The Experts below are selected from a list of 1248 Experts worldwide ranked by ideXlab platform
George Barbastathis - One of the best experts on this subject based on the ideXlab platform.
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double cone nanostructures for ultimate anti reflectivity of encapsulated silicon solar cells
International Conference on Optical MEMS and Nanophotonics, 2014Co-Authors: Jeonggil Kim, Hyungryul J Choi, Sagrario Dominguez, Ignacio Cornago, George BarbastathisAbstract:Double cone nanostructures are proposed for the ultimate anti-reflectivity of encapsulated silicon solar cells. The proposed design consists of high aspect ratio silicon Nanocones covered by a polymeric layer textured with inverted Nanocone structures. Both Nanocones and inverted Nanocones effectively suppress Fresnel reflection at each interface by means of gradient index effect, while the inverted Nanocones on the top surface provide enhanced mechanical robustness. Also, the proposed design is fabricated using methods compatible with large-scale replication, which have potential to be applied to the energy industry.
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multifunctional inverted Nanocone arrays for non wetting self cleaning transparent surface with high mechanical robustness
Small, 2014Co-Authors: Jeonggil Kim, Hyungryul J Choi, Kyoochul Park, Robert E Cohen, Gareth H Mckinley, George BarbastathisAbstract:A multifunctional surface that enables control of wetting, optical reflectivity and mechanical damage of nanostructured interfaces is presented. Our approach is based on imprinting a periodic array of nanosized cones into a UV-curable polyurethane acrylate (PUA), resulting in a self-reinforcing egg-crate topography evenly distributed over large areas up to several cm(2) in size. The resulting surfaces can be either superhydrophilic or superhydrophobic (through subsequent application of an appropriate chemical coating), they minimize optical reflection losses over a broad range of wavelengths and a wide range of angles of incidence, and they also have enhanced mechanical resilience due to greatly improved redistribution of the normal and shearing mechanical loads. The transmissivity and wetting characteristics of the nanoscale egg-crate structure, as well as its resistance to mechanical deformation are analyzed theoretically. Experiments show that the optical performance together with self-cleaning or anti-fogging behavior of the inverted Nanocone topography is comparable to earlier designs that have used periodic arrays of Nanocones to control reflection and wetting. However the egg-crate structures are far superior in terms of mechanical robustness, and the ability to replicate this topography through several generations is promising for large-scale commercial applications where multifunctionality is important.
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fabrication of ultra high aspect ratio silica Nanocone arrays by multiple shrinking mask etching
International Conference on Optical MEMS and Nanophotonics, 2012Co-Authors: Hyungryul J Choi, Jeonggil Kim, Ignacio Cornago, Tim Savas, George BarbastathisAbstract:We propose and experimentally demonstrate a novel method to fabricate subwavelength silica Nanocone arrays with high aspect ratio (∼7) for multifunctional surfaces having anti-reflective, self-cleaning, and anti-fogging properties.
Eli Vlaisavljevich - One of the best experts on this subject based on the ideXlab platform.
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bubble cloud behavior and ablation capacity for histotripsy generated from intrinsic or artificial cavitation nuclei
Ultrasound in Medicine and Biology, 2020Co-Authors: Connor Edsall, Zerin Mahzabin Khan, Lauren Mancia, Sarah Hall, Waleed Mustafa, Eric Johnsen, Alexander L Klibanov, Yasemin Yuksel Durmaz, Eli VlaisavljevichAbstract:Abstract The study described here examined the effects of cavitation nuclei characteristics on histotripsy. High-speed optical imaging was used to compare bubble cloud behavior and ablation capacity for histotripsy generated from intrinsic and artificial cavitation nuclei (gas-filled microbubbles, fluid-filled Nanocones). Results showed a significant decrease in the cavitation threshold for microbubbles and Nanocones compared with intrinsic-nuclei controls, with predictable and well-defined bubble clouds generated in all cases. Red blood cell experiments showed complete ablations for intrinsic and Nanocone phantoms, but only partial ablation in microbubble phantoms. Results also revealed a lower rate of ablation in artificial-nuclei phantoms because of reduced bubble expansion (and corresponding decreases in stress and strain). Overall, this study demonstrates the potential of using artificial nuclei to reduce the histotripsy cavitation threshold while highlighting differences in the bubble cloud behavior and ablation capacity that need to be considered in the future development of these approaches.
M M Fogler - One of the best experts on this subject based on the ideXlab platform.
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imaging of anomalous internal reflections of hyperbolic phonon polaritons in hexagonal boron nitride
Nano Letters, 2016Co-Authors: Alexander J Giles, Siyuan Dai, O J Glembocki, Andrey V Kretinin, Zhiyuan Sun, Chase T Ellis, J G Tischler, Takashi Taniguchi, Kenji Watanabe, M M FoglerAbstract:We use scanning near-field optical microscopy to study the response of hexagonal boron nitride Nanocones at infrared frequencies, where this material behaves as a hyperbolic medium. The obtained images are dominated by a series of "hot" rings that occur on the sloped sidewalls of the Nanocones. The ring positions depend on the incident laser frequency and the Nanocone shape. Both dependences are consistent with directional propagation of hyperbolic phonon-polariton rays that are launched at the edges and zigzag through the interior of the Nanocones, sustaining multiple internal reflections off the sidewalls. Additionally, we observe a strong overall enhancement of the near-field signal at discrete resonance frequencies. These resonances attest to low dielectric losses that permit coherent standing waves of the subdiffractional polaritons to form. We comment on potential applications of such shape-dependent resonances and the field concentration at the hot rings.
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Imaging of Anomalous Internal Reflections of Hyperbolic Phonon-Polaritons in Hexagonal Boron Nitride
2016Co-Authors: Alexander J Giles, Siyuan Dai, O J Glembocki, Andrey V Kretinin, Zhiyuan Sun, Chase T Ellis, J G Tischler, Takashi Taniguchi, Kenji Watanabe, M M FoglerAbstract:We use scanning near-field optical microscopy to study the response of hexagonal boron nitride Nanocones at infrared frequencies, where this material behaves as a hyperbolic medium. The obtained images are dominated by a series of “hot” rings that occur on the sloped sidewalls of the Nanocones. The ring positions depend on the incident laser frequency and the Nanocone shape. Both dependences are consistent with directional propagation of hyperbolic phonon-polariton rays that are launched at the edges and zigzag through the interior of the Nanocones, sustaining multiple internal reflections off the sidewalls. Additionally, we observe a strong overall enhancement of the near-field signal at discrete resonance frequencies. These resonances attest to low dielectric losses that permit coherent standing waves of the subdiffractional polaritons to form. We comment on potential applications of such shape-dependent resonances and the field concentration at the hot rings
Connor Edsall - One of the best experts on this subject based on the ideXlab platform.
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bubble cloud behavior and ablation capacity for histotripsy generated from intrinsic or artificial cavitation nuclei
Ultrasound in Medicine and Biology, 2020Co-Authors: Connor Edsall, Zerin Mahzabin Khan, Lauren Mancia, Sarah Hall, Waleed Mustafa, Eric Johnsen, Alexander L Klibanov, Yasemin Yuksel Durmaz, Eli VlaisavljevichAbstract:Abstract The study described here examined the effects of cavitation nuclei characteristics on histotripsy. High-speed optical imaging was used to compare bubble cloud behavior and ablation capacity for histotripsy generated from intrinsic and artificial cavitation nuclei (gas-filled microbubbles, fluid-filled Nanocones). Results showed a significant decrease in the cavitation threshold for microbubbles and Nanocones compared with intrinsic-nuclei controls, with predictable and well-defined bubble clouds generated in all cases. Red blood cell experiments showed complete ablations for intrinsic and Nanocone phantoms, but only partial ablation in microbubble phantoms. Results also revealed a lower rate of ablation in artificial-nuclei phantoms because of reduced bubble expansion (and corresponding decreases in stress and strain). Overall, this study demonstrates the potential of using artificial nuclei to reduce the histotripsy cavitation threshold while highlighting differences in the bubble cloud behavior and ablation capacity that need to be considered in the future development of these approaches.
Cosimo Gorini - One of the best experts on this subject based on the ideXlab platform.
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magnetoconductance quantum hall effect and coulomb blockade in topological insulator Nanocones
Physical Review Letters, 2020Co-Authors: Raphael Kozlovsky, Ansgar Graf, Denis Kochan, Klaus Richter, Cosimo GoriniAbstract:Magnetotransport through cylindrical topological insulator (TI) nanowires is governed by the interplay between quantum confinement and geometric (Aharonov-Bohm and Berry) phases. Here, we argue that the much broader class of TI nanowires with varying radius -- for which a homogeneous coaxial magnetic field induces a varying Aharonov-Bohm flux that gives rise to a non-trivial mass-like potential along the wire -- is accessible by studying its simplest member, a TI Nanocone. Such Nanocones allow to observe intriguing mesoscopic transport phenomena: While the conductance in a perpendicular magnetic field is quantized due to higher-order topological hinge states, it shows resonant transmission through Dirac Landau levels in a coaxial magnetic field. Furthermore, it may act as a quantum magnetic bottle, confining surface Dirac electrons and leading to Coulomb blockade. We show numerically that the above-mentioned effects occur for experimentally accessible values of system size and magnetic field, suggesting that TI Nanocone junctions may serve as building blocks for Dirac electron optics setups.
