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RISS 인기검색어
- 검색키워드
- 저자 : Chaikin, P. M. (검색결과 3 건)
- 무료
- 기관 내 무료
- 유료
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Optimized Structures for Photonic Quasicrystals
Rechtsman, Mikael C.,Jeong, Hyeong-Chai,Chaikin, Paul M.,Torquato, Salvatore,Steinhardt, Paul J. American Physical Society 2008 Physical review letters Vol.101 No.7
<P>A photonic quasicrystal consists of two or more dielectric materials arranged in a quasiperiodic pattern with noncrystallographic symmetry that has a photonic band gap. We use a novel method to find the pattern with the widest TM-polarized gap for two-component materials. Patterns are obtained by computing a finite sum of density waves, assigning regions where the sum exceeds a threshold to a material with one dielectric constant, epsilon1, and all other regions to another, epsilon0. Compared to optimized crystals, optimized quasicrystals have larger gaps at low constrasts epsilon1/epsilon0 and have gaps that are much more isotropic for all contrasts. For high contrasts, optimized hexagonal crystals have the largest gaps.</P>
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Large-Area Nanosquare Arrays from Shear-Aligned Block Copolymer Thin Films
Kim, So Youn,Nunns, Adam,Gwyther, Jessica,Davis, Raleigh L.,Manners, Ian,Chaikin, Paul M.,Register, Richard A. American Chemical Society 2014 NANO LETTERS Vol.14 No.10
<P>While block copolymer lithography has been broadly applied as a bottom-up patterning technique, only a few nanopattern symmetries, such as hexagonally packed dots or parallel stripes, can be produced by spontaneous self-assembly of simple diblock copolymers; even a simple square packing has heretofore required more intricate macromolecular architectures or nanoscale substrate prepatterning. In this study, we demonstrate that square, rectangular, and rhombic arrays can be created via shear-alignment of distinct layers of cylinder-forming block copolymers, coupled with cross-linking of the layers using ultraviolet light. Furthermore, these block copolymer arrays can in turn be used as templates to fabricate dense, substrate-supported arrays of nanostructures comprising a wide variety of elements: deep (>50 nm) nanowells, nanoposts, and thin metal nanodots (3 nm thick, 35 nm pitch) are all demonstrated.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/nalefd/2014/nalefd.2014.14.issue-10/nl502416b/production/images/medium/nl-2014-02416b_0007.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nl502416b'>ACS Electronic Supporting Info</A></P>
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Light-activated self-propelled colloids
Palacci, J.,Sacanna, S.,Kim, S.-H.,Yi, G.-R.,Pine, D. J.,Chaikin, P. M. Royal Society 2014 Philosophical transactions. Series A, Mathematical Vol.372 No.2029
<P>Light-activated self-propelled colloids are synthesized and their active motion is studied using optical microscopy. We propose a versatile route using different photoactive materials, and demonstrate a multiwavelength activation and propulsion. Thanks to the photoelectrochemical properties of two semiconductor materials (α-Fe<SUB>2</SUB>O<SUB>3</SUB> and TiO<SUB>2</SUB>), a light with an energy higher than the bandgap triggers the reaction of decomposition of hydrogen peroxide and produces a chemical cloud around the particle. It induces a phoretic attraction with neighbouring colloids as well as an osmotic self-propulsion of the particle on the substrate. We use these mechanisms to form colloidal cargos as well as self-propelled particles where the light-activated component is embedded into a dielectric sphere. The particles are self-propelled along a direction otherwise randomized by thermal fluctuations, and exhibit a persistent random walk. For sufficient surface density, the particles spontaneously form ‘living crystals’ which are mobile, break apart and reform. Steering the particle with an external magnetic field, we show that the formation of the dense phase results from the collisions heads-on of the particles. This effect is intrinsically non-equilibrium and a novel principle of organization for systems without detailed balance. Engineering families of particles self-propelled by different wavelength demonstrate a good understanding of both the physics and the chemistry behind the system and points to a general route for designing new families of self-propelled particles.</P>
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