Vertical full-colour micro-LEDs via 2D materials-based layer transfer.

Micro-LEDs (µLEDs) have been explored for augmented and virtual reality display applications that require extremely high pixels per inch and luminance1,2. However, conventional manufacturing processes based on the lateral assembly of red, green and blue (RGB) µLEDs have limitations in enhancing pixel density3-6. Recent demonstrations of vertical µLED displays have attempted to address this issue by stacking freestanding RGB LED membranes and fabricating top-down7-14, but minimization of the lateral dimensions of stacked µLEDs has been difficult. Here we report full-colour, vertically stacked µLEDs that achieve, to our knowledge, the highest array density (5,100 pixels per inch) and the smallest size (4 µm) reported to date. This is enabled by a two-dimensional materials-based layer transfer technique15-18 that allows the growth of RGB LEDs of near-submicron thickness on two-dimensional material-coated substrates via remote or van der Waals epitaxy, mechanical release and stacking of LEDs, followed by top-down fabrication. The smallest-ever stack height of around 9 µm is the key enabler for record high µLED array density. We also demonstrate vertical integration of blue µLEDs with silicon membrane transistors for active matrix operation. These results establish routes to creating full-colour µLED displays for augmented and virtual reality, while also offering a generalizable platform for broader classes of three-dimensional integrated devices.

Skin electronics from scalable fabrication of an intrinsically stretchable transistor array.

Skin-like electronics that can adhere seamlessly to human skin or within the body are highly desirable for applications such as health monitoring, medical treatment, medical implants and biological studies, and for technologies that include human-machine interfaces, soft robotics and augmented reality. Rendering such electronics soft and stretchable-like human skin-would make them more comfortable to wear, and, through increased contact area, would greatly enhance the fidelity of signals acquired from the skin. Structural engineering of rigid inorganic and organic devices has enabled circuit-level stretchability, but this requires sophisticated fabrication techniques and usually suffers from reduced densities of devices within an array. We reasoned that the desired parameters, such as higher mechanical deformability and robustness, improved skin compatibility and higher device density, could be provided by using intrinsically stretchable polymer materials instead. However, the production of intrinsically stretchable materials and devices is still largely in its infancy: such materials have been reported, but functional, intrinsically stretchable electronics have yet to be demonstrated owing to the lack of a scalable fabrication technology. Here we describe a fabrication process that enables high yield and uniformity from a variety of intrinsically stretchable electronic polymers. We demonstrate an intrinsically stretchable polymer transistor array with an unprecedented device density of 347 transistors per square centimetre. The transistors have an average charge-carrier mobility comparable to that of amorphous silicon, varying only slightly (within one order of magnitude) when subjected to 100 per cent strain for 1,000 cycles, without current-voltage hysteresis. Our transistor arrays thus constitute intrinsically stretchable skin electronics, and include an active matrix for sensory arrays, as well as analogue and digital circuit elements. Our process offers a general platform for incorporating other intrinsically stretchable polymer materials, enabling the fabrication of next-generation stretchable skin electronic devices.

Intrinsically stretchable and healable semiconducting polymer for organic transistors.

Thin-film field-effect transistors are essential elements of stretchable electronic devices for wearable electronics. All of the materials and components of such transistors need to be stretchable and mechanically robust. Although there has been recent progress towards stretchable conductors, the realization of stretchable semiconductors has focused mainly on strain-accommodating engineering of materials, or blending of nanofibres or nanowires into elastomers. An alternative approach relies on using semiconductors that are intrinsically stretchable, so that they can be fabricated using standard processing methods. Molecular stretchability can be enhanced when conjugated polymers, containing modified side-chains and segmented backbones, are infused with more flexible molecular building blocks. Here we present a design concept for stretchable semiconducting polymers, which involves introducing chemical moieties to promote dynamic non-covalent crosslinking of the conjugated polymers. These non-covalent crosslinking moieties are able to undergo an energy dissipation mechanism through breakage of bonds when strain is applied, while retaining high charge transport abilities. As a result, our polymer is able to recover its high field-effect mobility performance (more than 1 square centimetre per volt per second) even after a hundred cycles at 100 per cent applied strain. Organic thin-film field-effect transistors fabricated from these materials exhibited mobility as high as 1.3 square centimetres per volt per second and a high on/off current ratio exceeding a million. The field-effect mobility remained as high as 1.12 square centimetres per volt per second at 100 per cent strain along the direction perpendicular to the strain. The field-effect mobility of damaged devices can be almost fully recovered after a solvent and thermal healing treatment. Finally, we successfully fabricated a skin-inspired stretchable organic transistor operating under deformations that might be expected in a wearable device.

Multi-scale ordering in highly stretchable polymer semiconducting films.

Stretchable semiconducting polymers have been developed as a key component to enable skin-like wearable electronics, but their electrical performance must be improved to enable more advanced functionalities. Here, we report a solution processing approach that can achieve multi-scale ordering and alignment of conjugated polymers in stretchable semiconductors to substantially improve their charge carrier mobility. Using solution shearing with a patterned microtrench coating blade, macroscale alignment of conjugated-polymer nanostructures was achieved along the charge transport direction. In conjunction, the nanoscale spatial confinement aligns chain conformation and promotes short-range π-π ordering, substantially reducing the energetic barrier for charge carrier transport. As a result, the mobilities of stretchable conjugated-polymer films have been enhanced up to threefold and maintained under a strain up to 100%. This method may also serve as the basis for large-area manufacturing of stretchable semiconducting films, as demonstrated by the roll-to-roll coating of metre-scale films.

Partially-Screened Field Effect and Selective Carrier Injection at Organic Semiconductor/Graphene Heterointerface.

Due to the lack of a bandgap, applications of graphene require special device structures and engineering strategies to enable semiconducting characteristics at room temperature. To this end, graphene-based vertical field-effect transistors (VFETs) are emerging as one of the most promising candidates. Previous work attributed the current modulation primarily to gate-modulated graphene-semiconductor Schottky barrier. Here, we report the first experimental evidence that the partially screened field effect and selective carrier injection through graphene dominate the electronic transport at the organic semiconductor/graphene heterointerface. The new mechanistic insight allows us to rationally design graphene VFETs. Flexible organic/graphene VFETs with bending radius <1 mm and the output current per unit layout area equivalent to that of the best oxide planar FETs can be achieved. We suggest driving organic light emitting diodes with such VFETs as a promising application.

Understanding polymorphism in organic semiconductor thin films through nanoconfinement.

Understanding crystal polymorphism is a long-standing challenge relevant to many fields, such as pharmaceuticals, organic semiconductors, pigments, food, and explosives. Controlling polymorphism of organic semiconductors (OSCs) in thin films is particularly important given that such films form the active layer in most organic electronics devices and that dramatic changes in the electronic properties can be induced even by small changes in the molecular packing. However, there are very few polymorphic OSCs for which the structure-property relationships have been elucidated so far. The major challenges lie in the transient nature of metastable forms and the preparation of phase-pure, highly crystalline thin films for resolving the crystal structures and evaluating the charge transport properties. Here we demonstrate that the nanoconfinement effect combined with the flow-enhanced crystal engineering technique is a powerful and likely material-agnostic method to identify existing polymorphs in OSC materials and to prepare the individual pure forms in thin films at ambient conditions. With this method we prepared high quality crystal polymorphs and resolved crystal structures of 6,13-bis(triisopropylsilylethynyl)pentacene (TIPS-pentacene), including a new polymorph discovered via in situ grazing incidence X-ray diffraction and confirmed by molecular mechanic simulations. We further correlated molecular packing with charge transport properties using quantum chemical calculations and charge carrier mobility measurements. In addition, we applied our methodology to a [1]benzothieno[3,2-b][1]1benzothiophene (BTBT) derivative and successfully stabilized its metastable form.

Orthostatic hypotension, non-dipping and striatal dopamine in Parkinson disease.

Orthostatic hypotension and non-dipping are relatively common autonomic dysfunctions in patients with Parkinson disease (PD). These abnormalities have been thought to occur independently of striatal dopaminergic depletion; however, only little preliminary information is available. In this study, we investigated the association of neurocirculatory changes with striatal dopamine transporter status in 69 patients with early PD. Seventeen patients had orthostatic hypotension and 55 patients were non-dippers. A comparison between cases with and without orthostatic hypotension was insignificant for striatal dopamine transporter uptake. These insignificances continued in a comparison of dippers and non-dippers. These results suggest that sympathetic noradrenergic dysfunctions in PD are independent of striatal dopamine transporter depletion.

Efficacy of Poria Cocos Extract on Sleep Quality Enhancement: A Clinical Perspective with Implications for Functional Foods.

BACKGROUND: Since the outbreak of the pandemic started, an increase in the number of sleep disorders, including insomnia and poor sleep quality, has been seen. The pattern will probably continue. METHODS: This study focuses on the preparation and clinical testing of Poria cocos extract in treating suboptimal sleep quality. The optimal extraction method utilized a 75% ethanol concentration, and the clinical investigation involved subjects with defined poor sleep taking 800 mg of the extract nightly, assessed using the Sleep Questionnaire and polysomnography. The non-parametric Wilcoxon signed-rank test was used for statistical analysis due to the non-normal distribution of the collected data. RESULTS: The study involved 21 insomnia sufferers with a mean age of 55 who were administered Poria cocos extracts. The findings of the study indicate a statistically significant rise in the overall duration of sleep (from 327.395 ± 43.2 min to 356.516 ± 63.21 min, p = 0.014). Additionally, there was a notable decrease in the level of arousal during sleep (from 76.316 ± 44.78 min to 47.989 ± 42.38 min, p = 0.009), and an improvement in the sleep severity index of the sleep questionnaire test. CONCLUSIONS: Poria cocos as a natural substance could improve quality of sleep, based on the findings. The study investigates Pachymic acid, a substance found in Poria cocos, as a potential indicator for the development of sleeping aids.

Applications of remote epitaxy and van der Waals epitaxy.

Epitaxy technology produces high-quality material building blocks that underpin various fields of applications. However, fundamental limitations exist for conventional epitaxy, such as the lattice matching constraints that have greatly narrowed down the choices of available epitaxial material combinations. Recent emerging epitaxy techniques such as remote and van der Waals epitaxy have shown exciting perspectives to overcome these limitations and provide freestanding nanomembranes for massive novel applications. Here, we review the mechanism and fundamentals for van der Waals and remote epitaxy to produce freestanding nanomembranes. Key benefits that are exclusive to these two growth strategies are comprehensively summarized. A number of original applications have also been discussed, highlighting the advantages of these freestanding films-based designs. Finally, we discuss the current limitations with possible solutions and potential future directions towards nanomembranes-based advanced heterogeneous integration.

A low-power stretchable neuromorphic nerve with proprioceptive feedback.

By relaying neural signals from the motor cortex to muscles, devices for neurorehabilitation can enhance the movement of limbs in which nerves have been damaged as a consequence of injuries affecting the spinal cord or the lower motor neurons. However, conventional neuroprosthetic devices are rigid and power-hungry. Here we report a stretchable neuromorphic implant that restores coordinated and smooth motions in the legs of mice with neurological motor disorders, enabling the animals to kick a ball, walk or run. The neuromorphic implant acts as an artificial efferent nerve by generating electrophysiological signals from excitatory post-synaptic signals and by providing proprioceptive feedback. The device operates at low power (~1/150 that of a typical microprocessor system), and consists of hydrogel electrodes connected to a stretchable transistor incorporating an organic semiconducting nanowire (acting as an artificial synapse), connected via an ion gel to an artificial proprioceptor incorporating a carbon nanotube strain sensor (acting as an artificial muscle spindle). Stretchable electronics with proprioceptive feedback may inspire the further development of advanced neuromorphic devices for neurorehabilitation.

Application of Static Headspace GC-MS Method for Selective 1,4-Dioxane Detection in Food Additives.

Efficient detection methods must be developed for 1,4-dioxane due to its suspected status as a human carcinogen, which is highly mobile in food and environmental resources. In this regard, this experiment has been conducted to develop reliable and selective detection and measurement methods by using static headspace (SH) isolation, followed by gas chromatography-mass spectrometry (GC-MS). A new method was developed for determining the spiked 1,4-dioxane contents in a polyethylene glycol 600 (PEG 600). The optimal condition for SH-GC-MS was discussed. The representative ions of 1,4-dioxane and 1,4-dioxane-d8 in the SIM mode of MS are 88 and 96, respectively, and the peaks of the SIM mode were separated and confirmed. The linear range for the method covers 0.25 to 100 mg/L with a coefficient of determination (R2) ≥ 0.999. The method applicability was demonstrated by spike recovery across a variety of food additives (i.e., chlorine bitartrate, choline chloride, polysorbate 20 and 60, and PEG 1000). All spike recovery from the tested samples was in the range of 89.50-102.68% with a precision of 0.44-11.22%. These findings suggest a new analytical method for food safety inspection, and could be applicable for ensuring the safety of foods and environmental and public health on a broad scale.

A Hemispherical Image Sensor Array Fabricated with Organic Photomemory Transistors.

Hemispherical image sensors simplify lens designs, reduce optical aberrations, and improve image resolution for compact wide-field-of-view cameras. To achieve hemispherical image sensors, organic materials are promising candidates due to the following advantages: tunability of optoelectronic/spectral response and low-temperature low-cost processes. Here, a photolithographic process is developed to prepare a hemispherical image sensor array using organic thin film photomemory transistors with a density of 308 pixels per square centimeter. This design includes only one photomemory transistor as a single active pixel, in contrast to the conventional pixel architecture, consisting of select/readout/reset transistors and a photodiode. The organic photomemory transistor, comprising light-sensitive organic semiconductor and charge-trapping dielectric, is able to achieve a linear photoresponse (light intensity range, from 1 to 50 W m-2 ), along with a responsivity as high as 1.6 A W-1 (wavelength = 465 nm) for a dark current of 0.24 A m-2 (drain voltage = -1.5 V). These observed values represent the best responsivity for similar dark currents among all the reported hemispherical image sensor arrays to date. A transfer method was further developed that does not damage organic materials for hemispherical organic photomemory transistor arrays. These developed techniques are scalable and are amenable for other high-resolution 3D organic semiconductor devices.

Efficacy and safety of oxiracetam in patients with vascular cognitive impairment: A multicenter, randomized, double-blinded, placebo-controlled, phase IV clinical trial.

BACKGROUND: Oxiracetam may have a modest effect on preventing cognitive decline. Exercise can also enhance cognitive function. This trial aims to investigate the effect of oxiracetam on post-stroke cognitive impairment and explore whether this effect is modified by exercise. Furthermore, the mechanisms that mediate this effect will be investigated through a neural network analysis. METHODS: This is a multicenter, randomized, double-blind, placebo-controlled phase IV trial. Patients who complained of cognitive decline 3 months after stroke and had a high risk of cognitive decline were eligible. Patients were randomly assigned to receive either 800 mg of oxiracetam or placebo twice daily for 36 weeks. After randomization, a predetermined exercise protocol was provided to each participant, and the degree of physical activity was assessed using wrist actigraphy at 4, 12, 24, and 36 weeks. Resting-state functional MRI was obtained in baseline and 36-week follow-up. Co-primary endpoints are changes in the Mini-Mental State Examination and Clinical Dementia Rating-Sum of Boxes. Secondary endpoints include changes in the NINDS-CSN VCIHS-Neuropsychology Protocol, Euro QoL, patient's global assessment, and functional network connectivity. If there is a significant difference in physical activity between the two groups, the interaction effect between physical activity and the treatment group will be examined. A total of 500 patients were enrolled from February 2018, and the last patient's final follow-up was completed in September 2022. CONCLUSION: This trial is meaningful not only to prove the efficacy of oxiracetam, but also evaluate whether exercise can modify the effects of medication and how cognitive function can be restored. Trial registrationhttp://cris.nih.go.kr (KCT0005137).

Dystypia without aphasia associated with visuospatial memory impairment in a patient with acute stroke.

Keyboard typing is a multifunctional task related to language, visual-spatial and motor abilities. If one of these functions is impaired, difficulty during typing could occur. Here, a 64-year-old right-handed man is reported who developed a sudden typing disturbance without aphasia or neglect. Magnetic resonance imaging of the brain showed discrete acute infarcts in the border-zone regions, bilaterally, predominantly in the left hemisphere. The neuropsychiatric testing showed an impaired visual-spatial memory domain; however, other cognitive functions were all normal. These findings suggest that visual-spatial memory impairment, associated with a left frontal subcortical infarct, is a probable anatomic substrate associated with the inability to type.

Chip-less wireless electronic skins by remote epitaxial freestanding compound semiconductors.

Recent advances in flexible and stretchable electronics have led to a surge of electronic skin (e-skin)-based health monitoring platforms. Conventional wireless e-skins rely on rigid integrated circuit chips that compromise the overall flexibility and consume considerable power. Chip-less wireless e-skins based on inductor-capacitor resonators are limited to mechanical sensors with low sensitivities. We report a chip-less wireless e-skin based on surface acoustic wave sensors made of freestanding ultrathin single-crystalline piezoelectric gallium nitride membranes. Surface acoustic wave-based e-skin offers highly sensitive, low-power, and long-term sensing of strain, ultraviolet light, and ion concentrations in sweat. We demonstrate weeklong monitoring of pulse. These results present routes to inexpensive and versatile low-power, high-sensitivity platforms for wireless health monitoring devices.

Effect of literacy and education on the visuoconstructional ability of non-demented elderly individuals.

Learning to read and to write influences not only verbal skills but also global cognitive performance. Our study aimed to compare the visuoconstructional abilities of elderly illiterates with those of elderly literates. A total of 125 healthy subjects over 65 years old were recruited. Korean version of Mini-Mental State Examination (K-MMSE) and the Alzheimer's Disease Assessment Scale-cognitive subscale (ADAS-cog) constructional praxis examination were used. We divided subjects into three groups (educated literate n = 53, uneducated literate n = 36 and uneducated illiterate n = 36). Interlocking pentagons drawing, a part of the K-MMSE, was scored using the 6-point hierarchical scale. The uneducated-illiterate group obtained significantly lower scores than did the other two groups. Scores on the ADAS-cog constructional praxis test were highest in the educated-literate group and those in the uneducated-illiterate group obtained the lowest scores. We demonstrated that illiteracy influences not only language performance but also visuoconstructional functioning.

Reversible posterior leukoencephalopathy syndrome after cervical transforaminal epidural steroid injection presenting as transient blindness.

Transforaminal epidural steroid injections have been introduced as a nonsurgical treatment for cervical pain syndromes; however, they have also raised safety concerns. We present a patient who developed a headache and bilateral visual disturbance after cervical transforaminal epidural steroid injections. Brain magnetic resonance imaging showed a high signal intensity in the posterior region on T2-weighted and fluid-attenuated inversion recovery images, and the findings of diffusion-weighted imaging and the apparent diffusion coefficient map suggested vasogenic edema. The symptoms and abnormal imaging findings disappeared during follow-up. The clinical and imaging characteristics and their complete reversibility corresponded to reversible posterior leukoencephalopathy syndrome.

Long-term reliable physical health monitoring by sweat pore-inspired perforated electronic skins.

Electronic skins (e-skins)-electronic sensors mechanically compliant to human skin-have long been developed as an ideal electronic platform for noninvasive human health monitoring. For reliable physical health monitoring, the interface between the e-skin and human skin must be conformal and intact consistently. However, conventional e-skins cannot perfectly permeate sweat in normal day-to-day activities, resulting in degradation of the intimate interface over time and impeding stable physical sensing. Here, we present a sweat pore-inspired perforated e-skin that can effectively suppress sweat accumulation and allow inorganic sensors to obtain physical health information without malfunctioning. The auxetic dumbbell through-hole patterns in perforated e-skins lead to synergistic effects on physical properties including mechanical reliability, conformability, areal mass density, and adhesion to the skin. The perforated e-skin allows one to laminate onto the skin with consistent homeostasis, enabling multiple inorganic sensors on the skin to reliably monitor the wearer's health over a period of weeks.

The prevalence and patterns of pharyngoesophageal dysmotility in patients with early stage Parkinson's disease.

Dysphagia occurs in the majority of patients with Parkinson's disease (PD) and is known to correlate with abnormalities of oropharyngeal function. The aim of this study was to evaluate pharyngoesophageal activity in patients with early-stage PD. Newly diagnosed PD patients with a symptom duration not exceeding 3 years were included. All PD patients were questioned about symptoms of dysphagia and underwent combined multichannel intraluminal impedance manometry and multiple rapid swallow tests. Fifty-four patients (22 men and 32 women, 67.1 ± 10.3 years) were enrolled. The duration of Parkinsonian motor symptoms was 11.5 ± 8.8 months, the Hoehn and Yahr stage was 1.6 ± 0.4, and the total Unified Parkinson's Disease Rating Scale was 25.1 ± 18.6. Esophageal manometry in the liquid swallow and viscous swallow tests was abnormal in 22 (40.7%) and 31 (67.4%) patients, respectively. Although manometric abnormalities were more common in patients with more severe dysphagia symptoms, many patients with no or minimal symptoms also had manometric abnormalities. Repetitive deglutition significantly correlated with failed peristalsis and incomplete bolus transit. Abnormal responses to multiple rapid swallow tests were found in 33 out of 54 patients; 29 with incomplete inhibition (repetitive contraction) and 4 with failed peristalsis. These results suggest that the majority of patients with early-stage PD showed pharyngeal and esophageal dysfunction even before clinical manifestations of dysphagia, which may reflect selective involvement of either the brain stem or the esophageal myenteric plexus in early-stage PD.

Group-specific regional white matter abnormality revealed in diffusion tensor imaging of medial temporal lobe epilepsy without hippocampal sclerosis.

PURPOSE: In comparison to temporal lobe epilepsy (TLE) patients with hippocampal sclerosis (TLE-HS), TLE patients without HS (TLE-NH) have a similar clinical course but may result in worse surgical outcome. We investigated whether the clinical features related to the lack of HS in TLE patients (TLE-NH) can be explained by water diffusion abnormalities throughout diffusion tensor imaging (DTI) by voxel-based analysis. METHODS: Nineteen patients with TLE-HS (left/right TLE 12:7), 18 patients with TLE-NH (left/right TLE 10:8), and 20 controls were included in the study. By statistical parametric mapping (SPM2), the diffusion properties specific to disease characteristics (TLE-HS vs. TLE-NH) were analyzed. RESULTS: In TLE-HS, we found the areas of increased mean diffusivity (MD) in their ipsilateral temporal and extratemporal areas including the hippocampus, parahippocampal, and frontoparietal regions. Left TLE-HS showed a characteristic MD increase in the ipsilateral posterior cingulum, isthmus of corpus callosum, and contralateral occipital and temporal regions, which was not observed in right TLE-HS group. In left TLE-NH, two regions of increased MD were observed in the ipsilateral posterior fornix (within fusiform gyrus) and posterior cingulum. Right TLE-NH did not show any increased MD. DISCUSSION: In left TLE-NH, we could find the water diffusion change along the posterior cingulum, which was quite different from the extensive abnormality from TLE-HS. In addition, there was a lesion-side-specific distribution (left predominant) of pathology in mesial TLE. This provides a possibility that TLE-NH is a heterogeneous or entity different from TLE-HS.