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The tapered channel effect is a major concern in three-dimensional (3-D) NAND technology because the effect causes differences in the electrical characteristics, including the threshold voltage (VT), between the upper and the lower cells. We simulated the tapered channel effect by using Sentaurus technology, computer-aided design (TCAD) tools, and based on the results, we propose a novel method to lessen the non-uniformity of the threshold voltage shift ( ${\Delta }\text{V}_{\mathrm{ T}}$ ) between the cells. The difference in ${\Delta }\text{V}_{\mathrm{ T}}$ between the upper and the lower cells due to the tapered channel can be reduced by employing a tapered blocking oxide layer with a proper taper angle. These results will be helpful in designing reliable 3-D NAND flash memories.

Tungsten disulfide (WS2) quantum dots (QDs) embedded in polyvinylpyrrolidone (PVP) based flexible memristive devices were prepared, and those devices exhibited typical bistable electrical switching and remarkable nonvolatile memristive behaviors. Maximum electricity ON/OFF ratio obtained from the current–voltage (I-V) curves of the device is close to 104. The set voltage of the device is +0.7 V, which effectively reduced the energy consumption. The retention times extracted from data for the devices were as large as 1 × 104 s, which points to these devices having nonvolatile characteristics. Moreover, the highly flexible characteristics of the devices were demonstrated by bending the devices. The carrier transport mechanisms were explained by fitting the I-V curves, and possible operating mechanisms of the devices can be described based on the electron trapping and detrapping processes. WS2 QDs uniformly dispersed in pure transparent N, N-Dimethylformamide (DMF) were obtained by using ultrasonication and a hydrothermal process in this work.

The motion blur of a large-size, organic, light-emitting device (OLED) panel could be reduced by decreasing the moving-picture response time (MPRT). The MPRT of an OLED display panel with a fast response was significantly affected by the frame frequency and the compensation driving method, and the MPRTs of large-size OLED display panels could be significantly decreased by using an integrated gate driver circuit with a MPRT reduction method. The MPRT was decreased due to the ability to turn the emitting pixels off in advance, which was possible due to the provision of black data. The integrated gate drivers were designed so that a normal display, black data insertion, and operation in the compensation mode could be achieved. The MPRT of a 65-inch ultra-high-definition (UHD) OLED panel was decreased to 3.4 ms by using an integrated gate driver circuit. The MPRT reduction method proposed in this study can reduce the MPRT time to below 6.8 ms according to the black data insertion duty. This MPRT time of 6.8 ms can be further reduced to 3.4 ms in 50% black data duty, showing a 50% MPRT improvement. Thus, the motion blur of such large-size OLED display panels can be significantly reduced by decreasing the value of the MPRT.

This paper reports data for the electrical characteristics and the operating mechanisms of flexible resistive switching devices based on WS2 nanosheets (NSs) dispersed in a poly(methyl methacrylate) (PMMA) layer. The ON/OFF ratio of the memristive device based on an Al/WS2 NSs:PMMA/indium tin oxides (ITO) structure was approximately 5.9 × 104. The memristive device based on the WS2 NSs also exhibited the bipolar switching characteristics with low power consumption and great performance in the bent state with radii of the curvatures of 20 and 10 mm. Especially, the results obtained after bending the device were similar to those observed before bending. The device showed nearly the same ON/OFF ratio for a retention time of 1 × 104 sec, and the number of endurance cycles was greater than 1 × 102. The set voltage and the reset voltage probability distributions for the setting and the resetting processes indicated bipolar switching characteristics. The operating and the carrier transport mechanisms of the Al/WS2 NSs:PMMA/ITO device could be explained based on the current-voltage results with the aid of an energy band diagram.

The central nervous system sends a neural impulse through an efferent nerve system toward muscles to drive movement. In an electronically artificial neural system, the electronic neural devices and interconnections prevent achieving highly connected and long-distance artificial impulse transmission and exhibit a narrow bandwidth. Here we design and demonstrate light-emitting memristors (LEMs) for the realization of an optoelectronic artificial efferent nerve, in which the LEM combines the functions of a light receiver, a light emitter, and an optoelectronic synapse in a single device. The optical signal from the pre-LEM (presynaptic membrane) acts as the input signal for the post-LEM (postsynaptic membrane), leading to one-to-many transmission, dynamic adjustable transmission, and light-trained synaptic plasticity, thus removing the physical limitation in artificially electronic neural systems. Furthermore, we construct an optoelectronic artificial efferent nerve with LEMs to control manipulators intelligently. These results promote the construction of an artificial optoelectronic nerve for further development of sensorimotor functionalities.

Fabrication of human-like intelligent tactile sensors is an intriguing challenge for developing human-machine interfaces. As inspired by somatosensory signal generation and neuroplasticity-based signal processing, intelligent neuromorphic tactile sensors with learning and memory based on the principle of a triboelectric nanogenerator are demonstrated. The tactile sensors can actively produce signals with various amplitudes on the basis of the history of pressure stimulations because of their capacity to mimic neuromorphic functions of synaptic potentiation and memory. The time over which these tactile sensors can retain the memorized information is alterable, enabling cascaded devices to have a multilevel forgetting process and to memorize a rich amount of information. Furthermore, smart fingers by using the tactile sensors are constructed to record a rich amount of information related to the fingers' current actions and previous actions. This intelligent active tactile sensor can be used as a functional element for artificial intelligence.

The effect of a modified cell structure in the gate region on the electrical characteristics of three-dimensional (3D) NAND flash memory devices was investigated by using a technology computeraided design simulation. The interference in the memory devices induced by the pass voltage (Vpass) interference of 3D NAND flash was significantly affected depending on the cell size. The Vpass memory device with a modified cell structure was reduced due to an increase in the electron density of the inversion layer in comparison with conventional 3D flash memory devices, and their program operation was enhanced by the increased electric field. Furthermore, the program/erase margin of the proposed 3D NAND flash memory device was 15% larger than that of the conventional 3D NAND flash memory device.

In this letter, we demonstrate the fabrication of flexible memristive devices using tungsten di-selenide (WSe2) quantum dots (QDs) as the active layer. The WSe2 QDs were synthesized by facile two-step technique consisting of solvothermal and sonication processes to utilize the charge-trapping sites in the memristive devices. The sizes of as-synthesized WSe2 QDs, as determined from the transmission electron microscopy image, were in the range between 3 and 5 nm. Current–voltage ( ${I}-{V}$ ) curves for the flexible memristive devices based on nanocomposites consisting of WSe2 QDs sandwiched between two poly (methyl methacrylate) (PMMA) layers showed remarkable bi-stable behavior before and after bending. The ON/OFF ratio of the memory devices before and after bending were approximately $1\times 10^{{2}}$ and $1\times 10^{{2}}$ , respectively. The devices showed the nonvolatile memory effect with a retention time of more than $7\times 10^{{2}}\text{s}$ . The endurance number of ON/OFF switching cycles for the devices was $1\times 10^{{2}}$ . The bipolar resistive switching behavior was described on the basis of the ${I}-{V}$ results by analyzing the effect of space charge.

Healthy and uncomplicated lupus pregnancies exhibit early and sustained transcriptional modulation of lupus-related pathways. This might contribute to fetal tolerance while predisposing pregnant women to certain infections. Failure to modulate these pathways is associated with lupus pregnancy complications., Systemic lupus erythematosus carries an increased risk of pregnancy complications, including preeclampsia and fetal adverse outcomes. To identify the underlying molecular mechanisms, we longitudinally profiled the blood transcriptome of 92 lupus patients and 43 healthy women during pregnancy and postpartum and performed multicolor flow cytometry in a subset of them. We also profiled 25 healthy women undergoing assisted reproductive technology to monitor transcriptional changes around embryo implantation. Sustained down-regulation of multiple immune signatures, including interferon and plasma cells, was observed during healthy pregnancy. These changes appeared early after embryo implantation and were mirrored in uncomplicated lupus pregnancies. Patients with preeclampsia displayed early up-regulation of neutrophil signatures that correlated with expansion of immature neutrophils. Lupus pregnancies with fetal complications carried the highest interferon and plasma cell signatures as well as activated CD4+ T cell counts. Thus, blood immunomonitoring reveals that both healthy and uncomplicated lupus pregnancies exhibit early and sustained transcriptional modulation of lupus-related signatures, and a lack thereof associates with adverse outcomes., Graphical Abstract

An electronic synapse (e-synapse) based on memristive switching is a promising electronic element that emulates a biological synapse to realize neuromorphic computing. However, the complex resistive switching process it relies on hampers the reproducibility of its performance. Thus, achievement of a reproducible electronic synapse with a high rate of finished products has become a significant challenge in the development of an artificial intelligent circuit. Here, we demonstrate an ultrathin e-synapse having high yield (>95%), minimal performance variation, and extremely low power consumption based on an Al2O3/graphene quantum dots/Al2O3 sandwich structure that was fabricated using atomic layer deposition. The e-synapse showed both high device-to-device and cycle-to-cycle reproducibility with high stability, endurance, and switching uniformity, because the essential synaptic behaviors could be observed. This implementation of an e-synapse with an Al2O3/graphene quantum dots/Al2O3 structure should intensify motivation for engineering e-synapses for neuromorphic computing. Circuits that emulate the actions of biological synapses can be fabricated from devices known as quantum tunnel junctions. Fushan Li from China’s Fuzhou University, Tae Whan Kim from Korea’s Hanyang University, and colleagues produced an ‘e-synapse’ where a thin insulating film prevents electrons from moving through a circuit, except for a small number that jump across the barrier through quantum tunneling. When the researchers embedded graphene quantum dots in the film, they found that these nanoparticles switched the device between low and high resistance states by either trapping or releasing tunneling electrons. This allows the circuit to mimic certain functions of the brain; the gradual accumulation of electrons and their spontaneous release, for example, occurred on timeframes similar as seen in short-term memory loss. The team’s manufacturing scheme yielded devices with high stability and reproducibility. This article demonstrates an ultrathin e-synapse having high yield, minimal performance variation, and extremely low power consumption based on a Al2O3/graphene quantum dots/Al2O3 sandwich structure that was fabricated by using atomic layer deposition. It showed both high device-to-device and cycle-to-cycle reproducibility with high stability, endurance, and switching uniformity, because of which the essential synaptic behaviors could be observed. This implementation of an e-synapse with an Al2O3/graphene quantum dots/Al2O3 structure should intensify motivation for engineering e-synapses for neuromorphic computing.

Harvesting walking energy to generate sustainable power is critical for the development of portable and wearable electronics. Here, we demonstrate that by ingeniously taking advantage of natural triboelectrification and static charges on the human body, electric energy can be generated from our walking without the use of a specially designed shoe/sole or triboelectric nanogenerator (TENG). The triboelectric system is composed of only Al electrodes, which makes it compatible with wearables due to its lightweight and flexibility. The electricity generated from every step during walking is sufficient to light up 100 commercial light-emitting diodes (LEDs) instantaneously. Furthermore, the simple system can act as a self-powered active sensor for monitoring our gait during walking, our health, and security. The triboelectric system is ultra-simple, lightweight, eco-friendly, and low-cost, which gives it potential for application in attachable electronics as a sustainable power source and a self-powered sensor.

Large-size, organic light-emitting device (OLED) panels based on highly reliable gate driver circuits integrated using InGaZnO thin-film transistors (TFTs) were fabricated to achieve ultra-high image density (UHD). These large-size OLED panels were driven by using a novel gate driver circuit not only for displaying images but also for sensing TFT characteristics for external compensation. Regardless of the negative threshold voltage of the TFTs, the proposed gate driver circuit in OLED panels functioned precisely, resulting from a decrease in the leakage current. The falling time of the circuit is approximately $1.6~{{\mu }}\text{s}$ , which is fast enough to drive UHD OLED displays at 120 Hz. 120 Hz is most commonly used as the operating voltage because images consisting of 12 frames per second can be quickly shown on the display panel without any image sticking. The reliability tests showed that the lifetime of the proposed integrated gate driver is at least $1 \times 10^{5}$ h.

The variations in the threshold voltage and the mobility of In–Ga–Zn–O thin-film transistors (TFTs) were significantly compensated by the proposed compensation method. The luminance difference at each pixel in the large-size organic light-emitting devices (OLEDs) was dramatically decreased less than 10% due to the stich mural and the applied data voltage difference at low gray scale level. Luminance uniformities of up to 99% were achieved for all gray levels of the OLEDs by using the external circuit and optical compensation with angle calibration.

This paper reports a facile, cost effective method that uses an aqueous hydrothermal process for synthesizing two-dimensional molybdenum disulphide (MoS2) monolayer quantum dots (QDs) and their potential applications in flexible memristive devices. High-resolution transmission electron microscopy and atomic force microscopy images confirmed that the diameters of the synthesized MoS2 QDs with irregular shapes were in the range between 3 and 6 nm; their thicknesses were confirmed to lie between 1.0 and 0.8 nm, a clear indication that a monolayer of MoS2 QDs had been synthesized. Photoluminescence (PL) and time-resolved PL spectra of the MoS2 QDs revealed a strong emission in the blue region with a slower decay constant. Memristive devices fabricated by incorporating MoS2 QDs between poly(methylsilsesquioxane) ultrathin layers, which had been deposited on poly(ethylene terephthalate), demonstrated a high ON–OFF current ratio of ∼104, stable retention, and excellent endurance in the relaxed state; these devices were also demonstrated to function properly during bending and in a bent state. The flexible memristive devices demonstrated an OFF state with a very low current of 10−6 A. These results clearly show that ultrathin two-dimensional QDs have promising applications in high-performance flexible memristive devices.

Biosynaptic devices based on chicken egg albumen (CEA):graphene quantum dot (GQD) hybrid nanocomposites were fabricated to achieve stable synaptic behaviors. Current-voltage (I-V) curves for the biosynaptic devices under consecutive negative and positive voltage sweeps showed clockwise pinched hysteresis, which is a critical feature of a biological synapse. The effect of the GQD concentration in the CEA layer on the device performance was studied. The retention time of the biosynaptic devices was relatively constant, maintaining a value above 104 s under ambient conditions. The carrier transport mechanisms of the biosynaptic devices were described and analyzed on the basis of the slopes of the I-V curves and their fittings.

Perovskite materials have been utilized as promising active materials for memristive devices due to their excellent properties. However, most reported perovskite-based memristive devices exhibit relatively low current ON/OFF ratios, which limits their practical applications in memory devices. In this work, memristive devices with a large memory margin were fabricated utilizing a CH3NH3PbBr3 (MAPbBr3) perovskite layer. The nanocrystalline MAPbBr3 perovskite thin films were successfully formed at low temperature by using a chlorobenzene dripping method. The MAPbBr3 perovskite layer was employed as a resistive switching layer in memristive devices with a structure of indium-tin-oxide/poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate)/MAPbBr3/Al. The maximum ON/OFF ratio of the memristive devices based on the MAPbBr3 perovskite was as large as 3.6ｘ106. The memristive devices showed high device-to-device reproducibility with set-voltage distributions between −0.5 and −0.8 V, as well as good endurances of at least 120 cycles and retention times longer than 1ｘ104 s. The carrier transport mechanisms of the memristive devices were described on the basis of the I-V curves, and their operating mechanisms were explained via the formation and rupture of filaments in the MAPbBr3 perovskite.

The development of portable power banks by using triboelectric nanogenerator-based technology has been a subject of great interest. However, when the potential wide range of future applications of such devices is considered, their heavy use of nanomaterials, polymers, and micro/nano fabrication technologies will increase the cost of and the energy consumed during production; moreover, their improper disposal may harm the environment. Here, we demonstrate portable card-type triboelectric nanogenerators (Card-TENGs) assembled by using less problematic, readily available materials through a top-down approach. The Card-TENGs are fabricated mainly from paper, including card paper and printer paper, which can greatly reduce the fabrication cost and the risk to the environment. Electricity can be generated simply by shaking the Card-TENGs, and Card-TENGs can be combined to form single and multilayer structures, which will enhance their electrical output. Furthermore, the as-fabricated Card-TENGs can be easily integrated into packs to increase the total output for lighting LEDs arrays and powering calculators.

One diode and one resistor (1D–1R) memristive devices based on inorganic Schottky diodes and poly(methylsilsesquioxane) (PMSSQ):graphene quantum dot (GQD) hybrid nanocomposites were fabricated to achieve stable memory characteristics. Current-voltage (I-V) curves for the Al/PMSSQ:GQDs/Al/p-Si/Al devices at room temperature exhibited write-once, read-many-times memory (WORM) characteristics with an ON/OFF ratio of as large as 104 resulting from the formation of a 1D–1R structure. I-V characteristics of the WORM 1D–1R device demonstrated that the memory and the diode behaviors of the 1D–1R device functioned simultaneously. The retention time of the WORM 1D–1R devices could be maintained at a value larger than 104 s under ambient conditions. The operating mechanisms of the devices were analyzed on the basis of the I–V results and with the aid of the energy band diagram.

Flexible memristive devices with a structure of Al/polyimide:mica/poly(3,4-ethylenedioxythiophene) polystyrene sulfonate/indium-tin-oxide/polyethylene glycol naphthalate showed electrical bistability characteristics. The maximum current margin of the devices with mica nanosheets was much larger than that of the devices without mica nanosheets. For these devices, the current vs. time curves showed nonvolatile characteristics with a retention time of more than 1 × 104 s, and the current vs. number-of-cycles curves demonstrated an endurance for high resistance state/low resistance state switchings of 1 × 102 cycles. As to the operation performance, the “reset” voltage was distributed between 2.5 and 3 V, and the “set” voltage was distributed between −0.7 and −0.5 V, indicative of high uniformity. The electrical characteristics of the devices after full bendings with various radii of curvature were similar to those before bending, which was indicative of devices having ultra-flexibility. The carrier transport and the operation mechanisms of the devices were explained based on the current vs. voltage curves and the energy band diagrams.

OBJECTIVES The purpose of this study was to examine the differences of wearing shoes and barefoot on lower limb muscle functions in martial arts athletes of university. METHODS Fourteen martial arts athletes participated in this study. Lower limb muscle functions (maximum strength, power, and electromyography) and balance were measured when wearing shoes (WS) and barefoot (BF). Measured data were analyzed using IBM SPSS Statistics ver. 23.0 (IBM Co., Armonk, NY, USA). Paired t-test was used for comparison between WS and BF. RESULTS Maximum muscle strength (absolute and relative squat 1RM) and static balance (Standing on one leg with eyes close) were significantly higher in BF compared to WS. Although maximum muscle power and dynamic balance were higher in BF compared to WS, were non-significant. Muscle activities of rectus femoris and vastus lateralis were higher during WS than BF. CONCLUSIONS The results of this study suggest that Application of barefoot training seems to be effective on expression of lower limb maximum muscle strength and static balance in martial arts athletes of university.

Triboelectric nanogenerators (TENGs) based on solution-processed zinc-oxide (ZnO) nanoripples acting as a triboelectric layer were fabricated to enhance their output voltage. Scanning electron microscopy images showed that ZnO nanoripples were uniformly formed on glass substrates coated with indium-tin oxide. The TENG containing ZnO nanoripples and operating in the vertical contact-separation mode exhibited an output voltage of 68 V, which was almost 3 times larger than that of the TENGs with ZnO nanorods. The open-circuit output voltages of TENGs were found to depend significantly on the condition of the ZnO nanoripple precursors. The friction force on the ZnO nanoripple matrix increased with increasing density of ZnO nanoripples due to an increase in the contact area between the ZnO nanoripples and the PI layer, resulting in an enhancement of the output voltage of the TENGs based on nanoripples.

The electrical characteristics of flexible memristive devices utilizing a graphene oxide (GO):polyvinylpyrrolidone (PVP) nanocomposite charge-trapping layer with a poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS)-modified layer fabricated on an indium-tin-oxide (ITO)-coated polyethylene glycol naphthalate (PEN) substrate were investigated. Current-voltage (I-V) curves for the Al/GO:PVP/PEDOT:PSS/ITO/PEN devices showed remarkable hysteresis behaviors before and after bending. The maximum memory margins of the devices before and after 100 bending cycles were approximately 7.69 × 103 and 5.16 × 102, respectively. The devices showed nonvolatile memory effect with a retention time of more than 1 × 104 s. The “Reset” voltages were distributed between 2.3 and 3.5 V, and the “Set” voltages were dispersed between −0.7 and −0.2 V, indicative of excellent, uniform electrical performance. The endurance number of ON/OFF-switching and bending cycles for the devices was 1 × 102, respectively. The bipolar resistive switching behavior was explained on the basis of I-V results. In particular, the bipolar resistive switching behaviors of the LRS and the HRS for the devices are dominated by the Ohmic and space charge current mechanisms, respectively.

Memristive devices based on cesium-lead-chlorine (CsPbCl3) perovskite quantum dots (PQDs) embedded in a poly(methyl methacrylate) (PMMA) layer were fabricated to enhance their memory stability. Current-voltage (I-V) measurements on Al/PQDs embedded in PMMA layer/indium-tin-oxide devices at 300 K showed nonvolatile rewritable memristive behaviors. The maximum ON/OFF ratio of the current bistability for the devices was as large as 2 × 104. The retention time for the devices was above 1 × 104 s, indicative of high stability of the device. The operating mechanisms of the devices related to the interaction between the PQDs and the PMMA matrix could be explained by adjusting the thickness of the active layer. Furthermore, the carrier transport mechanisms of the devices are described on the basis of the I-V results with the aid of the energy-band diagram. The carrier transport could be attributed to the space-charge-limited-current mechanism in the high resistance state and to Ohmic conduction in the low resistance state.

The effects of the ZnS shell layer on the memory performances of flexible memristive devices based on quantum dots (QDs) with an InP/ZnSe/ZnS core–multishell structure embedded in a poly(methylmethacrylate) layer were investigated. The on/off ratios of the devices based on QDs with an InP/ZnSe core–shell structure and with an InP/ZnSe/ZnS core–multishell structure were approximately 4.2 × 102 and 8.5 × 103, respectively, indicative of enhanced charge storage capability in the latter. After bending, the memory characteristics of the memristive devices based on QDs with the InP/ZnSe/ZnS structure were similar to those before bending. In addition, those devices maintained the same on/off ratios for retention time of 1 × 104 s, and the number of endurance cycles was above 1 × 102. The reset voltages ranged from −2.3 to −3.1 V, and the set voltages ranged from 1.3 to 2.1 V, indicative of reliable electrical characteristics. Furthermore, the possible operating mechanisms of the devices are presented on the basi...

Transparent and flexible photodetectors (PDs) based on CH3NH3PbI3 perovskite nanoparticles (NPs) were fabricated by using co-evaporation of methyl ammonium iodide and lead iodide. X-ray diffraction patterns and high-resolution transmission electron microscopy images demonstrated the formation of perovskite NPs. The optical transmittance of the perovskite NPs/glass was above 80% over the entire range of visible wavelengths, indicative of high transparency. The PDs based on CH3NH3PbI3 perovskite NPs were sensitive to a broad range of visible light from 450 to 650 nm. The currents in the PDs under exposure to red, green, and blue light-emitting diodes were enhanced to 5, 10, and 20 times that of the PD in the dark, respectively. The rise and the decay times of the PDs were 50 and 120 μs. The current in the perovskite NP PD on a polyethylene terephthalate substrate was enhanced by approximately 69% when the NP PD was exposed to a blue LED emitting at a wavelength of 459 nm. Despite multiple bending, the transparent and flexible PDs based on methyl ammonium iodide and lead iodide NPs showed reproducibility and high stability in performance.

Organic bistable devices (OBDs) with exfoliated mica nanoparticles (NPs) embedded into an insulating poly(methylmethacrylate) (PMMA) layer were fabricated by using a spin-coating method. Current–voltage (I–V) curves for the Al/PMMA/exfoliated mica NP/PMMA/indium-tin-oxide/glass devices at 300 K showed a clockwise current hysteresis behavior due to the existence of the exfoliated muscovite-type mica NPs, which is an essential feature for bistable devices. Write-read-erase-read data showed that the OBDs had rewritable nonvolatile memories and an endurance number of ON/OFF switching for the OBDs of 102 cycles. An ON/OFF ratio of 1 × 103 was maintained for retention times larger than 1 × 104 s. The memory mechanisms of the fabricated OBDs were described by using the trapping and the tunneling processes within a PMMA active layer containing exfoliated muscovite-type mica NPs on the basis of the energy band diagram and the I–V curves.

Wearable displays that can be applied to smart clothing systems are attracting attention as a core technology in terms of the communication between machines and humans. However, currently available displays still lack durability under random deformations of clothes. Here, we report a self-healable organic light-emitting devices (OLEDs) for smart clothing system, which can recover from the various physical deformations of clothing. The reduced luminance of damaged OLEDs can be recovered again, and the structure variation caused by repetitive motions of the OLEDs can be restored to the original shape. In addition, the operating voltage of the self-healable OLEDs is 2.9 V, which is the lowest among those reported for light-emitting devices with self-healing materials. The electroluminescence intensity at 514 nm of a damaged OLEDs is only about 14.2% of its initial value due to the formations of leakage currents around internal and external cracks. However, the electroluminescence intensity at 514 nm of a damaged device recovers to 95.3% of its initial value due to the self-healing property of the polyvinyl alcohol:Agar nanocomposite and the shape-memory property of the cross-linked polyurethane. Furthermore, we demonstrate that our newly developed self-healable OLEDs represents a new core technology for future smart clothing systems because it can self-recover from damage.

Repetitious mechanical stress or external mechanical impact can damage wearable electronic devices, leading to serious degradations in their electrical performances, which limits their applications. Because self-healing would be an excellent solution to the above-mentioned issue, this paper presents a self-healable memory device based on a novel nanocomposite layer consisting of a polyvinyl alcohol matrix and imidazole-modified graphene quantum dots. The device exhibits reliable electrical performance over 600 cycles, and the electrical properties of the device are maintained without any failure under this bending stress. Further, it is confirmed that the damaged device can recover its original electric characteristics after the self-healing process. It is believed that such outstanding results will lead the way to the realization of future wearable electronic systems.

Mimicking synaptic plasticity is a key to harnessing the power of the brain. In the present work, manganese oxide (MnO2) thin films were developed by using the simple, low-cost hydrothermal method, and the hydrothermal deposition-time-dependent resistive switching property of MnO2 thin films was investigated. The current-voltage and the charge-magnetic flux characteristics suggested that the developed devices could be placed into the category of memristive devices. The bio-synaptic properties, such as synaptic weight, potentiation depression, and symmetric Hebbian learning of these devices were demonstrated. The developed devices were able to switch between two distinctly separable resistance states and to retain the resistive switching states for 103 s without any significant degradation. In addition, their non-zero current-voltage crossing property suggests that parasitic meminductance coexists with memristive behavior. For these devices, Schottky conduction mechanisms were found to be responsible for the resistive switching effect. The results of the present investigation should be very useful for neuromorphic computing applications.

CsPbBr3 quantum dots (QDs)-NOA63 nanocomposites (NCs) are fabricated by using a UV-initiated thiol−ene “click” reaction, and the hydrophobic CsPbBr3 QDs are successfully embedded in the NOA63 matrix without chemical decomposition. The CsPbBr3 QDs-NOA63 NCs are utilized as a piezoelectric layer for piezoelectric nanogenerators (PENGs), which are compared with PENGs based on NOA63 and on CsPbBr3 QDs. The average output voltages of the PENGs based on the CsPbBr3 QDs-NOA63 NCs is significantly larger than that of the PENGs with CsPbBr3 QDs alone by a factor of 5.55. The significantly higher output voltages of the PENGs based on the CsPbBr3 QDs-NOA63 NCs is attributed to the very large piezoelectric coupling efficiency due to the utilization of NOA63. Moreover, such PENGs are found to have advantages such as an effective stress transfer, a morphology passivation effect and an enhanced piezoelectric response, and chemical compatibility with CsPbBr3 QDs.

Organic bistable light-emitting devices (OBLEDs) with an aluminum (Al)-nanoparticle-embedded tris(8-hydroxyquinoline)aluminum (Alq3) layer and double emitting layers (EMLs) were fabricated to investigate their color switching behaviors. Scanning electron microscopy images showed that Al nanoparticles were formed on the Alq3 layer. The Al nanoparticles in the Alq3 layer improved the storage margin of the organic bistable devices (OBDs), and the double EMLs changed the emission color of the organic light-emitting devices (OLEDs) according to the variations of the ON and the OFF states of the OBDs. The variations of the ON and the OFF states of the OBDs could be clearly distinguished by the color switching of the OLED. The luminances of the OBLEDs with double EMLs in the ON and the OFF states were 641.80 and 22.25 cd/m2, respectively, and their CIE coordinates at 20 V were (0.42, 0.46) and (0.51, 0.47), respectively, which corresponded to the ON and the OFF states of the OBLEDs.

The effects of taper angle of the string and the number of layers on the electrical characteristics of vertical NAND flash memories are investigated. Simulation results show that the transconductance and the threshold voltage distribution over the position of the cell along the string depend on taper angle and the number of layers. There is a taper angle that minimizes the spread of threshold voltage, and hence, the impact of the random telegraph noise and this angle depends on the number of layers. These results will be helpful in designing the vertical NAND flash memories.

Flexible nonvolatile memory (NVM) devices fabricated utilizing Au nanoparticles (AuNPs) embedded in a poly(methylmethacrylate) (PMMA) layer were fabricated on a silver nanowire (AgNW) or a poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS)/AgNW coated on poly(ethylene terephthalate) (PET) substrates. The transmittance and the sheet resistance of the PEDOT:PSS/AgNW hybrid layer were approximately 89% and 50 Ω/sq, respectively, which were comparable to the values for commercial indium-tin-oxide (ITO) electrodes. Current-voltage curves for the Al/PMMA:AuNP/PEDOT:PSS/AgNW/PET devices at 300 K showed clockwise current hysteresis behaviors due to the existence of the AuNPs. The endurance number of ON/OFF switching for the NVM devices was above 30 cycles. An ON/OFF ratio of 1 × 103 was maintained for retention times longer than 1 × 104 s. The maximum memory margins of the NVM devices before and after bending were approximately 3.4 × 103 and 1.4 × 103, respectively. The retention times of the devices before and after bending remained same 1 × 104 s. The memory margin and the stability of flexible NVMs fabricated on AgNW electrodes were enhanced due to the embedded PEDOT:PSS buffer layer.

Au-WO3 nanocomposites (NCs) were used as a hole transport layer (HTL) to enhance the power conversion efficiency (PCE) of organic photovoltaic (OPV) cells. The photon absorption of the active layer in the OPV cells was increased due to the plasmonic effect caused by the Au-WO3 NCs, resulting in an enhanced short-circuit current density for the OPV cells with the Au-WO3 NC HTL. The value of the root-mean-square roughness of the Au-WO3 NC film was smaller than that of the WO3 NP film, resulting in a more efficient transport of holes from the active layer. The PCE of the OPV cell with an Au-WO3 NCs HTL with an Au NP concentration of 10 wt% was improved by 60.37% in comparison with that with WO3 nanoparticles. The enhancement of the PCE was attributed to both an increase in the efficiency of the hole transport at an Au-WO3 NCs HTL with an Au NP concentration of 10 wt%/active layer heterointerface and an enhanced photon absorption due to the localized surface plasmon resonance effect of the Au-WO3 NCs.

Hybrid perovskite CH3NH3PbI3 has attracted extensive research interests in optoelectronic devices in recent years. Herein an inkjet printing method has been employed to deposit a perovskite CH3NH3PbI3 layer. By choosing the proper solvent and controlling the crystal growth rate, hybrid perovskite CH3NH3PbI3 nanowires, microwires, a network, and islands were synthesized by means of inkjet printing. Electrode–gap–electrode lateral-structured photodetectors were fabricated with these different crystals, of which a hybrid perovskite microwire-based photodetector would balance the uniformity and low defects to obtain a switching ratio of 16000%, responsivity of 1.2 A/W, and normalized detectivity of 2.39 × 1012 Jones at a light power density of 0.1 mW/cm2. Furthermore, the hybrid perovskite microwire-based photodetector arrays were fabricated and applied in an imaging sensor, from which the clear mapping of the light source signal was successfully obtained. This work paves the way for the realization of low-co...

Graphene quantum dots (GQDs) have currently emerged as excellent candidates for applications in GQD-based LEDs because of their potential applications in next-generation multifunctional systems. However, the numerous oxygenous functional groups and defects existing in the GQDs restrict their florescence quantum yield, resulting in a decrease in the brightness of light-emitting devices (LEDs) based on GQDs. Here, we report on solution-processed and highly-efficient LEDs that have been developed based on octadecylamine (ODA)-GQDs. In contrast with the GQDs, the number of oxygen components in the ODA-GQDs is lower due to nucleophilic substitution between the amine and the epoxy functional groups. The current and the external quantum efficiency of an LED with ODA-GQDs are 6.51 cd/A and 2.67%, respectively, this current efficiency of 6.51 cd/A being the highest among the efficiencies reported for LEDs based on GQDs. The efficiency enhancement in the LEDs with ODA-GQDs is attributed to significant improvements in the optical properties of the ODA-GQDs. The successful demonstration of this efficiency enhancement for LEDs based on ODA-GQDs indicates a potential for applications of GQD-based LEDs as next-generation real optical sources.

Wearable solar textiles have currently emerged as excellent candidates for potential applications in next-generation wearable functional clothing. Here, we report a wearable ultra-lightweight polymer solar textile based on transparent electronic fabrics (e-fabrics). The transparent e-fabrics with a structure of polyester/Ag nanowires/graphene core-shell have been used as anodes, as well as transparent substrates, for solar textiles. The anode buffer layer and the bulk heterojunction layer were deposited by blade-coating them onto the e-fabrics. The fabricated solar textiles show a power conversion efficiency of 2.27%, a low areal density of 5.0 mg/cm 2 , good endurance against mechanical deformations, and high compatibility with clothing. These results indicate that these novel solar textiles hold potential applications in the field of wearable self-powered portable electronics.

The continuously seeking of approaches for enhancing the output of triboelectric nanogenerators (TENGs) has always been the goal of researchers attempting to harvest mechanical energy efficiently. Here a novel methodology for enhancing the output performance of the TENG by introducing electron traps into the common friction layer has been firstly developed. For this purpose, reduced graphene oxide (rGO) embedded in the friction layer has been used as electron traps. Because the triboelectric electrons generated on the surface of a polyimide layer can be efficiently captured and stored in rGO sheets due to the interaction between the rGO sheets and the polyimide layer, the loss of triboelectric electrons can be suppressed. The maximum output power density of a vertical contact-separation mode TENG containing rGO sheets reached 6.3 W/m2, which was 30 times larger than that of a device without rGO sheets. We also showed that the output performance of the lateral sliding-mode TENG, which is the other fundamental working mode of the TENG, can be enhanced due to the advantage of additional electron trapping in the friction layer, indicating that the concept demonstrated in this work holds potential for providing significant enhancements in next-generation triboelectric devices.

We prepared nanocomposites of n-SnO2/p-Co3O4 for application in chemical sensors. In order to fabricate p-Co3O4-decorated n-SnO2 nanowires, we sputtered a Co layer and subsequently annealed the material in air ambient. Characterization revealed that crystalline cubic Co3O4 with a tubular-like structure was attached to the surface of SnO2 core nanowires. We carried out sensing tests at 573 K in at NO2 gas concentrations ranging between 2 and 10 ppm. The sensor response was increased both by adding the Co3O4 layer and also by decreasing the thickness of the Co3O4 layer from 19.2 to 6.4 nm. We proposed possible mechanisms to explain the enhanced sensor properties obtained by Co3O4-functionalization. Co3O4-functionalized SnO2 nanowires exhibited a higher sensor response than pristine nanowires, not only due to the heterostructure-induced depletion of n-SnO2 region but also due to the surface effects of Co3O4. The generation of hole-accumulated Co3O4 layer in case of thicker-layered nanowires will decrease the sensor response. We demonstrated that Co3O4-functionalized SnO2 nanowire sensors can be used as gas sensors at very low concentrations.

Tissue-type plasminogen activator (tPA) is the only treatment for ischemic stroke. However, tPA could induce the intracranial hemorrhage (ICH), which is the main cause of death in ischemic stroke patient after tPA treatment. At present, there is no treatment strategy to ameliorate tPA-induced brain injury after ischemia. Therefore, we investigated the effect of pre-treated isoflurane, which is a volatile anesthetic and has beneficial effects on neurological dysfunction, brain edema and infarct volume in ischemic stroke model. In this study, we used oxygen/glucose deprivation and reperfusion (OGD/R) condition to mimic an ischemic stroke in vitro. Matrix metalloproteinases (MMP) activity was measured in endothelial cell media. Also, neuronal cell culture was performed to investigate the effect of pretreated isoflurane on the neuronal cell survival after tPA-induced injury during OGD/R. Isoflurane pretreatment prevented tPA-induced MMP-2 and MMP-9 activity and suppressed tPA-triggered LRP/NF-κB/Cox-2 signaling after OGD/R. Neuronal cells, incubated with endothelial cell conditioned medium (EC-CM) after tPA + OGD/R, showed upregulation of pro-apoptotic molecules. However, neurons incubated with isoflurane-pretreated EC-CM showed increased anti-apoptotic molecules. Our findings suggest that isoflurane pretreatment could attenuate tPA-exaggerated brain ischemic injury, by reducing tPA-induced LRP/NF-κB/Cox-2 in endothelial cells, endothelial MMP-2 and MMP-9 activation, and subsequent pro-apoptotic molecule in neurons after OGD/R.

Polysilicon is commonly used as the channel in three-dimensional (3D) NAND flash memory devices. However, degradation of device performance due to grain boundary traps in the channel is a major issue. The saturation on-current level, threshold voltage (Vth), and electron density of 3D NAND flash memory devices with randomly generated grain boundaries were investigated by using three-dimensional technology computer-aided design (TCAD) simulation. The device performance tended to degrade with an increasing number of grains, and the direction of the grains significantly affected the device performance. The large decrease in the electron density of the channel region due to the direction of the grains can be explained according to the formation of the depletion region.

We developed flexible, transparent patterned electrodes, which were fabricated utilizing accelerated ultraviolet/ozone (UV/O3)-treated graphene oxide (GO)/silver nanowire (Ag-NW) nanocomposites via a simple, low-cost pattern process to investigate the feasibility of promising applications in flexible/wearable electronic and optoelectronic devices. The UV/O3 process of the GO/Ag-NW electrode was accelerated by the pre-heat treatment, and the degradation interruption of Ag NWs was removed by the GO treatment. After the deposition of the GO-treated Ag NW electrodes, the sheet resistance of the thermally annealed GO-treated Ag-NW electrodes was significantly increased by using the UV/O3 treatment, resulting in a deterioration of the GO-treated Ag NWs in areas exposed to the UV/O3 treatment. The degradation of the Ag NWs caused by the UV/O3 treatment was confirmed by using the sheet resistances, scanning electron microscopy images, X-ray photoelectron microscopy spectra, and transmittance spectra. While the sheet resistance of the low-density Ag-NW electrode was considerably increased due to the pre-thermal treatment at 90 °C for 10 min, that of the high-density Ag-NW electrode did not vary significantly even after a UV/O3 treatment for a long time. The degradation interference phenomenon caused by the UV/O3 treatment in the high-density Ag NWs could be removed by using a GO treatment, which resulted in the formation of a Ag-NW electrode pattern suitable for promising applications in flexible organic light-emitting devices. The GO treatment decreased the sheet resistance of the Ag-NW electrode and enabled the pattern to be formed by using the UV/O3 treatment. The selective degradation of Ag NWs due to UV/O3 treatment decreased the transparency of the Ag-NW electrode by about 8% and significantly increased its sheet resistance more than 100 times.

A synaptic device that functionally mimics a biological synapse is a promising candidate for use as an electronic element in a neuromorphic system. In this study, flexible electronic synaptic devices based on poly (methyl methacrylate) (PMMA):CdSe/CdZnS core-shell quantum-dot (QD) nanocomposites are demonstrated. The current-voltage characteristics for the synaptic devices under consecutive voltage sweeps show clockwise hysteresis, which is a critical feature of an artificial synaptic device. The effect of the CdSe/CdZnS QD concentration on the device performance is studied. The flexible electronic synaptic devices under bending show the similar and stable electrical performances. The memory retention measurements show that the e-synapse exhibits long-term potentiation and depression. The carrier transport mechanisms are analyzed, and thermionic emission and space-charge-limited-current conduction are found to be dominant.

The triboelectric nanogenerator (TENG) coupling contact electrification and electric induction is a landmark development in the field of energy and self-powered systems. Usually, TENGs drive light-emitting diode (LED) arrays directly to demonstrate their powerful output capabilities. However, detailed investigations of the mechanisms underlying LEDs operating at voltages much higher than those normally used have not been conducted. Here, the optical and the electrical performances of LEDs driven by TENGs are studied. Inspired by the operation mode of a TENG-driven LED, we propose a structure composed of a capacitor-LED-capacitor series, namely, LED-in-capacitors, driven by alternating current voltage. We demonstrate that the LED-in-capacitors can be directly lit by using the main power supply without a transformer and that the number of LEDs connected in series may be easily changed. In addition, due to electrostatic induction, the LED-in-capacitors can be lit wirelessly without the need for carrier injection. As a novel type of electronic device, TENG-related technology is expected to provide impetus for the development of traditional LED lighting and display technology.

Tristable switching nonvolatile memory (NVM) devices based on graphene quantum dots (GQDs) sandwiched between multi-stacked poly (methyl methacrylate) (PMMA) layers were fabricated on indium-tin-oxide (ITO)-coated glass substrates by using a solution-processed method. Current-voltage (I-V) curves at 300 K for the silver nanowire/PMMA/GQD/PMMA/GQD/PMMA/ITO/glass devices showed tristable switching currents with high-resistance, intermediate-resistance, and low-resistance states. The device's cycling endurance of the three resistance states remained stable with a distinguishable value for each resistance state over 1000 cycles, and the obtained retention results showed well-distinguished resistance states without degradation for up to 1 × 104 s. Schottky emission, Poole-Frenkel emission, trapped-charge limited-current, and ohmic conduction were proposed as the dominant conduction mechanisms for the fabricated NVM devices based on the obtained I-V characteristics. The described energy-band diagrams confirm the proposed conduction band mechanisms.

In this work, a resistance switching memory based on organic/inorganic hybrid perovskites (OIHPs) was fabricated. The CH 3 NH 3 PbI 3 perovskite was grown on polymethyl methacrylate (PMMA) as the resistance switching layer by using a two-step spin-coating procedure. The conduction mechanisms of indium-tin-oxide (ITO)/PMMA/CH 3 NH 3 PbI 3 /PMMA/Ag device were investigated in terms of current–voltage characteristics. The memory device is reprogrammable and the ON/OFF ratio reaches as high as 10 3 . Endurance cycle of the as-fabricated memory device was also carried out. The results indicate the promising electronic application of OIHPs in resistance switching memories.