Science

Sunday, July 1, 2012

Scientific Reports

2,

Article number:

481

doi:10.1038/srep00481

Received

13 April 2012

Accepted

07 June 2012

Published

28 June 2012

If the components of a battery, including electrodes, separator, electrolyte and the current collectors can be designed as paints and applied sequentially to build a complete battery, on any arbitrary surface, it would have significant impact on the design, implementation and integration of energy storage devices. Here, we establish a paradigm change in battery assembly by fabricating rechargeable Li-ion batteries solely by multi-step spray painting of its components on a variety of materials such as metals, glass, glazed ceramics and flexible polymer substrates. We also demonstrate the possibility of interconnected modular spray painted battery units to be coupled to energy conversion devices such as solar cells, with possibilities of building standalone energy capture-storage hybrid devices in different configurations.

Voltage-Gated Ion Transport through Semiconducting Conical Nanopores Formed by Metal Nanoparticle-Assisted Plasma Etching

Teena James†, Yevgeniy V. Kalinin†, Chih-ChiehChan†, Jatinder S. Randhawa†, Mikhail Gaevski§, andDavid H. Gracias*†‡

^†Department of Chemical and Biomolecular Engineering and ^‡Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, United States

^§ Princeton Institute for the Science and Technology of Materials, Princeton University, Princeton, New Jersey 08540, United States

Nano Lett., Article ASAP

DOI: 10.1021/nl300673r

Publication Date (Web): June 22, 2012

Nanopores with conical geometries have been found to rectify ionic current in electrolytes. While nanopores in semiconducting membranes are known to modulate ionic transport through gated modification of pore surface charge, the fabrication of conical nanopores in silicon (Si) has proven challenging. Here, we report the discovery that gold (Au) nanoparticle (NP)-assisted plasma etching results in the formation of conical etch profiles in Si. These conical profiles result due to enhanced Si etch rates in the vicinity of the Au NPs. We show that this process provides a convenient and versatile means to fabricate conical nanopores in Si membranes and crystals with variable pore-diameters and cone-angles. We investigated ionic transport through these pores and observed that rectification ratios could be enhanced by a factor of over 100 by voltage gating alone, and that these pores could function as ionic switches with high on–off ratios of approximately 260. Further, we demonstrate voltage gated control over protein transport, which is of importance in lab-on-a-chip devices and biomolecular separations.

Atomic Force Microscopy with Nanoscale Cantilevers Resolves Different Structural Conformations of the DNA Double Helix

Carl Leung*†, Aizhan Bestembayeva†‡, RichardThorogate†, Jake Stinson†‡, Alice Pyne†§, ChristianMarcovich†

, Jinling Yang

, Ute Drechsler#, MichelDespont#, Tilo Jankowski

, Martin Tschöpe

, andBart W. Hoogenboom*†‡

^† London Centre for Nanotechnology, University College London, 17−19 Gordon Street, London WC1H 0AH, United Kingdom

^‡ Department of Physics and Astronomy,University College London, Gower Street, London WC1E 6BT, United Kingdom

^§ National Physical Laboratory, Hampton Road, Teddington TW11 0LW, United Kingdom

École Polytechnique, 91128 Palaiseau Cedex, France

Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083, P. R. China

^# IBM Research Division, Zurich Research Laboratory, Säumerstrasse 4, 8803 Rüschlikon, Switzerland

JPK Instruments AG, Bouchéstrasse 12, 12435 Berlin, Germany

Nano Lett., Article ASAP

DOI: 10.1021/nl301857p

Publication Date (Web): June 26, 2012

Structural variability and flexibility are crucial factors for biomolecular function. Here we have reduced the invasiness and enhanced the spatial resolution of atomic force microscopy(AFM) to visualize, for the first time, different structural conformations of the two polynucleotide strands in the DNA double helix, for single molecules under near-physiological conditions. This is achieved by identifying and tracking the anomalous resonance behavior of nanoscale AFM cantilevers in the immediate vicinity of the sample.

Adiabatic Nanofocusing on Ultrasmooth Single-Crystalline Gold Tapers Creates a 10-nm-Sized Light Source with Few-Cycle Time Resolution

Slawa Schmidt†, Björn Piglosiewicz†, Diyar Sadiq†,Javid Shirdel†, Jae Sung Lee‡, Parinda Vasa†,Namkyoo Park‡, Dai-Sik Kim§, and Christoph Lienau†*

^† Institut für Physik, Carl von Ossietzky Universität, 26111 Oldenburg, Germany

^‡ Photonic Systems Laboratory, School of EECS, Seoul National University, Seoul 151-744, Korea

^§ Center for Subwavelength Optics and Department of Physics and Astronomy, Seoul National University, Seoul 151-747, Korea

ACS Nano, Article ASAP

DOI: 10.1021/nn301121h

Publication Date (Web): June 8, 2012

We demonstrate adiabatic nanofocusing of few-cycle light pulses using ultrasharp and ultrasmooth single-crystalline gold tapers. We show that the grating-induced launching of spectrally broad-band surface plasmon polariton wavepackets onto the shaft of such a taper generates isolated, point-like light spots with 10 fs duration and 10 nm diameter spatial extent at its very apex. This nanofocusing is so efficient that nanolocalized electric fields inducing strong optical nonlinearities at the tip end are reached with conventional high repetition rate laser oscillators. We use here the resulting second harmonic to fully characterize the time structure of the localized electric field in frequency-resolved interferometric autocorrelation measurements. Our results strongly suggest that these nanometer-sized ultrafast light spots will enable new experiments probing the dynamics of optical excitations of individual metallic, semiconducting, and magnetic nanostructures.

Sunday, May 6, 2012

Shape-Programmed Folding of Stimuli-Responsive Polymer Bilayers

Georgi Stoychev†‡, Svetlana Zakharchenko†‡, Sébastien Turcaud§, John W. C. Dunlop§, and Leonid Ionov†*

^† Leibniz Institute of Polymer Research Dresden, Hohe Straße 6, D-01069 Dresden, Germany and Department of Biomaterials

^‡ Technische Universität Dresden, Physical Chemistry of Polymer Materials, 01062 Dresden, Germany

^§ Max Planck Institute of Colloids and Interfaces

ACS Nano, Article ASAP

DOI: 10.1021/nn300079f

Publication Date (Web): April 24, 2012

We investigated the folding of rectangular stimuli-responsive hydrogel-based polymer bilayers with different aspect ratios and relative thicknesses placed on a substrate. It was found that long-side rolling dominates at high aspect ratios (ratio of length to width) when the width is comparable to the circumference of the formed tubes, which corresponds to a small actuation strain. Rolling from all sides occurs for higher actuation, namely when the width and length considerably exceed the deformed circumference. In the case of moderate actuation, when both the width and length are comparable to the deformed circumference, diagonal rolling is observed. Short-side rolling was observed very rarely and in combination with diagonal rolling. On the basis of experimental observations, finite-element modeling and energetic considerations, we argued that bilayers placed on a substrate start to roll from corners due to quicker diffusion of water. Rolling from the long-side starts later but dominates at high aspect ratios, in agreement with energetic considerations. We have shown experimentally and by modeling that the main reasons causing a variety of rolling scenarios are (i) non-homogenous swelling due to the presence of the substrate and (ii) adhesion of the polymer to the substrate.

Controlling Nanoscale Friction through the Competition between Capillary Adsorption and Thermally Activated Sliding

Christian Greiner†, Jonathan R. Felts‡, Zhenting Dai‡, William P. King‡, and Robert W. Carpick†*

^† Department for Mechanical Engineering and Applied Mechanics, University of Pennsylvania, 112 Towne Building, 220 South 33rd Street, Philadelphia, Pennsylvania 19104, United States,

^‡ Department of Mechanical Science and Engineering,University of Illinois at Urbana—Champaign, 242 Mechanical Engineering Building, 1206 West Green Street, Urbana, Illinois 61801, United States

We demonstrate measurement and control of nanoscale single-asperity friction by using cantilever probes featuring an in situ solid-state heater in contact with silicon oxide substrates. The heater temperature was varied between 25 and 790 °C. By using a low thermal conductivity sample, silicon oxide, we are able to vary tip temperatures over a broad range from 25 ± 2 to 255 ± 25 °C. In ambient atmosphere with

30% relative humidity, the control of friction forces was achieved through the formation of a capillary bridge whose characteristics exhibit a strong dependence on temperature and sliding speed. The capillary condensation is observed to be a thermally activated process, such that heating in ambient air caused friction to increase due to the capillary bridge nucleating and growing. Above tip temperatures of

100 ± 10 °C, friction decreased drastically, which we attribute to controllably evaporating water from the contact at the nanoscale. In contrast, in a dry nitrogen atmosphere, friction was not affected appreciably by temperature changes. In the presence of a capillary, friction decreases at higher sliding speeds due to disruption of the capillary; otherwise, friction increases in accordance with the predictions of a thermally assisted sliding model. In ambient atmospheres, the rate of increase of friction with sliding speed at room temperature is sufficiently strong that the friction force changes from being smaller than the response at 76 ± 8 °C to being larger. Thus, an appropriate change in temperature can cause friction to increase at one sliding speed, while it decreases at another speed.

Angle-Independent Reflectors: Flexible, Angle-Independent, Structural Color Reflectors Inspired by Morpho Butterfly Wings

Kyungjae Chung¹,

Sunkyu Yu²,

Chul-Joon Heo³,

Jae Won Shim³,

Seung-Man Yang³,

Moon Gyu Han⁴,

Hong-Seok Lee⁴,

Yongwan Jin⁴,

Sang Yoon Lee⁴,

Namkyoo Park²,

Jung H. Shin^1,*

Article first published online: 2 MAY 2012

DOI: 10.1002/adma.201290105

The image shows a schematic representation of close-packed multilayer reflecting columns with the same periodicity but with random variations in location, both in horizontal and vertical dimensions, that form the Morpho-mimetic thin-film structural color reflectors described in the manuscript by J. H. Shin and co-workers, on page 2375. Overlaid are photographs of an actual Morpho butterfly, a 6-inch diameter Morpho-mimetic thin film that demonstrates its color, brightness, and flexibility, and images of cyan, green, and red ‘Morpho butterflies’ created from photos of Morpho-mimetic thin films with corresponding colors.