Synchronized wearables for the detection of haemodynamic states via electrocardiography and multispectral photoplethysmography

Cardiovascular health is typically monitored by measuring blood pressure. Here we describe a wireless on-skin system consisting of synchronized sensors for chest electrocardiography and peripheral multispectral photoplethysmography for the continuous monitoring of metrics related to vascular resistance, cardiac output and blood-pressure regulation. We used data from the sensors to train a support-vector-machine model for the classification of haemodynamic states (resulting from exposure to heat or cold, physical exercise, breath holding, performing the Valsalva manoeuvre or from vasopressor administration during post-operative hypotension) that independently affect blood pressure, cardiac output and vascular resistance. The model classified the haemodynamic states on the basis of an unseen subset of sensor data for 10 healthy individuals, 20 patients with hypertension undergoing haemodynamic stimuli and 15 patients recovering from cardiac surgery, with an average precision of 0.878 and an overall area under the receiver operating characteristic curve of 0.958. The multinodal sensor system may provide clinically actionable insights into haemodynamic states for use in the management of cardiovascular disease.

A comprehensive wireless neurological and cardiopulmonary monitoring platform for pediatrics

Neurodevelopment in the first 10 years of life is a critical time window during which milestones that define an individual's functional potential are achieved. Comprehensive multimodal neurodevelopmental monitoring is particularly crucial for socioeconomically disadvantaged, marginalized, historically underserved and underrepresented communities as well as medically underserved areas. Solutions designed for use outside the traditional clinical environment represent an opportunity for addressing such health inequalities. In this work, we present an experimental platform, ANNE EEG, which adds 16-channel cerebral activity monitoring to the existing, USA FDA-cleared ANNE wireless monitoring platform which provides continuous electrocardiography, respiratory rate, pulse oximetry, motion, and temperature measurements. The system features low-cost consumables, real-time control and streaming with widely available mobile devices, and fully wearable operation to allow a child to remain in their naturalistic environment. This multi-center pilot study successfully collected ANNE EEG recordings from 91 neonatal and pediatric patients at academic quaternary pediatric care centers and in LMIC settings. We demonstrate the practicality and feasibility to conduct electroencephalography studies with high levels of accuracy, validated via both quantitative and qualitative metrics, compared against gold standard systems. An overwhelming majority of parents surveyed during studies indicated not only an overall preference for the wireless system, but also that its use would improve their children's physical and emotional health. Our findings demonstrate the potential for the ANNE system to perform multimodal monitoring to screen for a variety of neurologic diseases that have the potential to negatively impact neurodevelopment.

Skin-Integrated Devices with Soft, Holey Architectures for Wireless Physiological Monitoring, With Applications in the Neonatal Intensive Care Unit

Continuous monitoring of vital signs is an essential aspect of operations in neonatal and pediatric intensive care units (NICUs and PICUs), of particular importance to extremely premature and/or critically ill patients. Current approaches require multiple sensors taped to the skin and connected via hard-wired interfaces to external data acquisition electronics. The adhesives can cause iatrogenic injuries to fragile, underdeveloped skin, and the wires can complicate even the most routine tasks in patient care. Here, materials strategies and design concepts are introduced that significantly improve these platforms through the use of optimized materials, open (i.e., "holey") layouts and precurved designs. These schemes 1) reduce the stresses at the skin interface, 2) facilitate release of interfacial moisture from transepidermal water loss, 3) allow visual inspection of the skin for rashes or other forms of irritation, 4) enable triggered reduction of adhesion to reduce the probability for injuries that can result from device removal. A combination of systematic benchtop testing and computational modeling identifies the essential mechanisms and key considerations. Demonstrations on adult volunteers and on a neonate in an operating NICUs illustrate a broad range of capabilities in continuous, clinical-grade monitoring of conventional vital signs, and unconventional indicators of health status.

Wireless, Skin-Interfaced Devices for Pediatric Critical Care: Application to Continuous, Noninvasive Blood Pressure Monitoring

Indwelling arterial lines, the clinical gold standard for continuous blood pressure (BP) monitoring in the pediatric intensive care unit (PICU), have significant drawbacks due to their invasive nature, ischemic risk, and impediment to natural body movement. A noninvasive, wireless, and accurate alternative would greatly improve the quality of patient care. Recently introduced classes of wireless, skin-interfaced devices offer capabilities in continuous, precise monitoring of physiologic waveforms and vital signs in pediatric and neonatal patients, but have not yet been employed for continuous tracking of systolic and diastolic BP-critical for guiding clinical decision-making in the PICU. The results presented here focus on materials and mechanics that optimize the system-level properties of these devices to enhance their reliable use in this context, achieving full compatibility with the range of body sizes, skin types, and sterilization schemes typically encountered in the PICU. Systematic analysis of the data from these devices on 23 pediatric patients, yields derived, noninvasive BP values that can be quantitatively validated against direct recordings from arterial lines. The results from this diverse cohort, including those under pharmacological protocols, suggest that wireless, skin-interfaced devices can, in certain circumstances of practical utility, accurately and continuously monitor BP in the PICU patient population.

Battery-free, wireless soft sensors for continuous multi-site measurements of pressure and temperature from patients at risk for pressure injuries

Capabilities for continuous monitoring of pressures and temperatures at critical skin interfaces can help to guide care strategies that minimize the potential for pressure injuries in hospitalized patients or in individuals confined to the bed. This paper introduces a soft, skin-mountable class of sensor system for this purpose. The design includes a pressure-responsive element based on membrane deflection and a battery-free, wireless mode of operation capable of multi-site measurements at strategic locations across the body. Such devices yield continuous, simultaneous readings of pressure and temperature in a sequential readout scheme from a pair of primary antennas mounted under the bedding and connected to a wireless reader and a multiplexer located at the bedside. Experimental evaluation of the sensor and the complete system includes benchtop measurements and numerical simulations of the key features. Clinical trials involving two hemiplegic patients and a tetraplegic patient demonstrate the feasibility, functionality and long-term stability of this technology in operating hospital settings.

Wireless sensors for continuous, multimodal measurements at the skin interface with lower limb prostheses

Precise form-fitting of prosthetic sockets is important for the comfort and well-being of persons with limb amputations. Capabilities for continuous monitoring of pressure and temperature at the skin-prosthesis interface can be valuable in the fitting process and in monitoring for the development of dangerous regions of increased pressure and temperature as limb volume changes during daily activities. Conventional pressure transducers and temperature sensors cannot provide comfortable, irritation-free measurements because of their relatively rigid construction and requirements for wired interfaces to external data acquisition hardware. Here, we introduce a millimeter-scale pressure sensor that adopts a soft, three-dimensional design that integrates into a thin, flexible battery-free, wireless platform with a built-in temperature sensor to allow operation in a noninvasive, imperceptible fashion directly at the skin-prosthesis interface. The sensor system mounts on the surface of the skin of the residual limb, in single or multiple locations of interest. A wireless reader module attached to the outside of the prosthetic socket wirelessly provides power to the sensor and wirelessly receives data from it, for continuous long-range transmission to a standard consumer electronic device such as a smartphone or tablet computer. Characterization of both the sensor and the system, together with theoretical analysis of the key responses, illustrates linear, accurate responses and the ability to address the entire range of relevant pressures and to capture skin temperature accurately, both in a continuous mode. Clinical application in two prosthesis users demonstrates the functionality and feasibility of this soft, wireless system.

Differential cardiopulmonary monitoring system for artifact-canceled physiological tracking of athletes, workers, and COVID-19 patients

Soft, skin-integrated electronic sensors can provide continuous measurements of diverse physiological parameters, with broad relevance to the future of human health care. Motion artifacts can, however, corrupt the recorded signals, particularly those associated with mechanical signatures of cardiopulmonary processes. Design strategies introduced here address this limitation through differential operation of a matched, time-synchronized pair of high-bandwidth accelerometers located on parts of the anatomy that exhibit strong spatial gradients in motion characteristics. When mounted at a location that spans the suprasternal notch and the sternal manubrium, these dual-sensing devices allow measurements of heart rate and sounds, respiratory activities, body temperature, body orientation, and activity level, along with swallowing, coughing, talking, and related processes, without sensitivity to ambient conditions during routine daily activities, vigorous exercises, intense manual labor, and even swimming. Deployments on patients with COVID-19 allow clinical-grade ambulatory monitoring of the key symptoms of the disease even during rehabilitation protocols.

A skin-conformable wireless sensor to objectively quantify symptoms of pruritus

Itch is a common clinical symptom and major driver of disease-related morbidity across a wide range of medical conditions. A substantial unmet need is for objective, accurate measurements of itch. In this article, we present a noninvasive technology to objectively quantify scratching behavior via a soft, flexible, and wireless sensor that captures the acousto-mechanic signatures of scratching from the dorsum of the hand. A machine learning algorithm validated on data collected from healthy subjects (n = 10) indicates excellent performance relative to smartwatch-based approaches. Clinical validation in a cohort of predominately pediatric patients (n = 11) with moderate to severe atopic dermatitis included 46 sleep-nights totaling 378.4 hours. The data indicate an accuracy of 99.0% (84.3% sensitivity, 99.3% specificity) against visual observation. This work suggests broad capabilities relevant to applications ranging from assessing the efficacy of drugs for conditions that cause itch to monitoring disease severity and treatment response.

Reliable, low-cost, fully integrated hydration sensors for monitoring and diagnosis of inflammatory skin diseases in any environment

Present-day dermatological diagnostic tools are expensive, time-consuming, require substantial operational expertise, and typically probe only the superficial layers of skin (~15 μm). We introduce a soft, battery-free, noninvasive, reusable skin hydration sensor (SHS) adherable to most of the body surface. The platform measures volumetric water content (up to ~1 mm in depth) and wirelessly transmits data to any near-field communication-compatible smartphone. The SHS is readily manufacturable, comprises unique powering and encapsulation strategies, and achieves high measurement precision (±5% volumetric water content) and resolution (±0.015°C skin surface temperature). Validation on n = 16 healthy/normal human participants reveals an average skin water content of ~63% across multiple body locations. Pilot studies on patients with atopic dermatitis (AD), psoriasis, urticaria, xerosis cutis, and rosacea highlight the diagnostic capability of the SHS (P _AD = 0.0034) and its ability to study impact of topical treatments on skin diseases.

Skin-interfaced soft microfluidic systems with modular and reusable electronics for in situ capacitive sensing of sweat loss, rate and conductivity

Important insights into human health can be obtained through the non-invasive collection and detailed analysis of sweat, a biofluid that contains a wide range of essential biomarkers. Skin-interfaced microfluidic platforms, characterized by soft materials and thin geometries, offer a collection of capabilities for in situ capture, storage, and analysis of sweat and its constituents. In ambulatory uses cases, the ability to provide real-time feedback on sweat loss, rate and content, without visual inspection of the device, can be important. This paper introduces a low-profile skin-interfaced system that couples disposable microfluidic sampling devices with reusable 'stick-on' electrodes and wireless readout electronics that remain isolated from the sweat. An ultra-thin capping layer on the microfluidic platform permits high-sensitivity, contactless capacitive measurements of both sweat loss and sweat conductivity. This architecture avoids the potential for corrosion of the sensing components and eliminates the need for cleaning/sterilizing the electronics, thereby resulting in a cost-effective platform that is simple to use. Optimized electrode designs follow from a combination of extensive benchtop testing, analytical calculations and FEA simulations for two sensing configurations: (1) sweat rate and loss, and (2) sweat conductivity, which contains information about electrolyte content. Both configurations couple to a flexible, wireless electronics platform that digitizes and transmits information to Bluetooth-enabled devices. On-body field testing during physical exercise validates the performance of the system in scenarios of practical relevance to human health and performance.

Skin-interfaced biosensors for advanced wireless physiological monitoring in neonatal and pediatric intensive-care units

Standard of care management in neonatal and pediatric intensive care units (NICUs and PICUs) involve continuous monitoring of vital signs with hard-wired devices that adhere to the skin and, in certain instances, include catheter-loaded pressure sensors that insert into the arteries. These protocols involve risks for complications and impediments to clinical care and skin-to-skin contact between parent and child. Here we present a wireless, non-invasive technology that not only offers measurement equivalency to these management standards but also supports a range of important additional features (without limitations or shortcomings of existing approaches), supported by data from pilot clinical studies in the neonatal intensive care unit (NICU) and pediatric ICU (PICU). The combined capabilities of these platforms extend beyond clinical quality measurements of vital signs (heart rate, respiration rate, temperature and blood oxygenation) to include novel modalities for (1) tracking movements and changes in body orientation, (2) quantifying the physiological benefits of skin-to-skin care (e.g. Kangaroo care) for neonates, (3) capturing acoustic signatures of cardiac activity by directly measuring mechanical vibrations generated through the skin on the chest, (4) recording vocal biomarkers associated with tonality and temporal characteristics of crying impervious to confounding ambient noise, and (5) monitoring a reliable surrogate for systolic blood pressure. The results have potential to significantly enhance the quality of neonatal and pediatric critical care.

Mechano-acoustic sensing of physiological processes and body motions via a soft wireless device placed at the suprasternal notch

Skin-mounted soft electronics incorporating high-bandwidth triaxial accelerometers can provide broad classes of physiologically relevant information, such as mechanoacoustic signatures of underlying body processes (such as those captured by a stethoscope) and precision kinematics of core body motions. Here, we describe a wireless device designed to be conformally placed on the suprasternal notch for the continuous measurement of mechanoacoustic signals, from subtle vibrations of the skin at accelerations of ~10⁻³ m·s⁻² to large motions of the entire body at ~10 m·s⁻², and at frequencies up to ~800 Hz. Because th measurements are a complex superposition of signals that arise from locomotion, body orientation, swallowing, respiration, cardiac activity, vocal-fold vibrations and other sources, we used frequency-domain analysis and machine learning to obtain, from human subjects during natural daily activities and exercise, real-time recordings of heart rate, respiration rate, energy intensity and other essential vital signs, as well as talking time and cadence, swallow counts and patterns, and other unconventional biomarkers. We also used the device in sleep laboratories, and validated the measurements via polysomnography.

Battery-free, wireless sensors for full-body pressure and temperature mapping

Thin, soft, skin-like sensors capable of precise, continuous measurements of physiological health have broad potential relevance to clinical health care. Use of sensors distributed over a wide area for full-body, spatiotemporal mapping of physiological processes would be a considerable advance for this field. We introduce materials, device designs, wireless power delivery and communication strategies, and overall system architectures for skin-like, battery-free sensors of temperature and pressure that can be used across the entire body. Combined experimental and theoretical investigations of the sensor operation and the modes for wireless addressing define the key features of these systems. Studies with human subjects in clinical sleep laboratories and in adjustable hospital beds demonstrate functionality of the sensors, with potential implications for monitoring of circadian cycles and mitigating risks for pressure-induced skin ulcers.

Binodal, wireless epidermal electronic systems with in-sensor analytics for neonatal intensive care

Existing vital signmonitoring systems in the neonatal intensive care unit (NICU) requiremultiple wires connected to rigid sensors with strongly adherent interfaces to the skin.We introduce a pair of ultrathin, soft, skin-like electronic devices whose coordinated, wireless operation reproduces the functionality of these traditional technologies but bypasses their intrinsic limitations.The enabling advances in engineering science include designs that support wireless, battery-free operation; real-time, in-sensor data analytics; time-synchronized, continuous data streaming; soft mechanics and gentle adhesive interfaces to the skin; and compatibility with visual inspection and with medical imaging techniques used in the NICU. Preliminary studies on neonates admitted to operating NICUs demonstrate performance comparable to the most advanced clinical-standard monitoring systems.

Relation between blood pressure and pulse wave velocity for human arteries

Continuous monitoring of blood pressure, an essential measure of health status, typically requires complex, costly, and invasive techniques that can expose patients to risks of complications. Continuous, cuffless, and noninvasive blood pressure monitoring methods that correlate measured pulse wave velocity (PWV) to the blood pressure via the Moens-Korteweg (MK) and Hughes Equations, offer promising alternatives. The MK Equation, however, involves two assumptions that do not hold for human arteries, and the Hughes Equation is empirical, without any theoretical basis. The results presented here establish a relation between the blood pressure P and PWV that does not rely on the Hughes Equation nor on the assumptions used in the MK Equation. This relation degenerates to the MK Equation under extremely low blood pressures, and it accurately captures the results of in vitro experiments using artificial blood vessels at comparatively high pressures. For human arteries, which are well characterized by the Fung hyperelastic model, a simple formula between P and PWV is established within the range of human blood pressures. This formula is validated by literature data as well as by experiments on human subjects, with applicability in the determination of blood pressure from PWV in continuous, cuffless, and noninvasive blood pressure monitoring systems.

Self-assembled three dimensional network designs for soft electronics

Low modulus, compliant systems of sensors, circuits and radios designed to intimately interface with the soft tissues of the human body are of growing interest, due to their emerging applications in continuous, clinical-quality health monitors and advanced, bioelectronic therapeutics. Although recent research establishes various materials and mechanics concepts for such technologies, all existing approaches involve simple, two-dimensional (2D) layouts in the constituent micro-components and interconnects. Here we introduce concepts in three-dimensional (3D) architectures that bypass important engineering constraints and performance limitations set by traditional, 2D designs. Specifically, open-mesh, 3D interconnect networks of helical microcoils formed by deterministic compressive buckling establish the basis for systems that can offer exceptional low modulus, elastic mechanics, in compact geometries, with active components and sophisticated levels of functionality. Coupled mechanical and electrical design approaches enable layout optimization, assembly processes and encapsulation schemes to yield 3D configurations that satisfy requirements in demanding, complex systems, such as wireless, skin-compatible electronic sensors.

Many low modulus systems, such as sensors, circuits and radios, are in 2D formats that interface with soft human tissue in order to form health monitors or bioelectronic therapeutics. Here the authors produce 3D architectures, which bypass engineering constraints and performance limitations experienced by their 2D counterparts.

Soft Elastomers with Ionic Liquid-Filled Cavities as Strain Isolating Substrates for Wearable Electronics

Managing the mechanical mismatch between hard semiconductor components and soft biological tissues represents a key challenge in the development of advanced forms of wearable electronic devices. An ultralow modulus material or a liquid that surrounds the electronics and resides in a thin elastomeric shell provides a strain-isolation effect that enhances not only the wearability but also the range of stretchability in suitably designed devices. The results presented here build on these concepts by (1) replacing traditional liquids explored in the past, which have some nonnegligible vapor pressure and finite permeability through the encapsulating elastomers, with ionic liquids to eliminate any possibility for leakage or evaporation, and (2) positioning the liquid between the electronics and the skin, within an enclosed, elastomeric microfluidic space, but not in direct contact with the active elements of the system, to avoid any negative consequences on electronic performance. Combined experimental and theoretical results establish the strain-isolating effects of this system, and the considerations that dictate mechanical collapse of the fluid-filled cavity. Examples in skin-mounted wearable include wireless sensors for measuring temperature and wired systems for recording mechano-acoustic responses.

Ultraminiaturized photovoltaic and radio frequency powered optoelectronic systems for wireless optogenetics

OBJECTIVE

Wireless control and power harvesting systems that operate injectable, cellular-scale optoelectronic components provide important demonstrated capabilities in neuromodulatory techniques such as optogenetics. Here, we report a radio frequency (RF) control/harvesting device that offers dramatically reduced size, decreased weight and improved efficiency compared to previously reported technologies. Combined use of this platform with ultrathin, multijunction, high efficiency solar cells allows for hundred-fold reduction of transmitted RF power, which greatly enhances the wireless coverage.

APPROACH

Fabrication involves separate construction of the harvester and the injectable µ-ILEDs. To test whether the presence of the implantable device alters behavior, we implanted one group of wild type mice and compared sociability behavior to unaltered controls. Social interaction experiments followed protocols defined by Silverman et al. with minor modifications.

MAIN RESULTS

The results presented here demonstrate that miniaturized RF harvesters, and RF control strategies with photovoltaic harvesters can, when combined with injectable µ-ILEDs, offer versatile capabilities in optogenetics. Experimental and modeling studies establish a range of effective operating conditions for these two approaches. Optogenetics studies with social groups of mice demonstrate the utility of these systems.

SIGNIFICANCE

The addition of miniaturized, high performance photovoltaic cells significantly expands the operating range and reduces the required RF power. The platform can offer capabilities to modulate signaling path in the brain region of freely-behaving animals. These suggest its potential for widespread use in neuroscience.

Water-soluble thin film transistors and circuits based on amorphous indium-gallium-zinc oxide

This paper presents device designs, circuit demonstrations, and dissolution kinetics for amorphous indium-gallium-zinc oxide (a-IGZO) thin film transistors (TFTs) comprised completely of water-soluble materials, including SiNx, SiOx, molybdenum, and poly(vinyl alcohol) (PVA). Collections of these types of physically transient a-IGZO TFTs and 5-stage ring oscillators (ROs), constructed with them, show field effect mobilities (∼10 cm2/Vs), on/off ratios (∼2×10(6)), subthreshold slopes (∼220 mV/dec), Ohmic contact properties, and oscillation frequency of 5.67 kHz at supply voltages of 19 V, all comparable to otherwise similar devices constructed in conventional ways with standard, nontransient materials. Studies of dissolution kinetics for a-IGZO films in deionized water, bovine serum, and phosphate buffer saline solution provide data of relevance for the potential use of these materials and this technology in temporary biomedical implants.

Soft network composite materials with deterministic and bio-inspired designs

Hard and soft structural composites found in biology provide inspiration for the design of advanced synthetic materials. Many examples of bio-inspired hard materials can be found in the literature; far less attention has been devoted to soft systems. Here we introduce deterministic routes to low-modulus thin film materials with stress/strain responses that can be tailored precisely to match the non-linear properties of biological tissues, with application opportunities that range from soft biomedical devices to constructs for tissue engineering. The approach combines a low-modulus matrix with an open, stretchable network as a structural reinforcement that can yield classes of composites with a wide range of desired mechanical responses, including anisotropic, spatially heterogeneous, hierarchical and self-similar designs. Demonstrative application examples in thin, skin-mounted electrophysiological sensors with mechanics precisely matched to the human epidermis and in soft, hydrogel-based vehicles for triggered drug release suggest their broad potential uses in biomedical devices.

Rugged and breathable forms of stretchable electronics with adherent composite substrates for transcutaneous monitoring

Research in stretchable electronics involves fundamental scientific topics relevant to applications with importance in human healthcare. Despite significant progress in active components, routes to mechanically robust construction are lacking. Here, we introduce materials and composite designs for thin, breathable, soft electronics that can adhere strongly to the skin, with the ability to be applied and removed hundreds of times without damaging the devices or the skin, even in regions with substantial topography and coverage of hair. The approach combines thin, ultralow modulus, cellular silicone materials with elastic, strain-limiting fabrics, to yield a compliant but rugged platform for stretchable electronics. Theoretical and experimental studies highlight the mechanics of adhesion and elastic deformation. Demonstrations include cutaneous optical, electrical and radio frequency sensors for measuring hydration state, electrophysiological activity, pulse and cerebral oximetry. Multipoint monitoring of a subject in an advanced driving simulator provides a practical example.

Using nanoscale thermocapillary flows to create arrays of purely semiconducting single-walled carbon nanotubes

Among the remarkable variety of semiconducting nanomaterials that have been discovered over the past two decades, single-walled carbon nanotubes remain uniquely well suited for applications in high-performance electronics, sensors and other technologies. The most advanced opportunities demand the ability to form perfectly aligned, horizontal arrays of purely semiconducting, chemically pristine carbon nanotubes. Here, we present strategies that offer this capability. Nanoscale thermocapillary flows in thin-film organic coatings followed by reactive ion etching serve as highly efficient means for selectively removing metallic carbon nanotubes from electronically heterogeneous aligned arrays grown on quartz substrates. The low temperatures and unusual physics associated with this process enable robust, scalable operation, with clear potential for practical use. We carry out detailed experimental and theoretical studies to reveal all of the essential attributes of the underlying thermophysical phenomena. We demonstrate use of the purified arrays in transistors that achieve mobilities exceeding 1,000 cm(2) V(-1) s(-1) and on/off switching ratios of ∼10,000 with current outputs in the milliamp range. Simple logic gates built using such devices represent the first steps toward integration into more complex circuits.

Electrostatic dimension of aligned-array carbon nanotube field-effect transistors

Accurate electrostatics modeling of nanotubes (NTs)/nanowires (NWs) has significant implications for the ultimate scalability of aligned-array NT/NW field-effect transistors (FETs). The analysis to date has focused on limits of capacitive coupling between the 1D channel and 2D gate that is strictly relevant only in the linear response operation of NT/NW-FETs. Moreover, the techniques of electrostatic doping by independent gates that cover only part of the channel are widely used, but the nature of its electrostatic coupling has not been explored. In this paper, we use a three-dimensional, self-consistent model for NT/NW-FETs to interpret the essence of electrostatic coupling with complex configuration of electrode geometries. The interplay between 3D electric fields and its 1D termination onto the NTs/NWs suggests surprising complexity of electrostatic interaction not captured in simpler models. This coupling can change the performance metrics such as ON and OFF currents by orders of magnitude depending on (1) NT/NW density, (2) bias voltage, and (3) gate overlap length. Remarkably, this parasitic coupling persists regardless of the gate oxide thickness, changes in dielectric constant, and/or the width of the diameter distribution of NTs/NWs. The predictions of the model are systematically validated by a series of experiments.

Acute herpetic esophagitis--a case report

We report a case of acute herpetic esophagitis in a 33 year old man who was presumed to be immuno-compromised following prolonged steroid and cyclosporin treatment for acute rejection of a transplanted kidney. In Korea, all reported cases of herpetic esophagitis have been diagnosed in immuno-compromised and debilitated patients with a typical endoscopic appearance of ulcerating lesions. However, our patient showed multiple vesicular lesions without ulcer along the entire esophagus. The diagnosis was confirmed by colorimetric detection of herpes virus DNA using in situ hybridization. The endoscopic findings reported herein probably represent the typical early stage of acute herpetic esophagitis.