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Herein, we present an unconventional method for multimodal characterization of three-dimensional cardiac organoids. This method can monitor and control the mechanophysiological parameters of organoids within a single device. In this method, local pressure distributions of human-induced pluripotent stem-cell-derived cardiac organoids are visualized spatiotemporally by an active-matrix array of pressure-sensitive transistors. This array is integrated with three-dimensional electrodes formed by the high-resolution printing of liquid metal. These liquid-metal electrodes are inserted inside an organoid to form the intraorganoid interface for simultaneous electrophysiological recording and stimulation. The low mechanical modulus and low impedance of the liquid-metal electrodes are compatible with organoids' soft biological tissue, which enables stable electric pacing at low thresholds. In contrast to conventional electrophysiological methods, this measurement of a cardiac organoid's beating pressures enabled simultaneous treatment of electrical therapeutics using a single device without any interference between the pressure signals and electrical pulses from pacing electrodes, even in wet organoid conditions.

To investigate the preoperative morphology of the foveal avascular zone (FAZ) for prediction of the postoperative visual function in advanced idiopathic epiretinal membrane (ERM). 21 patients (21 eyes) with unilateral idiopathic ERM who underwent pars plana vitrectomy (PPV) with internal limiting membrane (ILM) peeling were included. Superficial FAZ was measured preoperatively in both eyes using optical coherence tomography angiography (OCTA). Area, perimeter, and circularity of FAZ were achieved, and their rationes between the ERM eyes and the contralateral eyes were calculated to analyze the degree of FAZ distortion in diseased eyes. The best-corrected visual acuity (BCVA) and central foveal thickness (CFT) were measured at baseline and more than 6 months after surgery. The correlations of the preoperative FAZ rationes with BCVA and CFT were assessed. The FAZ in the eyes with ERM was significantly reduced, and the BCVA was significantly correlated with the area ratio (P = 0.004) and the perimeter ratio (P = 0.005) of the FAZ before surgery. Decimal BCVA changed from 0.326 ± 0.139 to 0.450 ± 0.202 (P = 0.058), and CFT reduced significantly (P = 0.001) after surgery. The preoperative FAZ area and perimeter rationes were significantly correlated with letter score gain (P = 0.001, P < 0.001), and the latter showed significant correlations with the postoperative BCVA (P = 0.031) and CFT reduction ratio (P = 0.008). The preoperative FAZ perimeter ratio is the best predictor of functional and morphological prognosis after surgery in advanced idiopathic ERM.

Purpose: To report a follow up of early intravitreal anti-vascular endothelial growth factor (VEGF) antibody treatment in a patient with maculopathy after accidental exposure to a high-powered cosmetic Nd:YAG laser.Case summary: A 36-year-old female patient visited our clinic with decreased visual acuity in the right eye after accidental exposure to a high-powered cosmetic Nd:YAG laser. The best-corrected visual acuity of the right eye was 0.1 and subretinal hemorrhage on the foveal area was observed during fundus examination. Optical coherence tomography revealed serous retinal detachment with hyperreflective disruption of the ellipsoid zone and retinal pigment epithelium-Bruch’s membrane complex. Intravitreal bevacizumab (Avastin®, 1.25 mg/0.05 mL; Roche Korea, Seoul, Korea) injections were performed three times. Visual acuity was unchanged at 6 months after the first visit. However, complete resolution of the subretinal hemorrhage was observed and there were no signs of secondary choroidal neovascularization or recurrence of choroidal hemorrhage.Conclusions: Early anti-VEGF antibody treatment in a patient with subfoveal hemorrhage and choroidal rupture after high-powered cosmetic Nd:YAG laser exposure improved morphology and prevented secondary choroidal neovascularization.

Continuous detection of raised intraocular pressure (IOP) could benefit the monitoring of patients with glaucoma. Current contact lenses with embedded sensors for measuring IOP are rigid, bulky, partially block vision or are insufficiently sensitive. Here, we report the design and testing in volunteers of a soft and transparent contact lens for the quantitative monitoring of IOP in real time using a smartphone. The contact lens incorporates a strain sensor, a wireless antenna, capacitors, resistors, stretchable metal interconnects and an integrated circuit for wireless communication. In rabbits, the lens provided measurements that match those of a commercial tonometer. In ten human participants, the lens proved to be safe, and reliably provided accurate quantitative measurements of IOP without inducing inflammation.

The brain is actuated by billions of neurons with trillions of interconnections that regulate human behaviors. Understanding the mechanisms of these systems that induce sensory reactions and respond to disease remains one of the greatest challenges in science, engineering, and medicine. Recent advances in nanomaterials and nanotechnologies have led to the extensive research of electronic devices for brain interfaces to better understand the neural activities of the brain’s complex nervous system. The development of sensor devices for monitoring the physiological signals of the brain related to traumatic injury status has accompanied by the progress of electronic neural probes in parallel. In addition, these neurological and stereotactic surgical revolutions hold immense potential for clinical analysis of pharmacological systems within cerebral tissues. Here, we review the progress of electronic devices interfacing with brain in terms of the materials, fabrication technologies, and device designs. Neurophysiological activity can be measured and modulated by brain probes based on newly developed nanofabrication methodologies. Furthermore, in vivo pathological monitoring of the brain and pharmacological assessment has been developed in miniaturized and wireless form. We also consider the key challenges and prospects for further development, and explore the future directions emerging in the latest research.

There has been a great deal of interest in designing soft robots that can mimic a human system with haptic and proprioceptive functions. There is now a strong demand for soft robots that can sense their surroundings and functions in harsh environments. This is because the wireless sensing and actuating capabilities of these soft robots are very important for monitoring explosive gases in disaster areas and for moving through contaminated environments. To develop these wireless systems, complex electronic circuits must be integrated with various sensors and actuators. However, the conventional electronic circuits based on silicon are rigid and fragile, which can limit their reliable integration with soft robots for achieving continuous locomotion. In our study, we developed an untethered, soft robotic hand that mimics human fingers. The soft robotic fingers are composed of a thermally responsive elastomer composite that includes capsules of ethanol and liquid metals for its shape deformation through an electrothermal phase transition. And these soft actuators are integrated fully with flexible forms of heaters, with pressure, temperature, and hydrogen gas sensors, and wireless electronic circuits. Entire functions of this soft hand, including the gripping motion of soft robotic fingers and the real-time detections of tactile pressures, temperatures, and hydrogen gas concentrations, are monitored or controlled wirelessly using a smartphone. This wireless sensing and actuating system for somatosensory and respiratory functions of a soft robot provides a promising strategy for next-generation robotics.

Cracked tooth syndrome (CTS) is an incomplete fracture of a human tooth that commonly arises from chewing hard foods. Although it is a very common syndrome, CTS is often difficult to diagnose owing to the common small size of tooth cracks. Conventional techniques for the detection of cracks, such as transillumination and radiographic methods, are inaccurate and have poor imaging resolution. In this study, we devise a novel method for the in vivo detection of tooth microcracks by exploiting the mechanoluminescence (ML) phenomenon. ZrO2:Ti4+ (ZRT) phosphor particles are pasted onto suspected regions of tooth cracks and emit cyan-colored light as a result of masticatory forces. Then, a stretchable and self-healable photodetector (PD) array laminated on top of the phosphor particles converts the emitted photons into a photocurrent, which facilitates the two-dimensional mapping of the tooth cracks. Because of the high photosensitivity of the PD, intense ML and small size of ZRT phosphor particles, it is possible to image submicron- to micron-sized cracks with high resolution. Furthermore, the uniqueness of this technique over the conventional techniques stems from the application of a simple optical phenomenon, i.e., ML, for obtaining precise information regarding the locations, depth, and length of tooth cracks.

To evaluate the choriocapillaris (CC) flow in central serous chorioretinopathy (CSC) and determine the relationship between CC flow void with the choroidal thickness (CT) and choroidal vascularity index (CVI).Retrospective analysis of 20 patients with CSC (40 eyes, including unaffected fellow eyes) and 20 age- and sex-matched controls. After compensation with optical coherence tomography (OCT) en-face structural image, the CC flow void (%) was measured using the phansalkar threshold with a window radius of 3 and 15 pixels. The mean CC flow voids of acute CSC, recovered-acute CSC, unaffected fellow, and control eyes were compared by matched data analysis. A regression analysis was performed on the choroidal parameters (CT and CVI) and CC flow voids.The CC flow void had an increasing tendency in the following order: control, fellow, recovered-acute CSC, and acute CSC eyes. Acute/recovered comparison showed a significant P value (0.008) in the foveal lesion. Recovered/fellow and fellow/control presented significant P values regardless of location to fovea (all0.05). There were significant positive correlations between CT and CC flow void (P 0.05) in the acute CSC, recovered-acute CSC eyes.The CC flow on OCT angiography decreased in acute CSC eyes, especially in the foveal lesion, with a published compensation method. The findings suggest that unmodulated choroidal blood flow contributed to partially reversible diminished CC flow.

Recent approaches in self-healable electrodes use polymers with exhibiting significantly low electrical conductivity, compared to conventional metals. Such self-healable electrodes also require external stimuli to initiate self-healing, or present slow restoration for their intrinsic healing. Herein, we introduce an instantaneous and repeatable self-healing of highly conductive, fully metallic electrodes at ambient conditions. These electrodes consist of silver and liquid metal (with no polymer), and exhibit a sufficiently high conductivity of 2 S/μm. The liquid metal (LM) component enables instantaneous and repeatable self-healing of these electrodes (within a few milliseconds) under no external energy as well as high stretchability. Additionally, the inclusion of silver in this LM improves the mechanical strength of this composite, thereby overcoming the limitation of a pristine LM that has low mechanical strength. Moreover, this composite formation can be effective in preventing the penetration of gallium atoms into different metals, while preserving electrical contact properties. Also the self-healable nature of electrodes enables their outstanding sustainability against electrical breakdown at relatively high electric fields. Furthermore, the compatibility of these self-healable electrodes with conventional photolithography and wet etching facilitates high-resolution patterning for device fabrications, as demonstrated in an example with a self-healable organic light-emitting diode display.

Integration of a smart contact lens and a heat patch realizes personal management of ocular surface diseases wirelessly., Wearable electronic devices that can monitor physiological signals of the human body to provide biomedical information have been drawing extensive interests for sustainable personal health management. Here, we report a human pilot trial of a soft, smart contact lens and a skin-attachable therapeutic device for wireless monitoring and therapy of chronic ocular surface inflammation (OSI). As a diagnostic device, this smart contact lens enables real-time measurement of the concentration of matrix metalloproteinase-9, a biomarker for OSI, in tears using a graphene field-effect transistor. As a therapeutic device, we also fabricated a stretchable and transparent heat patch attachable on the human eyelid conformably. Both diagnostic and therapeutic devices can be incorporated using a smartphone for their wireless communications, thereby achieving instantaneous diagnosis of OSI and automated hyperthermia treatments. Furthermore, in vivo tests using live animals and human subjects confirm their good biocompatibility and reliability as a noninvasive, mobile health care solution.

Despite recent substantial advances in perovskite materials, their 3D integration capability for next-generation electronic devices is limited owing to their inherent vulnerability to heat and moisture with degradation of their remarkable optoelectronic properties during fabrication processing. Herein, a facile method to transfer the patterns of perovskites to planar or nonplanar surfaces using a removable polymer is reported. After fabricating perovskite devices on this removable polymer film, the conformal attachment of this film on target surfaces can place the entire devices on various substrates by removing this sacrificial film. This transfer method enables the formation of a perovskite image sensor array on a soft contact lens, and in vivo tests using rabbits demonstrate its wearability. Furthermore, 3D heterogeneous integration of a perovskite photodetector array with an active-matrix array of pressure-sensitive silicon transistors using this transfer method demonstrates the formation of a multiplexed sensing platform detecting distributions of light and tactile pressure simultaneously.

Wearable healthcare devices have garnered substantial interest for the realization of personal health management by monitoring the physiological parameters of individuals. Attaining the integrity between the devices and the biological interfaces is one of the greatest challenges to achieving high-quality body information in dynamic conditions. Liquid metals, which exist in the liquid phase at room temperatures, are advanced intensively as conductors for deformable devices because of their excellent stretchability and self-healing ability. The unique surface chemistry of liquid metals allows the development of various sensors and devices in wearable form. Also, the biocompatibility of liquid metals, which is verified through numerous biomedical applications, holds immense potential in uses on the surface and inside of a living body. Here, the recent progress of liquid metal-based wearable electronic devices for healthcare with respect to the featured properties and the processing technologies is discussed. Representative examples of applications such as biosensors, neural interfaces, and a soft interconnection for devices are reviewed. The current challenges and prospects for further development are also discussed, and the future directions of advances in the latest research are explored.

Purpose To evaluate changes in choroidal vascular structure and aqueous cytokine levels in eyes with vitreoretinal lymphoma (VRL) after intravitreal methotrexate (MTX) treatment. Methods In this retrospective study, VRL patients who visited our hospital between October 2018 and July 2020 were reviewed. Aqueous samples were obtained before treatment and at clinical resolution after intravitreal MTX therapy. Interleukin (IL)-6 and IL-10 levels and the IL-10-to-IL-6 ratio were evaluated. Swept-source optical coherence tomographic images were obtained along with the aqueous samples. Subfoveal choroidal thickness (SFCT), total vascular area of the choroid (TCA), stromal area (SA), luminal area (LA), and choroidal vascularity index (CVI) were assessed. Results Twelve patients were enrolled (female:male—5:7). The mean age (± standard deviation) at diagnosis was 60.9±8.5 years. In the 16 eyes diagnosed with VRL, values of SFCT, TCA, LA, and SA significantly decreased after treatment (all p-values Conclusion Eyes with active VRL exhibited choroidal thickening with increased vascular and stromal areas that decreased after remission following MTX treatment. Higher aqueous IL-10 and IL-6 levels and lower visual acuity in the active phase may indicate the number of injections required for remission; this should be considered in the treatment of patients with VRL.

This study presents a smart, soft contact lens that provides real-time sensing for the wireless immunosensing of cortisol., Despite various approaches to immunoassay and chromatography for monitoring cortisol concentrations, conventional methods require bulky external equipment, which limits their use as mobile health care systems. Here, we describe a human pilot trial of a soft, smart contact lens for real-time detection of the cortisol concentration in tears using a smartphone. A cortisol sensor formed using a graphene field-effect transistor can measure cortisol concentration with a detection limit of 10 pg/ml, which is low enough to detect the cortisol concentration in human tears. In addition, this soft contact lens only requires the integration of this cortisol sensor with transparent antennas and wireless communication circuits to make a smartphone the only device needed to operate the lens remotely without obstructing the wearer’s view. Furthermore, in vivo tests using live rabbits and the human pilot experiment confirmed the good biocompatibility and reliability of this lens as a noninvasive, mobile health care solution.

Dipole layers can be formed at epitaxial interfaces of perovskite oxides by intentionally inserting charged atomic layers. Perovskite oxides such as SrTiO3 (STO) can provide dielectrics with very high dielectric constants, but their bandgaps are so small that the suppression of leakage current is one of the critical issues when they are applied for DRAM capacitors. However, their conduction band offset will be manipulated if we can control the dipole layer formation. In this study, we investigated the opportunities of band alignment manipulation using the interface dipole effect especially focusing on the number of charge-introducing atomic layers. STO/LaAlO3 (LAO)/SrRuO3(SRO) stacks were fabricated by pulsed laser deposition method, to demonstrate the modulation of the band alignment at STO/SRO interface as large as ± 0.5 eV, when we change the number of inserted atomic layers of LAO.

We report an Ag nanofiber-embedded glass-fabric reinforced hybrimer (AgNF-GFRHybrimer) composite film as a reliable and high-performance flexible transparent conducting film. The continuous AgNF network provides superior optoelectronic properties of the composite film by minimizing transmission loss and junction resistance. In addition, the excellent thermal/chemical stability and mechanical durability of the GFRHybrimer matrix provides enhanced mechanical durability and reliability of the final AgNF-GFRHybrimer composite film. To demonstrate the availability of our AgNF-GFRHybrimer composite as a transparent conducting film, we fabricated a flexible organic light-emitting diode (OLED) device on the AgNF-GFRHybrimer film; the OLED showed stable operation during a flexing.

Research of flexible and stretchable electronic devices has shown remarkable development due to the remarkable characteristics of graphene. To exploit these characteristics, many devices have been developed using graphene-based hybrid materials or structures. In this paper, we present the electrical, optical, thermal, and mechanical properties of graphene and then provide information concerning the various electronic devices fabricated using graphene and its hybrid materials or structures, with special emphasis on stretchable devices.

Label-free, nanoparticle-based plasmonic optical biosensing, combined with device miniaturization and microarray integration, has emerged as a promising approach for rapid, multiplexed biomolecular analysis. However, limited sensitivity prevents the wide use of such integrated label-free nanoplasmonic biosensors in clinical and life science applications where low-abundance biomolecule detection is needed. Here, we present a nanoplasmofluidic device integrated with microelectrodes for rapid, label-free analysis of a low-abundance cell signaling protein, detected by AC electroosmosis-enhanced localized surface plasmon resonance (ACE-LSPR) biofunctional nanoparticle imaging. The ACE-LSPR device is constructed using both bottom-up and top-down sensor fabrication methods, allowing the seamless integration of antibody-conjugated gold nanorod (AuNR) biosensor arrays with microelectrodes on the same microfluidic platform. Applying an AC voltage to microelectrodes while scanning the scattering light intensity variation of the AuNR biosensors results in significantly enhanced biosensing performance. The AC electroosmosis (ACEO) based enhancement of the biosensor performance enables rapid (5–15 min) quantification of IL-1β, a pro-inflammatory cytokine biomarker, with a sensitivity down to 158.5 fg/mL (9.1 fM) for spiked samples in PBS and 1 pg/mL (58 fM) for diluted human serum. Together with the optimized detection sensitivity and speed, our study presents the first critical step toward the application of nanoplasmonic biosensing technology to immune status monitoring guided by low-abundance cytokine measurement.

Continuous detection of raised intraocular pressure (IOP) could benefit the monitoring of patients with glaucoma. Current contact lenses with embedded sensors for measuring IOP are rigid, bulky, partially block vision or are insufficiently sensitive. Here, we report the design and testing in volunteers of a soft and transparent contact lens for the quantitative monitoring of IOP in real time using a smartphone. The contact lens incorporates a strain sensor, a wireless antenna, capacitors, resistors, stretchable metal interconnects and an integrated circuit for wireless communication. In rabbits, the lens provided measurements that match those of a commercial tonometer. In ten human participants, the lens proved to be safe, and reliably provided accurate quantitative measurements of IOP without inducing inflammation.

In recent studies related to bioelectronics, significant efforts have been made to form 3D electrodes to increase the effective surface area or to optimize the transfer of signals at tissue-electrode interfaces. Although bioelectronic devices with 2D and flat electrode structures have been used extensively for monitoring biological signals, these 2D planar electrodes have made it difficult to form biocompatible and uniform interfaces with nonplanar and soft biological systems (at the cellular or tissue levels). Especially, recent biomedical applications have been expanding rapidly toward 3D organoids and the deep tissues of living animals, and 3D bioelectrodes are getting significant attention because they can reach the deep regions of various 3D tissues. An overview of recent studies on 3D bioelectronic devices, such as the use of electrical stimulations and the recording of neural signals from biological subjects, is presented. Subsequently, the recent developments in materials and fabrication processing to 3D micro- and nanostructures are introduced, followed by broad applications of these 3D bioelectronic devices at various in vitro and in vivo conditions.

The recent advent of unprecedented wearable applications engendered the need for stretchable electronics, which can be realized by making the individual components stretchable. The transparent conducting electrode is one of the most important components of optoelectronic devices. Therefore, developing transparent electrodes in a stretchable form is essential for the implementation of stretchable electronics. In this paper, the recent efforts in the development of stretchable and transparent electrodes, particularly those using nanomaterials such as metal nanowires, metal nanofibers, and carbon nanotubes are introduced.

High-resolution, 3D reconfiguration method using liquid metals is studied for stretchable 3D integrations in electronics., We report an unconventional approach for high-resolution, reconfigurable 3D printing using liquid metals for stretchable, 3D integrations. A minimum line width of 1.9 μm can be reliably formed using direct printing, and printed patterns can be reconfigured into diverse 3D structures with maintaining pristine resolutions. This reconfiguration can be performed multiple times, and it also generates a thin oxide interface that can be effective in preventing the spontaneous penetration of gallium atoms into different metal layers while preserving electrical properties under ambient conditions. Moreover, these free-standing features can be encapsulated with stretchable, conformal passivations. We demonstrate applications in the form of a reconfigurable antenna, which is tunable by changing geometeries, and reversibly movable interconnections used as mechanical switches. The free-standing 3D structure of electrodes is also advantageous for minimizing the number and space between interconnections, which is important for achieving higher integrations, as demonstrated in an array of microLEDs.

We report a high-performance, flexible and robust metal nanotrough-embedded transparent conducting hybrid film (metal nanotrough-GFRHybrimer). Using an electro-spun polymer nanofiber web as a template and vacuum-deposited gold as a conductor, a junction resistance-free continuous metal nanotrough network is formed. Subsequently, the metal nanotrough is embedded on the surface of a glass-fabric reinforced composite substrate (GFRHybrimer). The monolithic composite structure of our transparent conducting film allows simultaneously high thermal stability (24 h at 250 °C in air), a smooth surface topography (Rrms < 1 nm) and excellent opto-electrical properties. A flexible touch screen panel (TSP) is fabricated using the transparent conducting films. The flexible TSP device stably operates on the back of a human hand and on a wristband.

In all the previously reported 4,8-dithienylbenzo[1,2-b:4,5-b′]dithiophene (DTBDT)-based π-conjugated polymers, the polymerization and two-dimensional (2D) conjugation extension pathways were through the thiophenes fused to the phenyl core of DTBDT and through the thiophenes linked to the benzene core of DTBDT, respectively (BDT-directed DTBDT). Herein, with the aim of discovering another potential way to introduce the DTBDT motif in the donor–acceptor alternating polymer structure, we first report the synthesis of three new π-conjugated polymers, P1, P2, and P3, with a modified DTBDT building block as a donor unit. This modification results in new polymerization and 2D conjugation extension pathways for the polymers through the thiophenes linked to the benzene core of DTBDT and through the thiophenes fused to the phenyl core of the DTBDT, respectively (dithienylbenzene-directed DTBDT). Although these modified polymerization pathways of DTBDT result in less delocalized conjugation along the dithienylbenze...

π-spacers and alkyl side chains play a key role in the optical, electrochemical, and photovoltaic properties of π-conjugated polymers. To investigate the collective effects of π-spacers, alkyl side chains, and various processing conditions on the photovoltaic properties, an array of four new low bandgap (LBG) π-conjugated polymers (P1–P4) was designed and synthesized for their application as donor materials in bulk heterojunction polymer solar cells (BHJ PSCs). These π-conjugated polymers contain a benzodithiophene (BDT) donor unit substituted with 2-ethylhexylselenyl or 2-hexyldecylselenyl as π-conjugated side chains and a dialkoxybenzothiadiazole (dialkoxyBT) electron deficient unit connected with thiophene or selenophene as π-spacers. Among the four polymers, the absorption spectra of P3 with the thiophene π-spacer showed a well enhanced vibronic shoulder peak between 620 and 650 nm, indicating that P3 possesses a strong interchain aggregation tendency and attains a planar backbone structure due to the non-covalent interactions arising between the sulfur atom in thiophene and the oxygen atom in dialkoxyBT. Under suitable device processing conditions optimized pristine PSCs of P3 showed a maximum power conversion efficiency (PCE) of 4.09%. After employing 1,8-diiodooctane as an additive, one of the PSC devices based on P2 displayed a PCE of 5.34%. The active layers of P1–P4 showed a positive response towards methanol treatment, especially the P3-based devices delivered an improved PCE of 5.63%, which was further assessed by electrical impedance spectroscopy. These findings in the current article provide a good specimen for efficiently fine tuning the optical and photovoltaic properties of π-conjugated polymers via varying the size of alkyl chains, π-spacer groups and device processing conditions for the imminent growth of LBG π-conjugated polymers.

Wearable human interaction devices are technologies with various applications for improving human comfort, convenience and security and for monitoring health conditions. Healthcare monitoring includes caring for the welfare of every person, which includes early diagnosis of diseases, real-time monitoring of the effects of treatment, therapy, and the general monitoring of the conditions of people’s health. As a result, wearable electronic devices are receiving greater attention because of their facile interaction with the human body, such as monitoring heart rate, wrist pulse, motion, blood pressure, intraocular pressure, and other health-related conditions. In this paper, various smart sensors and wireless systems are reviewed, the current state of research related to such systems is reported, and their detection mechanisms are compared. Our focus was limited to wearable and attachable sensors. Section 1 presents the various smart sensors. In Section 2, we describe multiplexed sensors that can monitor several physiological signals simultaneously. Section 3 provides a discussion about short-range wireless systems including bluetooth, near field communication (NFC), and resonance antenna systems for wearable electronic devices.

Two new heteroleptic blue emitting Ir(III) complexes, EtOCN-FIracac and tBuCN-FIracac, and a homoleptic Ir(III) complex, tBu-FCNIr, consisting of 2′,4″-difluorophenylpyridine (dfppy) with a cyano (CN) group at the 5′ position of the phenyl and an ethoxy (EtO-) or tert-butyl (tBu) group at the 4 position of the pyridine as the main ligands, are synthesized and characterized for phosphorescent organic light-emitting diodes (PhOLEDs). The dual functionalization of the dfppy core with the electron-withdrawing CN and electron-donating EtO- or tBu- groups leads to improved blue color purity by compensating the bathochromic shift originating from the ancillary ligand of the heteroleptic Ir(III) complex and contributes to the enhancement of the horizontal ratio of emitting dipoles (Θ), which is one of the promising approaches to improve the efficiency of PhOLEDs. PhOLEDs based on tBuCN-FIracac and EtOCN-FIracac show one of the highest efficiencies ever achieved for blue color, with maximum external quantum efficiencies (EQEs) of 22.3% (39.2 cd A−1) and 21.5% (35.1 cd A−1), respectively, with a simple device structure; a similar device based on tBu-FCNIr displays a maximum EQE of 16.2% (23.5 cd A−1). The performance of PhOLEDs based on the two heteroleptic Ir(III) complexes are highly improved compared to tBu-FCNIr, due to the increased θ and photoluminescence quantum yield (PLQY).

A new series of highly efficient Ir(III) complexes, (DPQ) 2 Ir(pic-N-O), (F 4 PPQ) 2 Ir(pic-N-O), (FPQ) 2 Ir(pic-N-O), and (CPQ) 2 Ir(pic-N-O) were synthesized for phosphorescent organic light-emitting diodes (PhOLEDs), and their photophysical, electrochemical, and electroluminescent (EL) properties were investigated. The Ir(III) complexes, including picolinic acid N-oxide (pic-N-O) ancillary ligand, are comprised with the various main ligands such as 2,4-diphenylquinoline (DPQ), 4-phenyl-2-(2,3,4,5-tetrafluorophenyl)quinoline (F 4 PPQ), 2-(9,9-diethyl-9H-fluoren-2-yl)-4-phenylquinoline (FPQ) and 9-ethyl-3-(4-phenylquinolin-2-yl)-9H-carbazole. Remarkably, high performance PhOLEDs using a solution-processable (DPQ) 2 Ir(pic-N-O) doped CBP host emission layer were fabricated to give a high luminance efficiency (LE) of 26.9 cd/A, equivalent to an external quantum efficiency (EQE) of 14.2%. The calculated HOMO–LUMO energy gaps for (DPQ) 2 Ir(pic-N-O), (F 4 PPQ) 2 Ir(pic-N-O), (FPQ) 2 Ir(pic-N-O) and (CPQ) 2 Ir(pic-N-O) were in good agreement with the experimental results.

Coumarin dyes containing a low band-gap chromophore of benzothiadiazole, which comprises a coumarin moiety as the electron donor and a cyanoacrylic acid moiety as electron acceptor in D–A–π–A system, were developed to use in dye-sensitised solar cells (DSSCs). The introduction of the benzothiadiazole unit into the molecular framve distinctly narrowed the band-gap between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO), so that the absorption peak was red-shifted. As a result, a solar cell based on the HKK-CM4 sensitiser showed better photovoltaic performance with a J SC of 14.3 mA cm −2 , a V OC of 0.58 V, and an FF of 0.72, corresponding to an overall conversion efficiency η of 5.97% under standard AM 1.5 irradiation.

It has recently been shown that the types of intramolecular magnetic interactions of diradical systems can be changed by the types of radical group: syn-group (or α-group) and anti-group (or β-group). The aim of this study is to establish a useful scheme to understand and explain the intramolecular magnetic interactions in diradical systems regardless of radical groups and the topology of a coupler. We investigated the intramolecular magnetic coupling constant (J) of six oxoverdazyl diradicals (i-vi) coupled with a benzene ring based on the unrestricted DFT calculations. On the basis of our results, we devised a simple but useful scheme by combining the spin alternation rule and the concept of radical group classification. Consequently, it was found that the calculated J values and plots of spin density distributions were consistent with our proposed scheme. In addition, we discussed the closed-shell singlet (CS) state and the dihedral angle effect on J values in detail to comprehensively understand the magnetic interactions of diradical systems. Our scheme can provide the basic framework to design future organic high-spin molecules and organic magnetic materials.

An oxadiazole based electron transporting (ET) unit was glued to the heteroleptic Ir(III) complex (TPQIr-ET) and used as a dopant for phosphorescent organic light-emitting diodes (PhOLEDs). It shows superior device performance than the dopant without the ET unit (TPQIr) due to the balanced charge carrier injection by the ET unit.

This paper reports the effects of thermal energy on reducing the overshoot of the current sweep cycle method to reduce the screening current-induced field (SCF) in a 2G high temperature superconducting (HTS) coil. A disadvantage of the current sweep cycle method is the necessity for large overshoot in the coil current. For a 2G HTS coil, excessive overshooting of the coil current is undesirable (Yanagisawa et al 2012 AIP Conf. Proc. 1434 1373–8). In an effort to circumvent this overshooting problem, the thermal energy effect was investigated in combination with the current sweep cycle method based on experiments in this study. The experimental results show that greater SCF reduction in the HTS coil was obtained upon increasing thermal energy by heater current.

To overcome the limitation of conventional carbon nanotube fabrication techniques, inkjet printing was directly utilized on a whole wafer. In this work, inkjet printing method was used as a strong technique for the massive production of gas sensor applications. As a single wafer processing, it provided the great potential to fabricate uniform and reproducible single walled carbon nanotube (SWCNT) films on desired positions in terms of electrical characteristics and gas reaction performances. In order to secure good electrical contact between SWCNTs and the metal electrode, SWCNTs were firstly printed on a wafer with insulation layer, and then the metal electrodes were patterned by using lift-off process. The fabricated gaps of the electrodes were 2, 4, and 8 m, respectively. SWCNT films contacted tightly beneath the electrode show low and uniform electrical resistance values of 96-281 and reliable gas detection performances as well. In this work, As-deposited devices exhibit about 3% sensitivities to 100ppb - NO2 in 10 minutes and increased up to 9% by the annealing treatments at 400degC.