Perpendicular Magnetization and Generic Realization of the Ising Model in Artiﬁcial Spin Ice

PRL 109, 087201 (2012)

We have studied frustrated kagome arrays and unfrustrated honeycomb arrays of magnetostatically
interacting single-domain ferromagnetic islands with magnetization normal to the plane. The measured
pairwise spin correlations of both lattices can be reproduced by models based solely on nearest-neighbor
correlations. The kagome array has qualitatively different magnetostatics but identical lattice topology to
previously studied artiﬁcial spin ice systems composed of in-plane moments. The two systems show
striking similarities in the development of moment pair correlations, demonstrating a universality in
artiﬁcial spin ice behavior independent of speciﬁc realization in a particular material system

Department of Physics and Materials Research Institute, Pennsylvania State University, University Park, Pennsylvania 16802, USA
2
Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, Minnesota 55455, USA
3
Theoretical Division and Center for Nonlinear Studies, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
(Received 19 March 2012; published 21 August 2012)

Self made Origami structures

Self-Organized Origami Structures via Ion-Induced Plastic Strain

Khattiya Chalapat , * Nikolai Chekurov , Hua Jiang , Jian Li , Babak Parviz ,
and G. S. Paraoanu

Movement and deformation due to stress relaxation occurs in a variety of natural or artiﬁ cially-induced processes. In nature, some plants have evolved their organs as movable origami to
increase their reproductive success. In ice plants, the opening of the seed capsule is caused by a water-actuated strain mechanism. After the rain, the cells are full of water, causing the
expansion along the lid axis, and eventually the opening of the seed capsule. Similar to the ice plant seeds, various other objects move and deform through stress relaxation, ranging from
curling of ﬂ owers, self-organization at nanometer scale, to deformation of plasmid DNA in bacteria.

New technique for nanostructure assembly

Self-Assembled Colloidal Superparticles from Nanorods

Science 19 October 2012:
Vol. 338 no. 6105 pp. 358-363
DOI: 10.1126/science.1224221

Colloidal superparticles are nanoparticle assemblies in the form of colloidal particles. The assembly of nanoscopic objects into mesoscopic or macroscopic complex architectures allows bottom-up fabrication of functional materials. We report that the self-assembly of cadmium selenide–cadmium sulfide (CdSe-CdS) core-shell semiconductor nanorods, mediated by shape and structural anisotropy, produces mesoscopic colloidal superparticles having multiple well-defined supercrystalline domains. Moreover, functionality-based anisotropic interactions between these CdSe-CdS nanorods can be kinetically introduced during the self-assembly and, in turn, yield single-domain, needle-like superparticles with parallel alignment of constituent nanorods. Unidirectional patterning of these mesoscopic needle-like superparticles gives rise to the lateral alignment of CdSe-CdS nanorods into macroscopic, uniform, freestanding polymer films that exhibit strong photoluminescence with a striking anisotropy, enabling their use as downconversion phosphors to create polarized light-emitting diodes.

Nanometre optical coatings based on strong interference effects in highly absorbing media

Nature Materials

(2012)

doi:10.1038/nmat3443

Received: 20 June 2012
Accepted: 31 August 2012
Published online: 14 October 2012

Optical coatings, which consist of one or more films of dielectric or metallic materials, are widely used in applications ranging from mirrors to eyeglasses and photography lenses^1,2. Many conventional dielectric coatings rely on Fabry–Perot-type interference, involving multiple optical passes through transparent layers with thicknesses of the order of the wavelength to achieve functionalities such as anti-reflection, high-reflection and dichroism. Highly absorbing dielectrics are typically not used because it is generally accepted that light propagation through such media destroys interference effects. We show that under appropriate conditions interference can instead persist in ultrathin, highly absorbing films of a few to tens of nanometres in thickness, and demonstrate a new type of optical coating comprising such a film on a metallic substrate, which selectively absorbs various frequency ranges of the incident light. These coatings have a low sensitivity to the angle of incidence and require minimal amounts of absorbing material that can be as thin as 5–20 nm for visible light. This technology has the potential for a variety of applications from ultrathin photodetectors and solar cells to optical filters, to labelling, and even the visual arts and jewellery.

Enzymatic Sculpting of Nanoscale and Microscale Surface Topographies

Angewandte Chemie International Edition

Volume 51, Issue 38,pages 9619–9623,September 17, 2012

Lithography-free etching of complex surface features is achieved by harnessing the enzyme proteinase K (PK), controlled by bovine serum albumin (BSA), to digest a biodegradable polymer. This bio-sculpting process is used to construct a membraneless filtration device for the size-based isolation and enrichment of cells from whole blood.

Continuous Evolution Profiles for Electronic-Tongue-Based Analysis†

Dr. Yanxia Hou^1,*,
Maria Genua¹,
Dr. Dayane Tada Batista¹,
Dr. Roberto Calemczuk¹,
Dr. Arnaud Buhot¹,
Pauline Fornarelli²,
Dr. Jamal Koubachi²,
Prof. David Bonnaffé^2,*,
Els Saesen³,
Dr. Cédric Laguri³,
Dr. Hugues Lortat-Jacob³,
Dr. Thierry Livache^1,*

Article first published online: 11 SEP 2012

Licking the problem: A new type of electronic tongue was constructed by self-assembly on the surface of a surface plasmon resonance (SPR) imaging prism with combinations of simple building blocks. The resulting combinatorial array was used to detect proteins in solution (see scheme) using SPR imaging to monitor the interactions. The signal from each spot was dependent on its composition and the protein infused, and correlated with the response of its neighbors.

Direct-Write Patterning of Bacterial Cells by Dip-Pen Nanolithography

Jieun Kim, Young-Hun Shin, Seong-Hun Yun, Dong-Sik Choi, Ji-Hye Nam, Sung Ryong Kim, Sung-Kwon Moon, Bong Hyun Chung, Jae-Hyuck Lee, Jae-Ho Kim, Ki-Young Kim, Kyung-Min Kim, and Jung-Hyurk Lim

Publication Date (Web): September 19, 2012 (Communication)

DOI: 10.1021/ja3073808

J. Am. Chem. Soc., Article ASAP

DOI: 10.1021/ja3073808

Publication Date (Web): September 19, 2012

The ability of dip-pen nanolithography (DPN) to generate nano- or microarrays of soft or hard materials (e.g., small molecules, DNA, proteins, nanoparticles, sols, and polymers) in a direct-write manner has been widely demonstrated. The transporting of large-sized ink materials such as bacteria, however, remains a significant challenge with this technique. The size limitation of the water meniscus formed between the DPN tip and the solid surface becomes a bottleneck in such diffusion-based molecular transport experiments. Herein, we report a straightforward “stamp-on” DPN method that uses a nanostructured poly(2-methyl-2-oxazoline) hydrogel-coated tip and carrier agents to generate patterns of micrometer-sizedEscherichia coli JM 109 bacterial cells. We demonstrate that this approach enables the deposition of a single bacterial cell array on a solid surface or arrays of layers of multiple cells by modulating the viscosity of the “ink” solution. Fluorescence microscopy images indicated that the deposited bacterial cells were kept alive on Luria–Bertani-agar layered solid surfaces after DPN patterning.