Search

Silent communication based on biosignals from facial muscle requires accurate detection of its directional movement and thus optimally positioning minimum numbers of sensors for higher accuracy of speech recognition with a minimal person-to-person variation. So far, previous approaches based on electromyogram or pressure sensors are ineffective in detecting the directional movement of facial muscles. Therefore, in this study, high-performance strain sensors are used for separately detecting x- and y-axis strain. Directional strain distribution data of facial muscle is obtained by applying three-dimensional digital image correlation. Deep learning analysis is utilized for identifying optimal positions of directional strain sensors. The recognition system with four directional strain sensors conformably attached to the face shows silent vowel recognition with 85.24% accuracy and even 76.95% for completely nonobserved subjects. These results show that detection of the directional strain distribution at the optimal facial points will be the key enabling technology for highly accurate silent speech recognition.

In this study, Ca2LaNbO6:Mn4+deep red phosphors with a double-perovskite structure were synthesized under different concentrations of Mn4+ions by a traditional solid-state reaction method. These phosphor samples show deep red emission centered at 683 nm due to the 2E → 4A2transition of the Mn4+ion. The calculated corresponding Commission International de IíEclairage (CIE) coordinates of phosphor was (0.704, 0.271). When applied to near ultra violet light emitting diode (NUV LED) chips, it was confirmed that the color rendering index (CRI) value varies according to the thickness of the phosphor film, and the CRI value increases as the 393/696 nm intensity ratio approaches 1. These research results suggest that white light emitting diode (WLED) CRI can be selectively improved by controlling the thickness of phosphor film.

Conventional wearable electronics do not have conformal contact with the skin, so they might produce unreliable detecting of physiological signals during continuous health monitoring. This leads to the skin‐like healthcare patch that ensure secure contact with skin and maximizes user's comfort during daily life. Here, we present skin‐like stretchable and conformable healthcare patch in which stretchable organic light‐emitting diode (OLED) matrix display and a stretchable organic photoplethysmography (PPG) sensor are implemented together. The patch, fabricated on elastomer substrate without pre‐strained fabricating process, maintain stable operation up to 30% strain by the use of the stress relief layers and deformable micro‐cracked interconnects that reduce the mechanical stress of the OLED matrix display and PPG sensor. The simple device structure and reliable fabrication process show promise for commercialization of healthcare patch as novel form‐factor of wearable electronics.

Supplemental Digital Content is available in the text.

To rationally design and synthesize organic semiconductor materials and optimize the printing processes of semiconductor films, it is necessary to understand the charge transport behavior of inkjet-printed organic semiconductor films. Herein, the temperature and gate-bias-dependent charge transport behaviors in a polymer field-effect transistor (PFET) were studied. The PFET used a poly[(tetryldodecyloctathiophene-alt-didodecylbithiazole)-co-(tetryldodecylhexathiophene-alt-didodecylbithiazole)] (P(8T2Z-co-6T2Z)-12) polymer film formed by inkjet printing as the active channel layer. The temperature-dependent mobility curves of the PFET measured under various gate-bias conditions fit well with the multiple trap and release (MTR) model and polaron hopping transport model (PHM) at temperatures below and above 250 K, respectively. The charge transport behaviors in the inkjet-printed P(8T2Z-co-6T2Z)-12 film were revealed through a combination of the MTR model and PHM. At temperatures below 250 K, charge carriers were negligibly affected by lattice vibration and required a low activation energy to move from site to site. In contrast, at temperatures above 250 K, charge carriers gradually coupled with phonons under the influence of lattice vibration and thus required a relatively higher activation energy. The insight into charge transport obtained through this study would provide practical benefits for the development of organic electronic device design and fabrication.

Strategies to improve stretchability of polymer semiconductors, such as introducing flexible conjugation-breakers or adding flexible blocks, usually result in degraded electrical properties. In this work, we propose a concept to address this limitation, by introducing conjugated rigid fused-rings with optimized bulky side groups and maintaining a conjugated polymer backbone. Specifically, we investigated two classes of rigid fused-ring systems, namely, benzene-substituted dibenzothiopheno[6,5-b:6′,5′-f]thieno[3,2-b]thiophene (Ph-DBTTT) and indacenodithiophene (IDT) systems, and identified molecules displaying optimized electrical and mechanical properties. In the IDT system, the polymer PIDT-3T-OC12-10% showed promising electrical and mechanical properties. In fully stretchable transistors, the polymer PIDT-3T-OC12-10% showed a mobility of 0.27 cm2V–1s–1at 75% strain and maintained its mobility after being subjected to hundreds of stretching–releasing cycles at 25% strain. Our results underscore the intimate correlation between chemical structures, mechanical properties, and charge carrier mobility for polymer semiconductors. Our described molecular design approach will help to expedite the next generation of intrinsically stretchable high-performance polymer semiconductors.

Organic semiconductors (OSCs) are of interest for replacing traditional Si-based semiconductors as their flexibility and transparency enable new applications. The properties of OSC materials greatly depend on their orientation and molecular arrangement, which are strongly dependent on the underlying substrate material. Hence, in this study, in situ ultraviolet photoelectron spectroscopy (UPS) is used to elucidate the effect of the substrate on OSC orientation. Two types of OSCs, namely those with shape anisotropy (pentacene, dinaphtho[2,3-b:2′,3′-f]thieno[3,2-b]thiophene, and dibenzothiopheno[6,5-b:6′,5′-f]thieno[3,2-b]thiophene) and those with shape isotropy (N,N′-di(1-naphthyl)-N,N′-diphenyl-(1,1′-biphenyl)-4,4′-diamine, tris(4-carbazoyl-9-ylphenyl)amine, and [6,6]-phenyl C71 butyric acid methyl ester), are deposited on different electrode materials. The differences in the UPS spectra of these materials are observed directly. In general, the orientation of anisotropic OSC molecules significantly depends on the substrate properties, while that of the isotropic ones do not. All the anisotropic OSC molecules grown on poly(3,4-ethylenedioxythiophene)-polystyrenesulfonate (PEDOT:PSS) electrodes show a greater degree of molecular ordering than those grown on Au and multiwalled carbon nanotube/PEDOT:PSS electrodes. The molecular arrangements within the OSC/electrode structures are reflected in the energy-level shifts in the corresponding UPS spectra and hence in the electronic configurations. The results of this study should aid the design and synthesis of OSC materials with configurations suitable for organic electronic devices.

Supplemental Digital Content is available in the text.

Nerinetide, an eicosapeptide that interferes with post-synaptic density protein 95, is a neuroprotectant that is effective in preclinical stroke models of ischaemia-reperfusion. In this trial, we assessed the efficacy and safety of nerinetide in human ischaemia-reperfusion that occurs with rapid endovascular thrombectomy in patients who had an acute ischaemic stroke.

ObjectiveIntracranial atherosclerosis is a major cause of ischaemic stroke worldwide. A number of studies have shown the effects of statin treatment on coronary and carotid artery plaques, but there is little evidence on the effects of statin treatment on intracranial atherosclerotic plaques.MethodsThe Intensive Statin Treatment in Acute Ischaemic Stroke Patients with Intracranial Atherosclerosis - High-Resolution Magnetic Resonance Imaging (STAMINA-MRI) Trial is a single-arm, prospective, observational study monitoring imaging and clinical outcomes of high-dose statin treatment among statin-naive patients with acute ischaemic stroke caused by symptomatic intracranial atherosclerosis. The primary outcome was the change in vascular remodelling and plaque characteristics before and after 6 months (median: 179 days, IQR 163–189 days) of statin treatment measured by high-resolution MRI (HR-MRI).ResultsA total of 77 patients (mean age: 62.6±13.7 years, 61.0% women) were included in this study. Low-density lipoprotein cholesterol (LDL-C) levels (mg/dL) at initial and follow-up assessments were 125.81±35.69 and 60.95±19.28, respectively. Overall, statin treatment significantly decreased enhancement of plaque volume (mm3, 32.07±39.15 vs 17.06±34.53, p=0.013), the wall area index (7.50±4.28 vs 5.86±4.05, p=0.016) and stenosis degree (%, 76.47±20.23 vs 64.05±21.29, p<0.001), but not the remodelling index (p=0.195). However, 35% patients showed no change or increased enhancement volume and stenosis degree after statin treatment. Higher reduction of LDL-C and longer duration of statin treatment were associated with decreased enhancement volume after statin treatment.ConclusionsHigh-dose statin treatment effectively stabilised symptomatic intracranial atherosclerotic plaques as documented by HR-MRI. Further study is needed to determine laboratory and genetic factors associated with poor response to statins and alternative therapeutic options, such as proprotein convertase subtilisin-kexin type 9 inhibitors, for these patients.Trial registration numberClinicalTrials.gov NCT02458755.

Supplemental Digital Content is available in the text.

This trial, conducted according to the request of the Korean Ministry of Food and Drug Safety, investigated the potential of oxiracetam in mitigating post-stroke cognitive decline, and whether physical activity could augment its efficacy. The mechanisms behind these effects were explored using functional neuroimaging.

We report a newly synthesized donor (D)–acceptor (A)type semiconducting copolymer, consisting of thiophene as an electron-donating unit and thiazole as an electron-accepting unit (PQTBTz-TT-C8) for the active layer of the organic field-effect transistors (OFETs). Specifically, this study investigates the structure and electrical property relationships of PQTBTz-TT-C8 with comprehensive analyses on the charge-transporting properties corresponding to the spin rate of the spin coater during the formation of the PQTBTz-TT-C8 film. The crystallinity of PQTBTz-TT-C8 films is examined with grazing incidence X-ray diffraction. Temperature-dependent transfer measurements of the OFETs are conducted to extract the density of states (DOS) and characterize the charge-transport properties. Comparative analyses on charge transports within the framework of the physical model, based on polaron hopping and Gaussian DOS, reveal that the prefactors of both physical charge-transport models are independent of the spin-coating condition for the films. For staggered structural transistors, however, the thickness of the PQTBTz-TT-C8 films, which strongly affect the series resistance along the charge-transfer path in a vertical direction, is changed in accordance with the spin-coating rate. In other words, the spin-coating rate of the PQTBTz-TT-C8 films influences the thickness of the polymer films, yet any significant changes in the crystallinity of the film or electronic coupling between the neighboring molecules upon the spin-coating condition were barely noticeable. Because the PQTBTz-TT-C8 backbone chains inside the thin film are stacked up with the edge-on, the series resistances are changed according to the thickness of the film and thus the performance of the device varies depending on the thickness.

Aims Lowering the low-density lipoprotein cholesterol level reduces the risk of stroke, but it has not been clear whether the stroke risk would continuously decrease by lowering low-density lipoprotein cholesterol to a very low level. The purpose of this study was to evaluate the association between achieved low-density lipoprotein cholesterol levels and stroke risk.Methods and results A systematic search of MEDLINE, EMBASE and Cochrane Library databases was conducted to identify randomised controlled trials that tested cholesterol-lowering pharmacological therapies and reported both achieved low-density lipoprotein cholesterol levels and stroke outcomes. A meta-regression analysis was conducted to assess the linear association between the achieved low-density lipoprotein cholesterol levels and stroke risk. In addition, we evaluated pooled estimates of low-density lipoprotein cholesterol-lowering effect stratified by achieved low-density lipoprotein cholesterol levels of active arms. A total of 222,149 participants in 23 trials (52 arms of 26 studies) were included. The meta-regression analysis showed that each 1 mmol/L decrease in the achieved low-density lipoprotein cholesterol level (down to 0.78 mmol/L) was associated with a significant reduction of 23.5% (slope 0.235, 95% confidence interval 0.007–0.464, P= 0.044) in stroke risk. Irrespective of achieved low-density lipoprotein cholesterol levels in the active arms, the effects of lowering the low-density lipoprotein cholesterol level on stroke risk were significant and consistent (test for subgroup difference, P= 0.23, I2= 31%). However, there was no significant increase in haemorrhagic stroke risk with lower achieved low-density lipoprotein cholesterol levels.Conclusion In this meta-analysis of randomised controlled trials, the stroke risk monotonically reduced with lowering of low-density lipoprotein cholesterol to very low levels.

Supplemental Digital Content is available in the text.

Supplemental Digital Content is available in the text.

Background and purpose The status of collateral vessels has important clinical implications in acute ischemic stroke. To evaluate which components of ischemic symptoms were predictive of pretreatment collateral status, we tested the hypothesis that sub-item scores from the National Institutes of Health Stroke Scale (NIHSS) are associated with leptomeningeal collateral status in acute ischemic stroke with middle cerebral artery (MCA) occlusion.Methods This study included consecutive patients with acute M1 occlusion who underwent revascularization treatment for acute MCA infarction. We evaluated clinical factors and the NIHSS score according to the collateral status assessed by multiphase perfusion computed tomography.Results Eighty-six patients were included (48 good collateral status, 38 poor collateral status). The patients with poor collateral status were more likely to have a higher total NIHSS score (18 versus 11, p< 0.001) and atrial fibrillation (65.8% versus 41.7%, p= 0.026) than patients with good collateral flow. In a multiple logistic regression, the NIHSS sub-items such as profound “facial palsy” (score 2 versus 0–1) and “visual field defect” (score 2 versus 0–1) were independently associated with poor collateral status.Conclusion Among the NIHSS sub-items, severe facial palsy and visual field defect were associated with poor collateral status in acute MCA stroke with M1 occlusion. Decision on whether to treat these patients endovascularly should be made more cautiously due to the possibility of a poor outcome.

Supplemental Digital Content is available in the text.

Supplemental Digital Content is available in the text.

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.

Supplemental Digital Content is available in the text.

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.

Field-effect mobility of a polymer semiconductor film is known to be enhanced when the gate dielectric interfacing with the film is weakly polarizable. Accordingly, gate dielectrics with lower dielectric constant (k) are preferred for attaining polymer field-effect transistors (PFETs) with larger mobilities. At the same time, it is also known that inducing more charge carriers into the polymer semiconductor films helps in enhancing their field-effect mobility, because the large number of traps presented in such a disorder system can be compensated substantially. In this sense, it may seem that employing higher kdielectrics is rather beneficial because capacitance is proportional to the dielectric constant. This, however, contradicts with the statement above. In this study, we compare the impact of the two, i.e., the polarizability and the capacitance of the gate dielectric, on the transport properties of poly[(diketopyrrolopyrrole)-alt-(2,2′-(1,4-phenylene)bisthiophene)] (PDPPTPT) semiconductor layers in an FET architecture. For the study, three different dielectric layers were employed: fluorinated organic CYTOP (k= ∼2), poly(methyl methacrylate) (k= ∼4), and relaxor ferroelectric poly(vinylidene fluoride-trifluoroethylene-chlorotrifluoroethylene) (k= ∼60). The beneficial influence of attaining more carriers in the PDPPTPT films on their charge transport properties was consistently observed from all three systems. However, the more dominant factor determining the large carrier mobility was the low polarizability of the gate dielectric rather than its large capacitance; field-effect mobilities of PDPPTPT films were always larger when lower kdielectric was employed than when higher kdielectric was used. The higher mobilities obtained when using lower kdielectrics could be attributed to the suppressed distribution of the density of localized states (DOS) near the transport level and to the resulting enhanced electronic coupling between the macromolecules.

Supplemental Digital Content is available in the text.

Supplemental Digital Content is available in the text.