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1.
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.

2.
Sci Transl Med ; 12(574)2020 12 16.
Artigo em Inglês | MEDLINE | ID: mdl-33328330

RESUMO

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.


Assuntos
Membros Artificiais , Fontes de Energia Elétrica , Desenho de Prótese , Pele , Temperatura
3.
Nat Med ; 26(3): 418-429, 2020 03.
Artigo em Inglês | MEDLINE | ID: mdl-32161411

RESUMO

Standard clinical care in neonatal and pediatric intensive-care units (NICUs and PICUs, respectively) involves continuous monitoring of vital signs with hard-wired devices that adhere to the skin and, in certain instances, can involve catheter-based pressure sensors inserted into the arteries. These systems entail risks of causing iatrogenic skin injuries, complicating clinical care and impeding skin-to-skin contact between parent and child. Here we present a wireless, non-invasive technology that not only offers measurement equivalency to existing clinical standards for heart rate, respiration rate, temperature and blood oxygenation, but also provides a range of important additional features, as supported by data from pilot clinical studies in both the NICU and PICU. These new modalities include tracking movements and body orientation, quantifying the physiological benefits of skin-to-skin care, capturing acoustic signatures of cardiac activity, recording vocal biomarkers associated with tonality and temporal characteristics of crying and monitoring a reliable surrogate for systolic blood pressure. These platforms have the potential to substantially enhance the quality of neonatal and pediatric critical care.


Assuntos
Técnicas Biossensoriais , Unidades de Terapia Intensiva Neonatal , Unidades de Terapia Intensiva Pediátrica , Monitorização Fisiológica , Pele/anatomia & histologia , Tecnologia sem Fio , Monitorização Ambulatorial da Pressão Arterial , Criança , Pré-Escolar , Eletrocardiografia , Desenho de Equipamento , Humanos , Recém-Nascido , Fotopletismografia , Fatores de Tempo
4.
Nanotechnology ; 29(32): 325502, 2018 Aug 10.
Artigo em Inglês | MEDLINE | ID: mdl-29786618

RESUMO

We investigated the acoustic performance of electrostatic sound-generating devices consisting of bi-layer graphene on polyimide film. The total sound pressure level (SPL) of the sound generated from the devices was measured as a function of source frequency by sweeping, and frequency spectra were measured at 1/3 octave band frequencies. The relationship between various operation conditions and total SPL was determined. In addition, the effects of changing voltage level, adding a DC offset, and using two pairs of electrodes were evaluated. It should be noted that two pairs of electrode operations improved sound generation by about 10 dB over all frequency ranges compared with conventional operation. As for the sound-generating capability, total SPL was 70 dBA at 4 kHz when an AC voltage of 100 Vpp was applied with a DC offset of 100 V. Acoustic characteristics differed from other types of graphene-based sound generators, such as graphene thermoacoustic devices and graphene polyvinylidene fluoride devices. The effects of diameter and distance between electrodes were also studied, and we found that diameter greatly influenced the frequency response. We anticipate that the design information provided in this paper, in addition to describing key parameters of electrostatic sound-generating devices, will facilitate the commercial development of electrostatic sound-generating systems.

5.
J Opt Soc Am A Opt Image Sci Vis ; 33(10): 2099-2107, 2016 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-27828119

RESUMO

In this study, a method of evaluating and enhancing the visibility of graphene oxide on dielectric films was investigated. To evaluate the visibility in a multiwavelength range, we have suggested two parameters, the red, green, and blue (RGB) contrast and the RGB difference. By using these two parameters, researchers can easily determine whether the visibility comes from the color difference or from the intensity difference between the material and substrate. A high contrast image can be acquired by filtering the light source with color filters. It is predicted that the visibility of the graphene oxide monolayer may be three times as high under normal halogen light. By measurement, the visibility of graphene oxide on 70 nm Si3N4/Si increased 2.67±0.13 times under a green-filtered light. The calculated colors of graphene oxide from the RGB parameter can be effectively used to estimate the graphene oxide layer thickness and effective dielectric film thickness for high visibility graphene oxide.

6.
Appl Opt ; 54(28): 8265-70, 2015 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-26479594

RESUMO

In this paper, flexible hemispherical lens arrays based on soft elastomers were fabricated. Then, the effects of various geometric parameters on the deformation (i.e., hemispherical deformation and radial extension) of these lens arrays were investigated experimentally and were verified by finite element analysis. We focused on determining the relationship between the geometric parameters and the radius of curvature of the lens. We found that the height of the lens support post plays an important role in minimizing changes in the radius of curvature of the lens. The results of this research offer valuable design principles for flexible lens arrays, which can be used as an optical component of various flexible optoelectronic devices.

7.
Nature ; 497(7447): 95-9, 2013 May 02.
Artigo em Inglês | MEDLINE | ID: mdl-23636401

RESUMO

In arthropods, evolution has created a remarkably sophisticated class of imaging systems, with a wide-angle field of view, low aberrations, high acuity to motion and an infinite depth of field. A challenge in building digital cameras with the hemispherical, compound apposition layouts of arthropod eyes is that essential design requirements cannot be met with existing planar sensor technologies or conventional optics. Here we present materials, mechanics and integration schemes that afford scalable pathways to working, arthropod-inspired cameras with nearly full hemispherical shapes (about 160 degrees). Their surfaces are densely populated by imaging elements (artificial ommatidia), which are comparable in number (180) to those of the eyes of fire ants (Solenopsis fugax) and bark beetles (Hylastes nigrinus). The devices combine elastomeric compound optical elements with deformable arrays of thin silicon photodetectors into integrated sheets that can be elastically transformed from the planar geometries in which they are fabricated to hemispherical shapes for integration into apposition cameras. Our imaging results and quantitative ray-tracing-based simulations illustrate key features of operation. These general strategies seem to be applicable to other compound eye devices, such as those inspired by moths and lacewings (refracting superposition eyes), lobster and shrimp (reflecting superposition eyes), and houseflies (neural superposition eyes).


Assuntos
Artrópodes/anatomia & histologia , Biomimética , Olho Composto de Artrópodes/anatomia & histologia , Óptica e Fotônica/instrumentação , Fotografação/instrumentação , Animais , Formigas/anatomia & histologia , Materiais Biomiméticos/química , Besouros/anatomia & histologia , Endoscópios , Silício
8.
Nanotechnology ; 23(2): 025708, 2012 Jan 20.
Artigo em Inglês | MEDLINE | ID: mdl-22166791

RESUMO

We investigated the colors of graphene and graphene-oxide multilayers that were deposited on various dielectric layers. In particular, the effects of the material thickness, the types of dielectric layers, and the existence of a back silicon substrate were analyzed. The colors of graphene-oxide layers on a SiO2/Si substrate were found to periodically change as the material thickness increased. However, the colors of graphene layers on the same substrate became saturated without a similar periodic change. The calculated colors corresponding to the material thicknesses were verified by optical microscopy and profilometry. We believe that these results demonstrate the possibility of utilizing color as a simple tool for detecting and estimating the thicknesses of graphene and graphene-oxide multilayers.

9.
Proc Natl Acad Sci U S A ; 108(5): 1788-93, 2011 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-21245356

RESUMO

Imaging systems that exploit arrays of photodetectors in curvilinear layouts are attractive due to their ability to match the strongly nonplanar image surfaces (i.e., Petzval surfaces) that form with simple lenses, thereby creating new design options. Recent work has yielded significant progress in the realization of such "eyeball" cameras, including examples of fully functional silicon devices capable of collecting realistic images. Although these systems provide advantages compared to those with conventional, planar designs, their fixed detector curvature renders them incompatible with changes in the Petzval surface that accompany variable zoom achieved with simple lenses. This paper describes a class of digital imaging device that overcomes this limitation, through the use of photodetector arrays on thin elastomeric membranes, capable of reversible deformation into hemispherical shapes with radii of curvature that can be adjusted dynamically, via hydraulics. Combining this type of detector with a similarly tunable, fluidic plano-convex lens yields a hemispherical camera with variable zoom and excellent imaging characteristics. Systematic experimental and theoretical studies of the mechanics and optics reveal all underlying principles of operation. This type of technology could be useful for night-vision surveillance, endoscopic imaging, and other areas that require compact cameras with simple zoom optics and wide-angle fields of view.

10.
Nature ; 465(7296): 329-33, 2010 May 20.
Artigo em Inglês | MEDLINE | ID: mdl-20485431

RESUMO

Compound semiconductors like gallium arsenide (GaAs) provide advantages over silicon for many applications, owing to their direct bandgaps and high electron mobilities. Examples range from efficient photovoltaic devices to radio-frequency electronics and most forms of optoelectronics. However, growing large, high quality wafers of these materials, and intimately integrating them on silicon or amorphous substrates (such as glass or plastic) is expensive, which restricts their use. Here we describe materials and fabrication concepts that address many of these challenges, through the use of films of GaAs or AlGaAs grown in thick, multilayer epitaxial assemblies, then separated from each other and distributed on foreign substrates by printing. This method yields large quantities of high quality semiconductor material capable of device integration in large area formats, in a manner that also allows the wafer to be reused for additional growths. We demonstrate some capabilities of this approach with three different applications: GaAs-based metal semiconductor field effect transistors and logic gates on plates of glass, near-infrared imaging devices on wafers of silicon, and photovoltaic modules on sheets of plastic. These results illustrate the implementation of compound semiconductors such as GaAs in applications whose cost structures, formats, area coverages or modes of use are incompatible with conventional growth or integration strategies.

11.
Small ; 6(7): 851-6, 2010 Apr 09.
Artigo em Inglês | MEDLINE | ID: mdl-20205199

RESUMO

The fabrication of a hemispherical electronic-eye camera with optimized designs based upon micromechanical analysis is reported. The photodetector arrays combine layouts with multidevice tiles and extended, non-coplanar interconnects to improve the fill factor and deformability, respectively. Quantitative comparison to micromechanics analysis reveals the key features of these designs. Color images collected with working cameras demonstrate the utility of these approaches.


Assuntos
Eletrônica/instrumentação , Fenômenos Mecânicos , Dispositivos Ópticos , Fotografação/instrumentação , Silício/química
12.
Opt Express ; 18(26): 27346-58, 2010 Dec 20.
Artigo em Inglês | MEDLINE | ID: mdl-21197013

RESUMO

Model calculations and the experimental measurements of the imaging properties of planar, hemispherical, and elliptic parabolic electronic eye cameras are compared. Numerical methods for comprehensive full field calculations of image formation are enabled by use computationally efficient modes. Quantitative agreement between these calculations and experimentally measured images of test patterns reveals advantages of curvilinear camera systems, and provides guidelines for future designs.


Assuntos
Materiais Biomiméticos , Aumento da Imagem/instrumentação , Lentes , Fenômenos Fisiológicos Oculares , Fotografação/instrumentação , Animais , Desenho Assistido por Computador , Desenho de Equipamento , Análise de Falha de Equipamento , Humanos
13.
Science ; 324(5932): 1312-4, 2009 Jun 05.
Artigo em Inglês | MEDLINE | ID: mdl-19423775

RESUMO

Graphene has been attracting great interest because of its distinctive band structure and physical properties. Today, graphene is limited to small sizes because it is produced mostly by exfoliating graphite. We grew large-area graphene films of the order of centimeters on copper substrates by chemical vapor deposition using methane. The films are predominantly single-layer graphene, with a small percentage (less than 5%) of the area having few layers, and are continuous across copper surface steps and grain boundaries. The low solubility of carbon in copper appears to help make this growth process self-limiting. We also developed graphene film transfer processes to arbitrary substrates, and dual-gated field-effect transistors fabricated on silicon/silicon dioxide substrates showed electron mobilities as high as 4050 square centimeters per volt per second at room temperature.

14.
Nano Lett ; 9(4): 1593-7, 2009 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-19265429

RESUMO

We report that homogeneous colloidal suspensions of chemically modified graphene sheets were readily produced in a wide variety of organic solvent systems. Two different sets of solubility parameters are used to rationalize when stable colloidal suspensions of graphene oxide sheets and, separately, of reduced graphene oxide sheets in a given solvent type are possible and when they are not. As an example of the utility of such colloidal suspensions, "paperlike" materials generated by very simple filtration of the reduced graphene oxide sheets had electrical conductivity values as high as 16,000 S/m.

15.
Nano Lett ; 8(12): 4283-7, 2008 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-19367929

RESUMO

Step-by-step controllable thermal reduction of individual graphene oxide sheets, incorporated into multiterminal field effect devices, was carried out at low temperatures (125-240 degrees C) with simultaneous electrical measurements. Symmetric hysteresis-free ambipolar (electron- and hole-type) gate dependences were observed as soon as the first measurable resistance was reached. The conductivity of each of the fabricated devices depended on the level of reduction (was increased more than 10(6) times as reduction progressed), strength of the external electrical field, density of the transport current, and temperature.

16.
Nano Lett ; 7(7): 1888-92, 2007 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-17592880

RESUMO

Transparent and electrically conductive composite silica films were fabricated on glass and hydrophilic SiOx/silicon substrates by incorporation of individual graphene oxide sheets into silica sols followed by spin-coating, chemical reduction, and thermal curing. The resulting films were characterized by SEM, AFM, TEM, low-angle X-ray reflectivity, XPS, UV-vis spectroscopy, and electrical conductivity measurements. The electrical conductivity of the films compared favorably to those of composite thin films of carbon nanotubes in silica.


Assuntos
Condutividade Elétrica , Nanotecnologia , Nanotubos de Carbono/química , Dióxido de Silício/química
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