Ultra-Low Power Wearable Infant Sleep Position Sensor.

Numerous wearable sensors have been developed for a variety of needs in medical/healthcare/wellness/sports applications, but there are still doubts about their usefulness due to uncomfortable fit or frequent battery charging. Because the size or capacity of battery is the major factor affecting the convenience of wearable sensors, power consumption must be reduced. We developed a method that can significantly reduce the power consumption by introducing a signal repeater and a special switch that provides power only when needed. Antenna radiation characteristics are an important factor in wireless wearable sensors, but soft material encapsulation for comfortable fit results in poor wireless performance. We improved the antenna radiation characteristics by a local encapsulation patterning. In particular, ultra-low power operation enables the use of paper battery to achieve a very thin and flexible form factor. Also, we verified the human body safety through specific absorption rate simulations. With these methods, we demonstrated a wearable infant sleep position sensor. Infants are unable to call for help in unsafe situations, and it is not easy for caregivers to observe them all the time. Our wearable sensor detects infants' sleep positions in real time and automatically alerts the caregivers when needed.

Intrauterine Growth Restriction Affects Cerebellar Granule Cells in the Developing Guinea Pig Brain.

Intrauterine growth restriction (IUGR) can lead to adverse neurodevelopmental sequelae in postnatal life. However, the effects of IUGR on the cerebellum are still to be fully elucidated. A major determinant of growth and development of the cerebellum is proliferation and subsequent migration of cerebellar granule cells. Our objective was to determine whether IUGR, induced by chronic placental insufficiency (CPI) in guinea pigs, results in abnormal cerebellar development due to deficits suggestive of impaired granule cell proliferation and/or migration. CPI was induced by unilateral ligation of the uterine artery at mid-gestation, producing growth-restricted (GR) foetuses at 52 and 60 days of gestation (dg), and neonates at 1 week postnatal age (term approx. 67 dg). Controls were from sham-operated animals. In GR foetuses compared with controls at 52 dg, the external granular layer (EGL) width and internal granular layer (IGL) area were similar. In GR foetuses compared with controls at 60 dg: (a) the EGL width was greater (p < 0.005); (b) the IGL area was smaller (p < 0.005); (c) the density of Ki67-negative (postmitotic) granule cells in the EGL was greater (p < 0.01); (d) the somal area of Purkinje cells was reduced (p < 0.005), and (e) the linear density of Bergmann glia was similar. The EGL width in GR foetuses at 60 dg was comparable to that of 52 dg control and GR foetuses. The pattern of p27-immunoreactivity in the EGL was the inverse of Ki67-immunoreactivity at both foetal ages; there was no difference between control and GR foetuses at either age in the width of p27-immunoreactivity, or in the percentage of the EGL width that it occupied. In the molecular layer of GR neonates compared with controls there was an increase in the areal density of granule cells (p < 0.05) and in the percentage of migrating to total number of granule cells (p < 0.01) at 1 week but not at 60 dg (p > 0.05). Thus, we found no specific evidence that IUGR affects granule cell proliferation, but it alters the normal program of migration to the IGL and, in addition, the development of Purkinje cells. Such alterations will likely affect the development of appropriate circuitry and have implications for cerebellar function.

The effect of diet control on puberty onset and immunoreactivity of kisspeptin and neurokinin B in female rats.

Early onset puberty and irregular estrous cycles occur more frequently in rats which are fed a high-fat diet. Kisspeptin is an essential factor for the regulation of sexual maturation and is co-expressed with neurokinin B in neurons in the hypothalamic arcuate nucleus. However, the effects of a diet change on kisspeptin neuronal signaling are not well-understood. Therefore, in this study, we examined the immunoreactivity pattern of the kisspeptin/kiss1-receptor (KISS1R) and neurokinin B/neurokinin3-receptor (R). Pups born to high-fat diet rats were exposed to a high-fat diet until the onset of puberty. From puberty, the offspring originally exposed to a high-fat diet were fed a normal diet up to 85 postnatal days (PND 85). We examined kisspeptin/Kiss1-receptor and neurokinin B/neurokinin3-receptor immunoreactivity (IR) in the arcuate nucleus of the pups. The onset of puberty in the high-fat group was significantly earlier than the control group. At the onset of puberty, the densities of kisspeptin and neurokinin B IR cells were significantly higher in the high-fat diet group than in the control group; however, the densities of KISS1 and neurokinin 3-receptor IR cells did not differ between the two groups. At PND 85, the density of kisspeptin and neurokinin B IR cells did not differ between control and high fat group. The density of densities of KISS1 and neurokinin 3-receptor IR cells also did not differ between groups at this stage. These data suggest that a high-fat diet can influence puberty onset and the immunoreactivity of kisspeptin and neurokinin B. These effects can be modified by dietary control.

Dexmedetomidine Stereotaxic Injection Alleviates Neuronal Loss Following Bilateral Common Carotid Artery Occlusion via Up-Regulation of BDNF Expression.

BACKGROUND/AIM: Neurogenesis is an important process in the recovery from neurological damage caused by ischemic lesions. Endogenous neurogenesis is insufficient to restore neuronal damage following cerebral ischemia. Dexmedetomidine (DEX) exerts neuroprotective effects against cerebral ischemia and ischemia/reperfusion injury. DEX promotes neurogenesis, including neuronal proliferation and maturation in the hippocampus. In a previous study, we showed that early neurogenesis increased 3 days after bilateral common carotid artery occlusion (BCCAO). In this study, we investigated the effect of DEX on neurogenesis 3 days after BCCAO. MATERIALS AND METHODS: Male Sprague-Dawley (SD) rats (7-8 weeks old) were used as a BCCAO model. Right and left common carotid arteries of the rats were occluded using 4-0 silk sutures. Two hours after surgery, an intracranial DEX injection was administered to rats that underwent surgery using a stereotaxic injector. Brains were obtained from control and BCCAO rats 3 days after surgery. Immunohistochemistry was performed on the cortex and dentate gyrus of the hippocampus using a NeuN antibody. Western blot was performed with HIF1α and brain-derived neurotrophic factor (BDNF) antibodies. RESULTS: The number of mature neurons decreased 3 days after BCCAO, but DEX treatment alleviated neural loss in the parietal cortex and hippocampus. Up-regulation of BDNF was also observed after dexmedetomidine treatment. CONCLUSION: Stereotaxic injection of dexmedetomidine alleviates neural loss following BCCAO by up-regulating BDNF expression.

Controlling electric dipoles in nanodielectrics and its applications for enabling air-stable n-channel organic transistors.

We present a new method to manipulate the channel charge density of field-effect transistors using dipole-generating self-assembled monolayers (SAMs) with different anchor groups. Our approach maintains an ideal interface between the dipole layers and the semiconductor while changing the built-in electric potential by 0.41-0.50 V. This potential difference can be used to change effectively the electrical properties of nanoelectronic devices. We further demonstrate the application of the SAM dipoles to enable air-stable operation of n-channel organic transistors.

Ultra-Low-Power Wearable Vibration Sensor with Highly Accurate Embedded Classifier.

Reducing the power consumption of wearable sensors is a very important issue in relation to the device usage time and form factor. However, continuous wireless communication to analyze the measured signal in real-time significantly increases the power consumption of the wearable sensor. In this study, we propose a wearable vibration sensor that operates with extremely low power through an embedded signal classifier, which exhibits high accuracy and low calculation load. We demonstrate cough detection through the proposed sensor system. The result exhibits an accuracy of 93.0%, which is 24.3% higher than the conventional embedded classification algorithm. Also, the proposed approach reduces the average power consumption of the wearable sensor by 8.8 times. Clinical Relevance-People can measure the vibration from the body using an ultra-low-power wearable sensor. It provides a solution to automatically monitor cough symptoms in numerous patients.

Study on Optimal Position and Covering Pressure of Wearable Neck Microphone for Continuous Voice Monitoring.

Vocal cord disorder is one of the important health problems, especially in noisy industrial sites where excessive voice is required. A convenient and reliable communication method is required in a noisy environment to prevent the related disorders. However, the signal sensitivity of previous neck microphones is still insufficient to accurately convey the voice. In this study, we developed a skin-attachable neck microphone with a lightweight and flexible form factor. Also, we optimized the attachment position and covering pressure to maximize the signal sensitivity. As a result, we obtained the optimal position near the thyroid cartilage and confirmed that the signal sensitivity is the highest when the covering pressure is approximately 4 mmHg.Clinical Relevance- People can measure the voice status using a wearable neck microphone at the optimal position and covering pressure. It provides a solution to keep the vocal cords in good health even in a noisy environment.

A Wearable System for Heart Rate Recovery Evaluation with Real-Time Classification on Exercise Condition.

Heart rate recovery (HRR) is a convenient index to assess a cardiovascular autonomic function response to physical exercise. HRR monitoring during daily exercise can be an effective way to verify cardiorespiratory performance. Because HRR varies depending on exercise intensity and resting condition, an exercise condition needs to be acquired for a reliable HRR analysis. This study presents a wearable system for HRR evaluation with automatic labeling of exercise conditions using real-time activity classification. We developed an activity classification algorithm using two features from accelerometer sensor: an acceleration peak and an angle tilt peak. The classification algorithm was applied to a chest-attached wearable device with an embedded electrocardiogram sensor and accelerometer sensors. We classified daily activities such as running, walking, and postural transitions performed under supervised conditions. The wearable device system accurately detected activities with a sensitivity of 99.2 % and posture transitions with a sensitivity of 92 % and specificity of 93.3 % for seven healthy subjects. The proposed wearable system can help monitor HRR during exercise training by labeling the exercise condition simultaneously.

Quantitative Muscle Fatigue Estimation with High SNR Flexible Skin Electrode.

In recent years, surface electromyography (sEMG) has been commonly used to diagnose neuromuscular abnormalities. Since sEMG measures electrical signals from various tangled muscle nerves, a high signal-to-noise ratio (SNR) is required to estimate the condition accurately. Previously, Ag/AgCl electrodes were widely used for sEMG measurements, but noble metals are more advantageous for long-term and continuous measurement. In this study, we improved the SNR of bioelectrical signals by increasing the surface area of a flexible skin-electrode made of noble metal. The electrode surface area was increased by 1.38 times with electroplating, and the SNR of sEMG was improved by 1.63 times. Utilizing the sEMG signals with high SNR, we propose a new muscle fatigue estimation algorithm for monitoring the muscle condition in real-time.

Multilayer Substrate to Use Brittle Materials in Flexible Electronics.

Flexible materials with sufficient mechanical endurance under bending or folding is essential for flexible electronic devices. Conventional rigid materials such as metals and ceramics are mostly brittle so that their properties can deteriorate under a certain amount of strain. In order to utilize high-performance, but brittle conventional materials in flexible electronics, we propose a novel flexible substrate structure with a low-modulus interlayer. The low-modulus interlayer reduces the surface strain, where active electronic components are placed. The bending results with indium tin oxide (ITO) show that a critical bending radius, where the conductivity starts to deteriorate, can be reduced by more than 80% by utilizing the low-modulus layer. We demonstrate that even rigid electrodes can be used in flexible devices by manipulating the structure of flexible substrate.

Hypoxia of Rats Subjected to Carotid Artery Ligation Results in Impaired Neurogenesis and Reduced Number of Cortical Neurons.

BACKGROUND/AIM: Cerebral ischemia is a major cause of abnormal brain development. In a cerebral ischemia model, periventricular leukomalacia (PVL), white matter lesion and a decrease in the number of subcortical neurons were observed. The aim of this study was to investigate the effect of hypoxia on neurogenesis and cell survival. MATERIALS AND METHODS: In seven-day postnatal rats, the right carotid artery was ligated. The rats were incubated either in a regular normoxic chamber (control group) or in a hypoxic chamber (PVL group, 8% 02 and 92% N2 at 37°C) for 2 h. Nestin- and NeuN-positive neurons were detected by immunohistochemistry. RESULTS: The densities of nestin-immunoreactivity (IR) cells in the cerebral parietal cortex and subventricular zone were increased with hypoxia. NeuN-IR cells in the cerebral cortex were significantly decreased in the PVL group. CONCLUSION: Perinatal white matter injury induced neurogenesis, while the survival of neurons was decreased in the cerebral cortex.

An ultrathin conformable vibration-responsive electronic skin for quantitative vocal recognition.

Flexible and skin-attachable vibration sensors have been studied for use as wearable voice-recognition electronics. However, the development of vibration sensors to recognize the human voice accurately with a flat frequency response, a high sensitivity, and a flexible/conformable form factor has proved a major challenge. Here, we present an ultrathin, conformable, and vibration-responsive electronic skin that detects skin acceleration, which is highly and linearly correlated with voice pressure. This device consists of a crosslinked ultrathin polymer film and a hole-patterned diaphragm structure, and senses voices quantitatively with an outstanding sensitivity of 5.5 V Pa-1 over the voice frequency range. Moreover, this ultrathin device (<5 µm) exhibits superior skin conformity, which enables exact voice recognition because it eliminates vibrational distortion on rough and curved skin surfaces. Our device is suitable for several promising voice-recognition applications, such as security authentication, remote control systems and vocal healthcare.

Regional Immunoreactivity of Pax6 in the Neurogenic Zone After Chronic Prenatal Hypoxia.

BACKGROUND/AIM: Neurogenesis is a complex process to generate new neurons from neural progenitor cells. Neural progenitor cells are observed in two principal neurogenic regions of the forebrain, the subventricular zone and the subgranular zone of the hippocampal dentate gyrus. The cerebral cortex also plays a role as the neurogenic zone under hypoxic conditions. Hypoxia has many effects on neurogenesis, but the effect of chronic prenatal hypoxia on paired box 6 (Pax6), a protein that plays an important role in neurogenesis, has not been studied in vivo. In the present study, we used a rat model to evaluate the effect of hypoxia on Pax6 immunoreactivity. MATERIALS AND METHODS: Hypoxia status was induced by unilateral uterine-artery ligation in pregnant rats. The fetuses were obtained from the uterine horn on the twenty-first day of pregnancy and immunohistochemistry of the fetal brain was examined regarding anti-hypoxia-induced factor 1α and Pax6 antibody. RESULTS: The density of HIF1α-IR cells in the hypoxia group was greater than the density of HIF1α-IR cells in the control group in the subventricular zone, subgranular zone, and cerebral cortex. The density of Pax6-IR cells in the hypoxic group was higher in both the subventricular zone and the subgranular zone than in the control group. However, the density of Pax6-IR cells in the cerebral cortex was lower in fetuses that experienced hypoxia than in control fetuses. CONCLUSION: These results suggest that Pax6 immunoreactivity showed diverse patterns in the neurogenic zone after prenatal hypoxia and Pax6 has important effects on neurogenesis.

The Immunoreactivity of PI3K/AKT Pathway After Prenatal Hypoxic Damage.

BACKGROUND/AIM: There is no consensus on the effect of hypoxia on neurogenesis. In this study, we investigated the immunoreactivity of BDNF and PI3K/Akt signaling after uterine artery ligation in pregnant rats. MATERIALS AND METHODS: Unilateral uterine artery ligation was performed at 16 days of gestation (dg). Fetuses from one horn with ligated artery were allocated to the hypoxic group. Immunohistochemistry was performed with primary antibodies; NeuN, BDNF, PI3K, Akt and phospho-Akt (pAkt). RESULTS: The densities of NeuN- and BDNF-immunoreactive (IR) cells in the cerebral cortex were lower in the hypoxic fetuses than in the controls at 21 dg. The density of PI3K and pAkt-IR cells in the cortex of the hypoxic group significantly decreased. The results in dentate gyrus were similar to the results in the cerebral cortex. CONCLUSION: Prenatal hypoxia reduced Akt phosphorylation, which affected neuronal survival in the cortex and dentate gyrus.

X-gal inhibits the swarming of Vibrio species.

The expressional levels of genes in swarmer cells can be determined by a simple method using X-gal-containing semisolid agars and lacZ-fusion transcription reporter strains of the genes concerned. However, X-gal alone inhibited the swarming of Vibrio, regardless of their ability to digest X-gal. Moreover, X-gal inhibited the growth of V. vulnificus containing functional lacZ. These effects of X-gal itself should be carefully considered when trying to determine the expression levels of genes in swarming cells using X-gal-containing semisolid agar.

Linearly and Highly Pressure-Sensitive Electronic Skin Based on a Bioinspired Hierarchical Structural Array.

Pressure-sensitive electronic skin composed of a hierarchical structural array exhibits outstanding linear and high sensitivity in the pressure range exerted by gentle touch. By virtue of monolayer graphene acting as electrode material, this device can be operated with low voltage. Especially, its high transparency enables an accurate placement of the device on the target position when it is used for health monitoring.

Immunoreactivity of neurogenic factor in the guinea pig brain after prenatal hypoxia.

Chronic prenatal hypoxia is considered to cause perinatal brain injury. It can result in neurological disorders such as cerebral palsy or learning disabilities. These neurological problems are related to chronic placental insufficiency (CPI), which leads to chronic hypoxemia and hypoglycemia. The effects of hypoxia on neurogenesis during development have been a matter of controversy. We therefore investigated the effect of chronic prenatal hypoxia in the brain of the fetal guinea pig using the guinea pig CPI model. Chronic placental insufficiency was induced by unilateral uterine artery ligation at 30-32 days of gestation (dg: with term defined as ∼67dg). At 50 and 60dg, fetuses were sacrificed and assigned to either the growth-restricted (GR) or control (no ligation) group. Immunohistochemistry was performed with HIF-1α, PCNA, NeuN and BDNF antibodies in the cerebral cortex and dentate gyrus. The number of NeuN-IR and BDNF-IR cells was lesser in GR fetuses than in controls in the cerebral cortex and dentate gyrus at 60dg (p<0.05). The growth of the developing brain is dependent upon the availability of growth factors such as BDNF. The reduction in the number of neuronal cells observed in our GR group was associated with the observed reduction in BDNF protein found at 60dg. There was no significant difference between control and GR fetuses in the densities of PCNA-IR cells in the subventricular zone and subgranular zone at 50 and 60dg. These findings suggest that the survival of neurons in the cerebral cortex is decreased by chronic prenatal hypoxia at 60dg.

Ubiquitous Graphene Electronics on Scotch Tape.

We report a novel concept of graphene transistors on Scotch tape for use in ubiquitous electronic systems. Unlike common plastic substrates such as polyimide and polyethylene terephthalate, the Scotch tape substrate is easily attached onto various objects such as banknotes, curved surfaces, and human skin, which implies potential applications wherein electronics can be placed in any desired position. Furthermore, the soft Scotch tape serves as an attractive substrate for flexible/foldable electronics that can be significantly bent, or even crumpled. We found that the adhesive layer of the tape with a relatively low shear modulus relaxes the strain when subjected to bending. The capacitance of the gate dielectric made of oxidized aluminum oxide was 1.5 µF cm(-2), so that a supply voltage of only 2.5 V was sufficient to operate the devices. As-fabricated graphene transistors on Scotch tape exhibited high electron mobility of 1326 (±155) cm(2) V(-1) s(-1); the transistors still showed high mobility of 1254 (±478) cm(2) V(-1) s(-1) even after they were crumpled.

Water-free transfer method for CVD-grown graphene and its application to flexible air-stable graphene transistors.

Transferring graphene without water enables water-sensitive substrates to be used in graphene electronics. A polymeric bilayer (PMMA/PBU) is coated on graphene as a supporting layer for the water-free transfer process and as an excellent passivation layer that enhances device operation.

Enhancing 2D growth of organic semiconductor thin films with macroporous structures via a small-molecule heterointerface.

The physical structure of an organic solid is strongly affected by the surface of the underlying substrate. Controlling this interface is an important issue to improve device performance in the organic electronics community. Here we report an approach that utilizes an organic heterointerface to improve the crystallinity and control the morphology of an organic thin film. Pentacene is used as an active layer above, and m-bis(triphenylsilyl)benzene is used as the bottom layer. Sequential evaporations of these materials result in extraordinary morphology with far fewer grain boundaries and myriad nanometre-sized pores. These peculiar structures are formed by difference in molecular interactions between the organic layers and the substrate surface. The pentacene film exhibits high mobility up to 6.3 cm(2) V(-1) s(-1), and the pore-rich structure improves the sensitivity of organic-transistor-based chemical sensors. Our approach opens a new way for the fabrication of nanostructured semiconducting layers towards high-performance organic electronics.