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1.
Proc Natl Acad Sci U S A ; 118(43)2021 Oct 26.
Artigo em Inglês | MEDLINE | ID: mdl-34663725

RESUMO

Early identification of atypical infant movement behaviors consistent with underlying neuromotor pathologies can expedite timely enrollment in therapeutic interventions that exploit inherent neuroplasticity to promote recovery. Traditional neuromotor assessments rely on qualitative evaluations performed by specially trained personnel, mostly available in tertiary medical centers or specialized facilities. Such approaches are high in cost, require geographic proximity to advanced healthcare resources, and yield mostly qualitative insight. This paper introduces a simple, low-cost alternative in the form of a technology customized for quantitatively capturing continuous, full-body kinematics of infants during free living conditions at home or in clinical settings while simultaneously recording essential vital signs data. The system consists of a wireless network of small, flexible inertial sensors placed at strategic locations across the body and operated in a wide-bandwidth and time-synchronized fashion. The data serve as the basis for reconstructing three-dimensional motions in avatar form without the need for video recordings and associated privacy concerns, for remote visual assessments by experts. These quantitative measurements can also be presented in graphical format and analyzed with machine-learning techniques, with potential to automate and systematize traditional motor assessments. Clinical implementations with infants at low and at elevated risks for atypical neuromotor development illustrates application of this system in quantitative and semiquantitative assessments of patterns of gross motor skills, along with body temperature, heart rate, and respiratory rate, from long-term and follow-up measurements over a 3-mo period following birth. The engineering aspects are compatible for scaled deployment, with the potential to improve health outcomes for children worldwide via early, pragmatic detection methods.

2.
Adv Mater ; : e2103974, 2021 Sep 12.
Artigo em Inglês | MEDLINE | ID: mdl-34510572

RESUMO

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.

3.
Adv Mater ; 33(39): e2103857, 2021 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-34369002

RESUMO

Wireless, skin-integrated devices for continuous, clinical-quality monitoring of vital signs have the potential to greatly improve the care of patients in neonatal and pediatric intensive-care units. These same technologies can also be used in the home, across a broad spectrum of ages, from beginning to end of life. Although miniaturized forms of such devices minimize patient burden and improve compliance, they represent life-threatening choking hazards for infants. A materials strategy is presented here to address this concern. Specifically, composite materials are introduced as soft encapsulating layers and gentle adhesives that release chemical compounds designed to elicit an intense bitter taste when placed in the mouth. Reflexive reactions to this sensation strongly reduce the potential for ingestion, as a safety feature. The materials systems described involve a non-toxic bitterant (denatonium benzoate) as a dopant in an elastomeric (poly(dimethylsiloxane)) or hydrogel matrix. Experimental and computational studies of these composite materials and the kinetics of release of the bitterant define the key properties. Incorporation into various wireless skin-integrated sensors demonstrates their utility in functional systems. This simple strategy offers valuable protective capabilities, with broad practical relevance to the welfare of children monitored with wearable devices.

4.
J Reconstr Microsurg ; 2021 Aug 17.
Artigo em Inglês | MEDLINE | ID: mdl-34404105

RESUMO

BACKGROUND: Current near-infrared spectroscopy (NIRS)-based systems for continuous flap monitoring are highly sensitive for detecting malperfusion. However, the clinical utility and user experience are limited by the wired connection between the sensor and bedside console. This wire leads to instability of the flap-sensor interface and may cause false alarms. METHODS: We present a novel wearable wireless NIRS sensor for continuous fasciocutaneous free flap monitoring. This waterproof silicone-encapsulated Bluetooth-enabled device contains two light-emitting diodes and two photodetectors in addition to a battery sufficient for 5 days of uninterrupted function. This novel device was compared with a ViOptix T.Ox monitor in a porcine rectus abdominus myocutaneous flap model of arterial and venous occlusions. RESULTS: Devices were tested in four flaps using three animals. Both devices produced very similar tissue oxygen saturation (StO2) tracings throughout the vascular clamping events, with obvious and parallel changes occurring on arterial clamping, arterial release, venous clamping, and venous release. Small interdevice variations in absolute StO2 value readings and magnitude of change were observed. The normalized cross-correlation at zero lag describing correspondence between the novel NIRS and T.Ox devices was >0.99 in each trial. CONCLUSION: The wireless NIRS flap monitor is capable of detecting StO2 changes resultant from arterial vascular occlusive events. In this porcine flap model, the functionality of this novel sensor closely mirrored that of the T.Ox wired platform. This device is waterproof, highly adhesive, skin conforming, and has sufficient battery life to function for 5 days. Clinical testing is necessary to determine if this wireless functionality translates into fewer false-positive alarms and a better user experience.

5.
Nat Commun ; 12(1): 5008, 2021 08 24.
Artigo em Inglês | MEDLINE | ID: mdl-34429436

RESUMO

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.


Assuntos
Técnicas Biossensoriais/métodos , Fontes de Energia Elétrica , Pressão , Temperatura , Tecnologia sem Fio , Adulto , Idoso , Idoso de 80 Anos ou mais , Técnicas Biossensoriais/instrumentação , Desenho de Equipamento , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Monitorização Fisiológica , Pele , Termografia/instrumentação , Termografia/métodos
6.
Nat Commun ; 12(1): 4374, 2021 07 16.
Artigo em Inglês | MEDLINE | ID: mdl-34272375

RESUMO

Self-powered implantable devices have the potential to extend device operation time inside the body and reduce the necessity for high-risk repeated surgery. Without the technological innovation of in vivo energy harvesters driven by biomechanical energy, energy harvesters are insufficient and inconvenient to power titanium-packaged implantable medical devices. Here, we report on a commercial coin battery-sized high-performance inertia-driven triboelectric nanogenerator (I-TENG) based on body motion and gravity. We demonstrate that the enclosed five-stacked I-TENG converts mechanical energy into electricity at 4.9 µW/cm3 (root-mean-square output). In a preclinical test, we show that the device successfully harvests energy using real-time output voltage data monitored via Bluetooth and demonstrate the ability to charge a lithium-ion battery. Furthermore, we successfully integrate a cardiac pacemaker with the I-TENG, and confirm the ventricle pacing and sensing operation mode of the self-rechargeable cardiac pacemaker system. This proof-of-concept device may lead to the development of new self-rechargeable implantable medical devices.


Assuntos
Fontes de Energia Elétrica , Monitorização Fisiológica/instrumentação , Nanotecnologia/instrumentação , Marca-Passo Artificial , Animais , Fenômenos Biomecânicos , Cães , Eletricidade , Gravitação , Movimento (Física) , Próteses e Implantes , Dispositivos Eletrônicos Vestíveis
7.
Sci Adv ; 7(20)2021 05.
Artigo em Inglês | MEDLINE | ID: mdl-33980495

RESUMO

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.


Assuntos
Acelerometria/instrumentação , Acelerometria/métodos , Eletrocardiografia Ambulatorial/instrumentação , Eletrocardiografia Ambulatorial/métodos , Dispositivos Eletrônicos Vestíveis , Temperatura Corporal , COVID-19 , Exercício Físico/fisiologia , Frequência Cardíaca , Humanos , Monitorização Fisiológica/instrumentação , Monitorização Fisiológica/métodos , SARS-CoV-2
8.
Adv Mater ; 33(25): e2100026, 2021 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-33984170

RESUMO

Recently developed methods for transforming 2D patterns of thin-film materials into 3D mesostructures create many interesting opportunities in microsystems design. A growing area of interest is in multifunctional thermal, electrical, chemical, and optical interfaces to biological tissues, particularly 3D multicellular, millimeter-scale constructs, such as spheroids, assembloids, and organoids. Herein, examples of 3D mechanical interfaces are presented, in which thin ribbons of parylene-C form the basis of transparent, highly compliant frameworks that can be reversibly opened and closed to capture, envelop, and mechanically restrain fragile 3D tissues in a gentle, nondestructive manner, for precise measurements of viscoelastic properties using techniques in nanoindentation. Finite element analysis serves as a design tool to guide selection of geometries and material parameters for shape-matching 3D architectures tailored to organoids of interest. These computational approaches also quantitate all aspects of deformations during the processes of opening and closing the structures and of forces imparted by them onto the surfaces of enclosed soft tissues. Studies of cerebral organoids by nanoindentation show effective Young's moduli in the range from 1.5 to 2.5 kPa depending on the age of the organoid. This collection of results suggests broad utility of compliant 3D mesostructures in noninvasive mechanical measurements of millimeter-scale, soft biological tissues.

9.
Adv Healthc Mater ; 10(17): e2100383, 2021 09.
Artigo em Inglês | MEDLINE | ID: mdl-33938638

RESUMO

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.


Assuntos
Cuidados Críticos , Sinais Vitais , Pressão Sanguínea , Criança , Humanos , Recém-Nascido , Monitorização Fisiológica , Pele
10.
Sci Adv ; 7(12)2021 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-33731359

RESUMO

Three-dimensional (3D), submillimeter-scale constructs of neural cells, known as cortical spheroids, are of rapidly growing importance in biological research because these systems reproduce complex features of the brain in vitro. Despite their great potential for studies of neurodevelopment and neurological disease modeling, 3D living objects cannot be studied easily using conventional approaches to neuromodulation, sensing, and manipulation. Here, we introduce classes of microfabricated 3D frameworks as compliant, multifunctional neural interfaces to spheroids and to assembloids. Electrical, optical, chemical, and thermal interfaces to cortical spheroids demonstrate some of the capabilities. Complex architectures and high-resolution features highlight the design versatility. Detailed studies of the spreading of coordinated bursting events across the surface of an isolated cortical spheroid and of the cascade of processes associated with formation and regrowth of bridging tissues across a pair of such spheroids represent two of the many opportunities in basic neuroscience research enabled by these platforms.

11.
Dev Psychobiol ; 63(5): 1521-1533, 2021 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-33521969

RESUMO

Robust literature supports the positive effects of kangaroo mother care (KMC) on infant physiologic stability and parent-infant bonding in the Neonatal Intensive Care Unit (NICU). Comparatively little is known about kangaroo father care (KFC) in the NICU, and KFC implementation has been limited. Our pilot feasibility study objective was to examine KFC effects on premature infants and fathers as compared to KMC. Parents of preterm NICU infants independently completed a 90-min Kangaroo Care (KC) session on consecutive days. Infant heart rate variability (HRV) and apnea/periodicity measures were compared (pre-KC to KC; KFC to KMC). Additionally, we assessed the feasibility of administering three psychosocial questionnaires to fathers and mothers in the NICU and after discharge. Ten preterm infants completed 20 KC sessions (334/7 -374/7  weeks post-menstrual age). Results demonstrated similar infant physiologic responses between KMC and KFC, including significant differences in measures of HRV (p < .05) between KC and non-KC periods. Eighty-eight percentage of questionnaires administered were completed, supporting the utilization of these instruments in future research of this population. If confirmed, these preliminary results identify an opportunity to objectively assess KFC effects, supporting the development of empirically based KFC programs benefitting NICU families.

12.
Proc Natl Acad Sci U S A ; 117(50): 31674-31684, 2020 12 15.
Artigo em Inglês | MEDLINE | ID: mdl-33257558

RESUMO

The standard of clinical care in many pediatric and neonatal neurocritical care units involves continuous monitoring of cerebral hemodynamics using hard-wired devices that physically adhere to the skin and connect to base stations that commonly mount on an adjacent wall or stand. Risks of iatrogenic skin injuries associated with adhesives that bond such systems to the skin and entanglements of the patients and/or the healthcare professionals with the wires can impede clinical procedures and natural movements that are critical to the care, development, and recovery of pediatric patients. This paper presents a wireless, miniaturized, and mechanically soft, flexible device that supports measurements quantitatively comparable to existing clinical standards. The system features a multiphotodiode array and pair of light-emitting diodes for simultaneous monitoring of systemic and cerebral hemodynamics, with ability to measure cerebral oxygenation, heart rate, peripheral oxygenation, and potentially cerebral pulse pressure and vascular tone, through the utilization of multiwavelength reflectance-mode photoplethysmography and functional near-infrared spectroscopy. Monte Carlo optical simulations define the tissue-probing depths for source-detector distances and operating wavelengths of these systems using magnetic resonance images of the head of a representative pediatric patient to define the relevant geometries. Clinical studies on pediatric subjects with and without congenital central hypoventilation syndrome validate the feasibility for using this system in operating hospitals and define its advantages relative to established technologies. This platform has the potential to substantially enhance the quality of pediatric care across a wide range of conditions and use scenarios, not only in advanced hospital settings but also in clinics of lower- and middle-income countries.


Assuntos
Técnicas Biossensoriais , Circulação Cerebrovascular/fisiologia , Monitorização Hemodinâmica/instrumentação , Transtornos do Neurodesenvolvimento/diagnóstico , Monitorização Neurofisiológica/instrumentação , Adolescente , Criança , Desenvolvimento Infantil/fisiologia , Pré-Escolar , Feminino , Monitorização Hemodinâmica/métodos , Humanos , Lactente , Masculino , Transtornos do Neurodesenvolvimento/fisiopatologia , Monitorização Neurofisiológica/métodos , Espectroscopia de Luz Próxima ao Infravermelho/instrumentação , Dispositivos Eletrônicos Vestíveis , Tecnologia sem Fio/instrumentação
13.
Sci Adv ; 6(49)2020 12.
Artigo em Inglês | MEDLINE | ID: mdl-33277263

RESUMO

Therapeutic compression garments (TCGs) are key tools for the management of a wide range of vascular lower extremity conditions. Proper use of TCGs involves application of a minimum and consistent pressure across the lower extremities for extended periods of time. Slight changes in the characteristics of the fabric and the mechanical properties of the tissues lead to requirements for frequent measurements and corresponding adjustments of the applied pressure. Existing sensors are not sufficiently small, thin, or flexible for practical use in this context, and they also demand cumbersome, hard-wired interfaces for data acquisition. Here, we introduce a flexible, wireless monitoring system for tracking both temperature and pressure at the interface between the skin and the TCGs. Detailed studies of the materials and engineering aspects of these devices, together with clinical pilot trials on a range of patients with different pathologies, establish the technical foundations and measurement capabilities.

14.
Proc Natl Acad Sci U S A ; 117(45): 27906-27915, 2020 11 10.
Artigo em Inglês | MEDLINE | ID: mdl-33106394

RESUMO

Soft microfluidic systems that capture, store, and perform biomarker analysis of microliter volumes of sweat, in situ, as it emerges from the surface of the skin, represent an emerging class of wearable technology with powerful capabilities that complement those of traditional biophysical sensing devices. Recent work establishes applications in the real-time characterization of sweat dynamics and sweat chemistry in the context of sports performance and healthcare diagnostics. This paper presents a collection of advances in biochemical sensors and microfluidic designs that support multimodal operation in the monitoring of physiological signatures directly correlated to physical and mental stresses. These wireless, battery-free, skin-interfaced devices combine lateral flow immunoassays for cortisol, fluorometric assays for glucose and ascorbic acid (vitamin C), and digital tracking of skin galvanic responses. Systematic benchtop evaluations and field studies on human subjects highlight the key features of this platform for the continuous, noninvasive monitoring of biochemical and biophysical correlates of the stress state.


Assuntos
Técnicas Biossensoriais/instrumentação , Microfluídica/métodos , Suor/química , Espectroscopia Dielétrica/instrumentação , Espectroscopia Dielétrica/métodos , Impedância Elétrica , Desenho de Equipamento/instrumentação , Desenho de Equipamento/métodos , Fluorometria , Humanos , Imunoensaio , Dispositivos Lab-On-A-Chip , Pele/química , Dispositivos Eletrônicos Vestíveis
15.
Sci Technol Adv Mater ; 21(1): 683-688, 2020 Sep 28.
Artigo em Inglês | MEDLINE | ID: mdl-33061840

RESUMO

Triboelectric nanogenerators (TENGs) that enable the conversion of a given mechanical energy into electrical energy at high efficiency have been very important in practice. Since the given mechanical energy is involuntarily converted to secondary energy sources (light, heat, and sound during triboelectrification), the significant amount of energy being converted is lost. Various studies have thus been continuously carried out to overcome this issue. Since the first TENGs found in 2012, various developments in TENGs have been made: (1) the mechanical-electrical energy conversion characteristics of potential organic/inorganic material groups have been introduced, (2) the integration into the device structure considering the diversity of mechanical energy, and (3) user friendly and industrial application platforms have been aggressively studied. Despite the remarkable progress and improvement of TENGs, their mechanical-electrical conversion efficiency is still quite low. We therefore need to discover and develop materials that can be converted to improve efficiency. Here, we outline the recent progress made in a group of high polarity triboelectric materials that exploit surface charge density and charge transfer properties. We also review the recent boosting powering TENGs. The aim of this work is to provide insight into the future direction and strategies for highly enhanced powering TENGs through material research.

16.
Sci Adv ; 6(35): eabb1093, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32923633

RESUMO

Implantable drug release platforms that offer wirelessly programmable control over pharmacokinetics have potential in advanced treatment protocols for hormone imbalances, malignant cancers, diabetic conditions, and others. We present a system with this type of functionality in which the constituent materials undergo complete bioresorption to eliminate device load from the patient after completing the final stage of the release process. Here, bioresorbable polyanhydride reservoirs store drugs in defined reservoirs without leakage until wirelessly triggered valve structures open to allow release. These valves operate through an electrochemical mechanism of geometrically accelerated corrosion induced by passage of electrical current from a wireless, bioresorbable power-harvesting unit. Evaluations in cell cultures demonstrate the efficacy of this technology for the treatment of cancerous tissues by release of the drug doxorubicin. Complete in vivo studies of platforms with multiple, independently controlled release events in live-animal models illustrate capabilities for control of blood glucose levels by timed delivery of insulin.

17.
ACS Nano ; 11(11): 10733-10741, 2017 11 28.
Artigo em Inglês | MEDLINE | ID: mdl-28968064

RESUMO

Harvesting human-motion energy for power-integrated wearable electronics could be a promising way to extend the battery-operation time of small low-power-consumption electronics such as various sensors. For this purpose, a fully stretchable triboelectric nanogenerator (S-TENG) that has been fabricated with knitted fabrics and has been integrated with the directly available materials and techniques of the textile industry is introduced. This device has been adapted to cloth movement and can generate electricity under compression and stretching. We investigated plain-, double-, and rib-fabric structures and analyzed their potentials for textile-based energy harvesting. The superior stretchable property of the rib-knitted fabric contributed to a dramatic enhancement of the triboelectric power-generation performance owing to the increased contact surface. The present study shows that, under stretching motions of up to 30%, the S-TENG generates a maximum voltage and a current of 23.50 V and 1.05 µA, respectively, depending on the fabric structures. Under compressions at 3.3 Hz, the S-TENG generated a constant average root-mean square power of up to 60 µW. The results of this work show the feasibility of a cloth-integrated and industrial-ready TENG for the harvesting of energy from human biomechanical movements in cloth and garments.

18.
ACS Appl Mater Interfaces ; 8(34): 22135-41, 2016 Aug 31.
Artigo em Inglês | MEDLINE | ID: mdl-27547841

RESUMO

The high performance of ZnO-based piezoelectric nanogenerators (NGs) has been limited due to the potential screening from intrinsic electron carriers in ZnO. We have demonstrated a novel approach to greatly improve piezoelectric power generation by electrodepositing a high-quality p-type Cu2O layer between the piezoelectric semiconducting film and the metal electrode. The p-n heterojunction using only oxides suppresses the screening effect by forming an intrinsic depletion region, and thus sufficiently enhances the piezoelectric potential, compared to the pristine ZnO piezoelectric NG. Interestingly, a Sb-doped Cu2O layer has high mobility and low surface trap states. Thus, this doped layer is an attractive p-type material to significantly improve piezoelectric performance. Our results revealed that p-n junction NGs consisting of Au/ZnO/Cu2O/indium tin oxide with a Cu2O:Sb (cuprous oxide with a small amount of antimony) layer of sufficient thickness (3 µm) exhibit an extraordinarily high piezoelectric potential of 0.9 V and a maximum output current density of 3.1 µA/cm(2).

19.
ACS Nano ; 10(8): 7297-302, 2016 08 23.
Artigo em Inglês | MEDLINE | ID: mdl-27415838

RESUMO

Recently, several reports have demonstrated that a moving droplet of seawater or ionic solution over monolayer graphene produces an electric power of about 19 nW, and this has been suggested to be a result of the pseudocapacitive effect between graphene and the liquid droplet. Here, we show that the change in the triboelectrification-induced pseudocapacitance between the water droplet and monolayer graphene on polytetrafluoroethylene (PTFE) results in a large power output of about 1.9 µW, which is about 100 times larger than that presented in previous research. During the graphene transfer process, a very strong negative triboelectric potential is generated on the surface of the PTFE. Positive and negative charge accumulation, respectively, occurs on the bottom and the top surfaces of graphene due to the triboelectric potential, and the negative charges that accumulate on the top surface of graphene are driven forward by the moving droplet, charging and discharging at the front and rear of the droplet.

20.
Opt Express ; 23(15): 18864-71, 2015 Jul 27.
Artigo em Inglês | MEDLINE | ID: mdl-26367550

RESUMO

We report a novel ultraviolet photodetector based on graphene/h-BN/ZnO van der Waals heterostructure. Graphene/ZnO heterostructure shows poor rectification behavior and almost no photoresponse. In comparison, graphene/h-BN/ZnO structure shows improved electrical rectified behavior and surprising high UV photoresponse (1350AW(-1)), which is two or three orders magnitude larger than reported GaN UV photodetector (0.2~20AW(-1)). Such high photoresponse mainly originates from the introduction of ultrathin two-dimensional (2D) insulating h-BN layer, which behaves as the tunneling layer for holes produced in ZnO and the blocking layer for holes in graphene. The graphene/h-BN/ZnO heterostructure should be a novel and representative 2D heterostructure for improving the performance of 2D materials/Semiconductor heterostructure based optoelectronic devices.

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