/dec, resulting in less gate controllability. In narrow-width devices, the effect of traps located at the sidewall interface is significantly dominant, and the 1/f 2 noise, also known as generation-recombination (G-R) noise, is clearly appeared with an increased time constant (τ i ). In addition, the probability density distributions for the normalized current fluctuations (ΔI D) show only one Gaussian in wide-width devices, whereas they are separated into four Gaussians with increased in narrow-width devices. Therefore, fitting is performed through the carrier number fluctuation-correlated with mobility fluctuations model that separately considered the effects of sidewall. In narrow-width GAA SiNS FETs, consequently, the extracted interface trap densities (N T ) distribution becomes more dominant, and the scattering parameter ([Formula: see text]) distribution increases by more than double.

Channel Length-Dependent Operation of Ambipolar Schottky-Barrier Transistors on a Single Si Nanowire.

For use in flexible, printable, wearable electronics, Schottky-barrier field-effect transistors (SB-FETs) with various channel materials including low-dimensional nanomaterials have been considered so far due to their comparatively simple and cost-effective integration scheme free of junction and channel dopants. However, the electric conduction mechanism and the scaling properties underlying their performance differ significantly from those of conventional metal-oxide-semiconductor (MOS) field-effect transistors. Indeed, an understanding of channel length scaling and drain bias impact has not been elucidated sufficiently. Here, multiple ambipolar SB-FETs with different channel lengths have been fabricated on a single silicon nanowire ensuring a constant nanowire diameter. Their length scaling behavior is analyzed through drain current and transconductance contour maps, each depending on the drain and gate bias. The reduced gate control and extended drain field effect on Schottky junctions were observed in short channels. Activation energy measurements showed lower sensitive behavior of the Schottky barrier to gate bias in the short-channel device and confirmed the thinning of Schottky barrier width for electrons at the source interface with drain bias.

Effect of Potassium Ions on the Formation of Mixed-Valence Manganese Oxide/Graphene Nanocomposites.

One-pot synthesis of mixed-valence manganese oxide (MnOx)/potassium ion-doped reduced graphene oxide (rGO) composites for efficient electrochemical supercapacitors is introduced. Using manganese nitrate and potassium permanganate as co-precursors for the MnOx and by directly annealing the rGO without tedious purification steps, as described herein, MnOx/rGO composites with a high specific capacitance of 1955.6 F g-1 at a current density of 1 A g-1 are achieved. It is found that the presence of potassium ions helps in the development of mixed-valence MnOx on the surface of the rGO.

Web-drive based source measure unit for automated evaluations of ionic liquid-gated MoS2 transistors.

For reliable characterization of two-dimensional semiconducting devices and continuous monitoring in toxic environments, construction of an electrical characterization-based massive database using a portable source measure unit (SMU) with a WiFi connection is desirable. The web-drive based SMU using a microcontroller developed here exhibits superior voltage source performance (∼1 mV) and voltage/current measurement (∼0.15 mV/∼1 nA) capabilities, with automatic construction of a measurement database for online storage using web-drive based software, which can be applied for reliable electrical characterization. Electrical characterization of ionic liquid-gated MoS2 transistors was achieved with the designed SMU and showed results comparable with those obtained using a commercial semiconductor characterization system. Ionic liquid-gated transistors only require a small gate bias (∼1.5 V) for on-state operation because of the high gate capacitance originating from the thin dielectric layer constructed of an electrical double layer, which makes the device a promising candidate for low power consumption applications. Finally, several electrical parameters of the ionic liquid-gated transistor were extracted from the datasets and uploaded to the web-drive.

High-performance nanogap electrode-based impedimetric sensor for direct DNA assays.

The rapid and sensitive detection of pathogen DNA (Deoxyribonucleic acid) would be essential for diagnosis and appropriate antibiotic treatment time. Herein, we report a novel direct DNA detectable impedimetric sensor. Direct assay of the amplified target DNA (mecA gene from methicillin-resistant Staphylococcus aureus (MRSA)) was performed using the PCR (polymerase chain reaction) product without any purification. Even though there are lots of PCR reagents and excess salts in sample PCR product, the nanogap electrode-based impedimetric sensor was able to detect DNA amplification fast in 5th PCR cycle which had 260 fM mecA gene in sample originally. The 70 nm gap electrode sensor yielded over 20% signal increase at the 5th PCR cycle and the impedance change grew up to about 60% at 25th in case of sample with 260 fM mecA gene template originally. The increased concentration of target DNA template led to the rise in impedance change such as 60% up at 5th and 120% up at 25th cycle with 260 pM, respectively. It is very outstanding result as compared with the traditional PCR agarose gel. Besides, it is 7-fold superior sensitivity to the microgap electrode. Furthermore, genomic DNA sample extracted from MRSA was detected rapidly. The nanogap electrode-based impedimetric sensor could be a good candidate for a rapid, sensitive, and low-cost electrical biosensor for DNA characterization in diagnostics and disease monitoring.

Hybrid dielectrics composed of Al2O3 and phosphonic acid self-assembled monolayers for performance improvement in low voltage organic field effect transistors.

Low voltage operational organic transistors (< 4 V) based on pentacene were successfully fabricated with hybrid dielectric films composed of aluminum oxide using atomic layer deposition and various phosphonic acid-based self-assembled monolayers as the gate dielectrics. High capacitances up to 279 nF/cm2, low leakage current densities of 10-8 A/cm2 at 6 V, and high breakdown fields up to 7.5 MV/cm were obtained. The transistors with the octadecylphosphonic acid hybrid dielectric exhibited an improved saturation mobility of 0.58 cm2/Vs, a subthreshold slope of 151 mV/decade, a threshold voltage of - 1.84 V and an on-off current ratio of 106. The low surface energies of the self-assembled monolayers having non-polar terminal groups, such as methyl and pentafluorophenoxy, improved the carrier conduction of the transistors due to the pentacene growth with an edge-on orientation for low voltage operation. The pentafluorophenoxy end-group showed an accumulation of holes at the semiconductor-dielectric interface.

Scaling and Graphical Transport-Map Analysis of Ambipolar Schottky-Barrier Thin-Film Transistors Based on a Parallel Array of Si Nanowires.

Si nanowire (Si-NW) based thin-film transistors (TFTs) have been considered as a promising candidate for next-generation flexible and wearable electronics as well as sensor applications with high performance. Here, we have fabricated ambipolar Schottky-barrier (SB) TFTs consisting of a parallel array of Si-NWs and performed an in-depth study related to their electrical performance and operation mechanism through several electrical parameters extracted from the channel length scaling based method. Especially, the newly suggested current-voltage (I-V) contour map clearly elucidates the unique operation mechanism of the ambipolar SB-TFTs, governed by Schottky-junction between NiSi2 and Si-NW. Further, it reveals for the first-time in SB based FETs the important internal electrostatic coupling between the channel and externally applied voltages. This work provides helpful information for the realization of practical circuits with ambipolar SB-TFTs that can be transferred to different substrate technologies and applications.

Fabrication of a silica nanocable using hydroxyl-group core-engineered filamentous virus.

Biological materials with surface-active proteins can be genetically modified to bind target materials. In particular, filamentous-shaped M13 bacteriophages (M13 phage) are attractive scaffolds for functional nanostructures due to their highly ordered protein-coat surface. This paper demonstrates a simple method for fabricating silica nanocables along a modified M13 phage. The M13 phage was genetically engineered to display the amino acid serine on the surface to provide hydroxyl groups for a sol-gel reaction. This M13 phage mutant offers homogeneous molecular templates for forming silica coated coaxial nanocables. Silica shell formation was confirmed by transmission electron microscopy (TEM) and electron dispersive X-ray (EDX) analysis. The core-shell structures were clearly distinguishable in the TEM analysis, and the synthesized shells were observed by EDX analysis. In addition, we investigated the adsorption properties of M13 phages on the pretreated substrate as a function of concentration. The effect of the relative concentration of M13 phages on the substrate was observed by using atomic force microscopy (AFM). We also fabricated top electrodes on the extremely dense network for measuring electrical properties of the M13 phage. The experimental DC measurement indicated that the wild-type phage has very low electrical conductance, similar to insulating material.

The structural and electrical evolution of graphene by oxygen plasma-induced disorder.

Evolution of a single graphene layer with disorder generated by remote oxygen plasma irradiation is investigated using atomic force microscopy, Raman spectroscopy and electrical measurement. Gradual changes of surface morphology from planar graphene to isolated granular structure associated with a decrease of transconductance are accounted for by two-dimensional percolative conduction by disorder and the oxygen plasma-induced doping effect. The corresponding evolution of Raman spectra of graphene shows several peculiarities such as a sudden appearance of a saturated D peak followed by a linear decrease in its intensity, a relatively inert characteristic of a D' peak and a monotonic increase of a G peak position as the exposure time to oxygen plasma increases. These are discussed in terms of a disorder-induced change of Raman spectra in the graphite system.