2,710 research outputs found

    Curvy surface conformal ultra-thin transfer printed Si optoelectronic penetrating microprobe arrays

    Get PDF
    Penetrating neural probe arrays are powerful bio-integrated devices for studying basic neuroscience and applied neurophysiology, underlying neurological disorders, and understanding and regulating animal and human behavior. This paper presents a penetrating microprobe array constructed in thin and flexible fashion, which can be seamlessly integrated with the soft curvy substances. The function of the microprobes is enabled by transfer printed ultra-thin Si optoelectronics. As a proof-of-concept device, microprobe array with Si photodetector arrays are demonstrated and their capability of mapping the photo intensity in space are illustrated. The design strategies of utilizing thin polyimide based microprobes and supporting substrate, and employing the heterogeneously integrated thin optoelectronics are keys to accomplish such a device. The experimental and theoretical investigations illustrate the materials, manufacturing, mechanical and optoelectronic aspects of the device. While this paper primarily focuses on the device platform development, the associated materials, manufacturing technologies, and device design strategy are applicable to more complex and multi-functionalities in penetrating probe array-based neural interfaces and can also find potential utilities in a wide range of bio-integrated systems

    Using ultra-thin parylene films as an organic gate insulator in nanowire field-effect transistors

    Full text link
    We report the development of nanowire field-effect transistors featuring an ultra-thin parylene film as a polymer gate insulator. The room temperature, gas-phase deposition of parylene is an attractive alternative to oxide insulators prepared at high temperatures using atomic layer deposition. We discuss our custom-built parylene deposition system, which is designed for reliable and controlled deposition of <100 nm thick parylene films on III-V nanowires standing vertically on a growth substrate or horizontally on a device substrate. The former case gives conformally-coated nanowires, which we used to produce functional Ω\Omega-gate and gate-all-around structures. These give sub-threshold swings as low as 140 mV/dec and on/off ratios exceeding 10310^3 at room temperature. For the gate-all-around structure, we developed a novel fabrication strategy that overcomes some of the limitations with previous lateral wrap-gate nanowire transistors. Finally, we show that parylene can be deposited over chemically-treated nanowire surfaces; a feature generally not possible with oxides produced by atomic layer deposition due to the surface `self-cleaning' effect. Our results highlight the potential for parylene as an alternative ultra-thin insulator in nanoscale electronic devices more broadly, with potential applications extending into nanobioelectronics due to parylene's well-established biocompatible properties

    Breaking the challenge of signal integrity using time-domain spoof surface plasmon polaritons

    Full text link
    In modern integrated circuits and wireless communication systems/devices, three key features need to be solved simultaneously to reach higher performance and more compact size: signal integrity, interference suppression, and miniaturization. However, the above-mentioned requests are almost contradictory using the traditional techniques. To overcome this challenge, here we propose time-domain spoof surface plasmon polaritons (SPPs) as the carrier of signals. By designing a special plasmonic waveguide constructed by printing two narrow corrugated metallic strips on the top and bottom surfaces of a dielectric substrate with mirror symmetry, we show that spoof SPPs are supported from very low frequency to the cutoff frequency with strong subwavelength effects, which can be converted to the time-domain SPPs. When two such plasmonic waveguides are tightly packed with deep-subwavelength separation, which commonly happens in the integrated circuits and wireless communications due to limited space, we demonstrate theoretically and experimentally that SPP signals on such two plasmonic waveguides have better propagation performance and much less mutual coupling than the conventional signals on two traditional microstrip lines with the same size and separation. Hence the proposed method can achieve significant interference suppression in very compact space, providing a potential solution to break the challenge of signal integrity

    High-order localized spoof surface plasmon resonances and experimental verifications

    Full text link
    We theoretically demonstrated and experimentally verified high-order radial spoof localized surface plasmon resonances supported by textured metal particles. Through an effective medium theory and exact numerical simulations, we show the emergence of these geometrically-originated electromagnetic modes at microwave frequencies. The occurrence of high-order radial spoof plasmon resonances is experimentally verified in ultrathin disks. Their spectral and near-field properties are characterized experimentally, showing an excellent agreement with theoretical predictions. Our findings shed light into the nature of spoof localized surface plasmons, and open the way to the design of broadband plasmonic devices able to operate at very different frequency regimes.Comment: 29 pages, 10 figure

    Modeling Light Trapping in Nanostructured Solar Cells

    Get PDF
    The integration of nanophotonic and plasmonic structures with solar cells offers the ability to control and confine light in nanoscale dimensions. These nanostructures can be used to couple incident sunlight into both localized and guided modes, enhancing absorption while reducing the quantity of material. Here we use electromagnetic modeling to study the resonances in a solar cell containing both plasmonic metal back contacts and nanostructured semiconductor top contacts, identify the local and guided modes contributing to enhanced absorption, and optimize the design. We then study the role of the different interfaces and show that Al is a viable plasmonic back contact material

    Transparent and conductive nanomembranes with orthogonal silver nanowire arrays for skin-attachable loudspeakers and microphones

    Get PDF
    We demonstrate ultrathin, transparent, and conductive hybrid nanomembranes (NMs) with nanoscale thickness, consisting of an orthogonal silver nanowire array embedded in a polymer matrix. Hybrid NMs significantly enhance the electrical and mechanical properties of ultrathin polymer NMs, which can be intimately attached to human skin. As a proof of concept, we present a skin-attachable NM loudspeaker, which exhibits a significant enhancement in thermoacoustic capabilities without any significant heat loss from the substrate. We also present a wearable transparent NM microphone combined with a micropyramid-patterned polydimethylsiloxane film, which provides excellent acoustic sensing capabilities based on a triboelectric voltage signal. Furthermore, the NM microphone can be used to provide a user interface for a personal voice-based security system in that it can accurately recognize a user???s voice. This study addressed the NM-based conformal electronics required for acoustic device platforms, which could be further expanded for application to conformal wearable sensors and health care devices

    Experimental observation of superscattering

    Get PDF
    Superscattering, induced by degenerate resonances, breaks the fundamental single-channel limit of scattering cross section of subwavelength structures; in principle, an arbitrarily large total cross section can be achieved via superscattering. It thus provides a unique way to strengthen the light-matter interaction at the subwavelength scale, and has many potential applications in sensing, energy harvesting, bio-imaging (such as magnetic resonance imaging), communication and optoelectronics. However, the experimental demonstration of superscattering remains an open challenge due to its vulnerability to structural imperfections and intrinsic material losses. Here we report the first experimental evidence for superscattering, by demonstrating the superscattering simultaneously in two different frequency regimes through both the far-field and near-field measurements. The underlying mechanism for the observed superscattering is the degenerate resonances of confined surface waves, by utilizing a subwavelength metasurface-based multilayer structure. Our work paves the way towards practical applications based on superscattering

    Bending light to our will

    Get PDF
    This article is based on the Fred Kavli Distinguished Lectureship in Nanoscience presentation given by Harry Atwater (California Institute of Technology) on April 5, 2010 at the Materials Research Society Spring Meeting in San Francisco, CA. The Kavli Foundation supports scientific research, honors scientific achievement, and promotes public understanding of scientists and their work. Its particular focuses are astrophysics, nanoscience, and neuroscience. Solar energy is currently enjoying substantial growth and investment, owing to worldwide sensitivity to energy security and climate change. Solar energy is an inexhaustible resource and is in abundant supply on all continents of the world. The power density of sunlight (~1000 W/m 2 ) and the effi ciency of photovoltaic devices (~10–25%) are high enough so that land use does not limit photovoltaic deployment at the terawatt scale. However solar photovoltaics are currently too expensive to achieve parity with other forms of electricity generation based on fossil fuels. This is largely due to the cost (and for some cases, the abundance) of materials used in photovoltaic modules and systems, and the cost of deploying in current form. This economic and social context has created the present situation where there is widespread interest in photovoltaic technology for power generation, but the cumulative installed world capacity for photovoltaics is <50 GW, and it appears to be very challenging for photovoltaics to play a very substantial role in large-scale (terawatt) electricity generation in the short term

    Aligned Silver Nanowire Networks as Transparent Electrodes for High-Performance Optoelectronics and Electronic Devices

    Get PDF
    Department of Energy EngineeringFlexible transparent electrode is an essential component for several kinds of electronic and optoelectronic applications, such as organic solar cells (OSCs), perovskite solar cells (PSCs), organic light-emitting diodes (OLEDs), touch sensors, and electronic skins (E-skins). Although conventional indium tin oxide (ITO) has been widely used in commercial transparent electrodes, it still shows a limitation in the fabrication of flexible transparent electrodes for applications in flexible/wearable electronic devices because of their inherent brittleness. Among various alternatives of ITO, silver nanowire (AgNW) network has been considered as promising conductive nano-material due to their high electrical conductivity, excellent transmittance, and mechanical flexibility that can be readily deposited by cost-effective and large-scale solution process. However, random AgNW networks prepared by solution processing have several drawbacks, such as high junction resistance between nanowires (NWs), low transmittance, haze issues, and rough surface morphologies, resulting in a degradation of the device performance. Electrical and optical properties of random AgNW networks can be strongly affected by controlling NW density, electrical current path, and junction resistance related to conductive percolated networks. Therefore, manipulating the assembled structure of AgNW network can provide powerful platforms to realize ideal flexible transparent electrodes with high electrical conductivity, superior transmittance, and smooth surface morphologies for achieving high-performance electronic and optoelectronic device. In this thesis, we introduce aligned AgNW transparent electrodes and their applications in flexible optoelectronic and functional electronic devices. Firstly, Chapter 1 introduces the research tends in transparent electrodes and several issues of AgNW networks that should be carefully considered in the fabrication for their potential device applications. In chapter 2, we demonstrate the capillary printing technique to make highly aligned AgNW network to fabricate high-performance transparent electrodes for improving device efficiency of optoelectronic devices including OSCs and OLEDs. In Chapter 3, we demonstrate the fabrication of nanoparticle (NP)-enhanced plasmonic AgNW electrode for high-performance optoelectronic devices in which the NP-NW hybrid plasmonic system generates gap plasmonic coupling which induces a large electric field enhancement, resulting in an improvement of the device efficiency in both OSC and OLED devices. In Chapter 4, we demonstrate the fabrication of ultrathin and flexible perovskite solar cell foils with orthogonal AgNW electrodes, which exhibits high power-per-weight performance as well as a conformal contact capability to curvilinear surface. In Chapter 5, we introduce a large-scale assembly technique to uniformly align AgNW arrays for the fabrication of large area transparent electrodes, where cross-aligned AgNW network shows better electrical and optical properties as well as large-scale uniformity than random AgNW network. For the proof of the concept demonstration, we fabricated a flexible force-sensitive touch screen panel integrated with a mechanochromic polymer film. Finally, we introduce a transparent and conductive nano-membrane (NM) incorporated with orthogonal AgNW arrays in Chapter 6, which exhibits enhanced electrical and mechanical properties than pure polymeric NMs. To show the unique properties of these hybrid NMs for potential device applications, we demonstrate skin-attachable thermoacoustic-based NM loudspeaker and wearable NM microphone, both of which show much improved device performances compared to conventional thin film-based devices. In this thesis, studies on aligned AgNW transparent electrodes and their device applications could be further expanded for diverse flexible and wearable optoelectronic and electronic applications, such as conformal wearable sensors, healthcare monitoring devices, and wearable plasmonic devices.clos
    corecore