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Ke Du, Junjun Ding, Ishan Wathuthanthri, Chang-Hwan Choi
It is challenging to hierarchically pattern high-aspect-ratio nanostructures on microstructures using conventional lithographic techniques, where photoresist film is not able to uniformly cover on the microstructures as the aspect ratio increases. Such non-uniformity causes poor definition of nanopatterns over the microstructures. Nanostencil lithography can provide an alternative means to hierarchically construct nanostructures on microstructures via direct deposition or plasma etching through a free-standing nanoporous membrane...
September 15, 2017: Nanotechnology
Hashim Alhmoud, Anna Cifuentes-Rius, Bahman Delalat, David G Lancaster, Nicolas H Voelcker
In order to address the issue of pathogenic bacterial colonization of diabetic wounds, a more direct and robust approach is required, which relies on a physical form of bacterial destruction in addition to the conventional biochemical approach (i.e. antibiotics). Targeted bacterial destruction through the use of photothermally active nanomaterials has recently come into the spotlight as a viable approach to solving the rising problem of antibiotic resistant microorganisms. Materials with high absorption coefficients in the near infrared (NIR) region of the electromagnetic spectrum show promise as alternative antibacterial therapeutic agents, since they preclude the development of bacterial resistance and can be activated on demand...
September 14, 2017: ACS Applied Materials & Interfaces
Longjian Xue, Belén Sanz, Aoyi Luo, Kevin T Turner, Xin Wang, Di Tan, Rui Zhang, Hang Du, Martin Steinhart, Carmen Mijangos, Markus Guttmann, Michael Kappl, Aránzazu Del Campo
Biological materials achieve directional reinforcement with oriented assemblies of anisotropic building blocks. One such example is the nanocomposite structure of keratinized epithelium on the toe pad of tree frogs, in which hexagonal arrays of (soft) epithelial cells are crossed by densely packed and oriented (hard) keratin nanofibrils. Here, a method is established to fabricate arrays of tree-frog-inspired composite micropatterns composed of polydimethylsiloxane (PDMS) micropillars embedded with polystyrene (PS) nanopillars...
September 8, 2017: ACS Nano
Lingyu Kong, Yi Song, Jeong Dong Kim, Lan Yu, Daniel Wasserman, Wai Kin Chim, Sing Yang Chiam, Xiuling Li
Producing densely packed high aspect ratio In0.53Ga0.47As nanostructures without surface damage is critical for beyond Si-CMOS nanoelectronics and optoelectronics devices. However, conventional dry etching methods are known to produce irreversible damage to III-As compound semiconductors because of the inherent high energy ion-driven process. In this work, we demonstrate the realization of ordered, uniform, array-based In0.53Ga0.47As pillars with diameters as small as 200 nm using the damage-free metal-assisted chemical etching (MacEtch) technology combined with the post-MacEtch digital etching smoothing...
September 7, 2017: ACS Nano
Mikhail Kryuchkov, Jannis Lehmann, Jakob Schaab, Vsevolod Cherepanov, Artem Blagodatski, Manfred Fiebig, Vladimir L Katanaev
Moth-eye nanostructures are a well-known example of biological antireflective surfaces formed by pseudoregular arrays of nipples and are often used as a template for biomimetic materials. Here, we provide morphological characterization of corneal nanostructures of moths from the Bombycidae family, including strains of domesticated Bombyx mori silk-moth, its wild ancestor Bombyx mandarina, and a more distantly related Apatelodes torrefacta. We find high diversification of the nanostructures and strong antireflective properties they provide...
September 6, 2017: Journal of Nanobiotechnology
Takahiro Koishi, Kenji Yasuoka, Xiao Cheng Zeng
Molecular dynamics simulations of impinging nanodroplets were performed to study the bounce back condition for flat and nanopillared surfaces. We found that the bounce back condition can be closely related to the degree of droplet deformation upon collision with the solid surface. When the droplets have little or small deformation, the bounce back condition solely depends on the hydrophobicity of the surface. On the other hand, when the droplet deformation is large, the impinging velocity dependence of the bounce back condition becomes stronger due to the increase of the liquid-vapor interfacial area of colliding droplet, which is proportional to the liquid-vapor surface energy...
September 6, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Ilknur Hatice Eryilmaz, John Mohanraj, Simone Dal Zilio, Alessandro Fraleoni-Morgera
Self-assembly methods allow to obtain ordered patterns on surfaces with exquisite precision, but often lack in effectiveness over large areas. Here we report on the realization of hierarchically ordered polymethylmethacrylate (PMMA) nanofibres and nanodots over large areas from solution via a fast, easy and low-cost method named ASB-SANS, based on a ternary solution that is cast on the substrate. Simple changes to the ternary solution composition allow to control the transition from nanofibres to nanodots, via a wide range of intermediate topologies...
September 5, 2017: Scientific Reports
Wook-Jae Lee, Hyunseok Kim, Jong-Bum You, Diana L Huffaker
Compact on-chip light sources lie at the heart of practical nanophotonic devices since chip-scale photonic circuits have been regarded as the next generation computing tools. In this work, we demonstrate room-temperature lasing in 7 × 7 InGaAs/InGaP core-shell nanopillar array photonic crystals with an ultracompact footprint of 2300 × 2300 nm(2), which are monolithically grown on silicon-on-insulator substrates. A strong lateral confinement is achieved by a photonic band-edge mode, which is leading to a strong light-matter interaction in the 7 × 7 nanopillar array, and by choosing an appropriate thickness of a silicon-on-insulator layer the band-edge mode can be trapped vertically in the nanopillars...
August 25, 2017: Scientific Reports
Nina Buch-Månson, Arnaud Spangenberg, Laura Piedad Chia Gomez, Jean-Pierre Malval, Olivier Soppera, Karen L Martinez
Mammalian cells have been widely shown to respond to nano- and microtopography that mimics the extracellular matrix. Synthetic nano- and micron-sized structures are therefore of great interest in the field of tissue engineering, where polymers are particularly attractive due to excellent biocompatibility and versatile fabrication methods. Ordered arrays of polymeric pillars provide a controlled topographical environment to study and manipulate cells, but processing methods are typically either optimized for the nano- or microscale...
August 23, 2017: Scientific Reports
Kuang-Yu Yang, Ruggero Verre, Jérémy Butet, Chen Yan, Tomasz J Antosiewicz, Mikael Käll, Olivier J F Martin
Electromagnetic metasurfaces with strong nonlinear responses and angular selectivity could offer many new avenues for designing ultrathin optics components. We investigated the optical second harmonic generation from plasmonic metasurfaces composed of aligned gold nanopillars with a pronounced out-of-plane tilt using a flexible nonlinear Fourier microscope. The experimental and computational results demonstrate that these samples function as wavevector-selective nonlinear metasurfaces, that is, the coherent second harmonic signal does not only depend on the polarization and wavelength of the excitation beam, but also of its direction of incidence, in spite of the subwavelength thickness of the active layer...
September 13, 2017: Nano Letters
Doyeon Bang, Eun-Jung Jo, SoonGweon Hong, Ju-Young Byun, Jae Young Lee, Min-Gon Kim, Luke P Lee
Frequency upconversion activated with Lanthanide has attracted attention in various real-world applications, because it is far simpler and more efficient than traditional nonlinear susceptibility-based frequency upconversion, such as second harmonic generation. However, the quantum yield of frequency upconversion of Lanthanide-based upconversion nanoparticles remains inefficient for practical applications, and spatial control of upconverted emission is not yet developed. To overcome this limitation, we developed asymmetric hetero-plasmonic nanoparticles (AHPNs) consisting of plasmonic antennae in nanocrescent shapes on the Lanthanide-based upconversion nanoparticle (UC) for efficiently delivering excitation light to the UC core by nanofocusing of light and generating asymmetric frequency upconverted emission concentrated toward the tip region...
August 21, 2017: Nano Letters
Heng Xie, Han-Xiong Huang, Yu-Jiang Peng
The fine nanostructure on the cicada wing of Cryptotympana atrata fabricius, which exhibits hydrophobicity and antireflectivity, is carefully examined. A promising strategy is proposed for facilely and successively replicating the natural functional nanostructure of the cicada wing onto polystyrene (PS) surfaces. First, a nickel replica with tapered nanopores is fabricated by combining electroless plating and subsequent electroplating with the natural cicada wing as an original template. Then, using microinjection compression molding, with the nickel replica as a template, the tapered nanopores are transcribed onto the PS surface, resulting in orderly and densely arranged nanopillars with a mean diameter of about 156 nm and a mean pitch of about 180 nm...
August 24, 2017: Nanoscale
Chaoran Liu, Jing Sun, Jing Li, Chenghao Xiang, Lufeng Che, Zuankai Wang, Xiaofeng Zhou
The directional and long-range droplet transportation is of great importance in microfluidic systems. However, it usually requires external energy input. Here we designed a wettability gradient surface that can drive droplet motion by structural topography. The surface has a wettability gradient range of over 150° from superhydrophobic to hydrophilic, which was achieved by etching silicon nanopillars and adjusting the area of hydrophilic silicon dioxide plane. We conducted force analysis to further reveal the mechanism for droplet self-propulsion, and found that the nanostructures are critical to providing a large driving force and small resistance force...
August 8, 2017: Scientific Reports
Aleksei Kabedev, Mark Ross-Lonergan, Vladimir Lobaskin
We study solute transport in a microfluidic channel, where the walls hold an array of tilted rigid nanopillars. By solving numerically the flow equations in the channel, we show that a combination of hydrodynamic effects with excluded volume interactions between the solute particles and the pillars leads to a hydrodynamic lift effect, which varies with the particle size, and depends in a strongly nonlinear fashion on the flow rate. We show that the lift force can be sufficiently strong to drive the solute accumulation or removal from the pillar region and can be switched to the opposite direction by variation of the shear rate or driving pressure...
July 28, 2017: Electrophoresis
Aron Hakonen, FengChao Wang, Per Ola Andersson, Håkan Wingfors, Tomas Rindzevicius, Michael Stenbæk Schmidt, Venugopal Rao Soma, Shicai Xu, YingQi Li, Anja Boisen, HengAn Wu
Picric acid (PA) is a severe environmental and security risk due to its unstable, toxic, and explosive properties. It is also challenging to detect in trace amounts and in situ because of its highly acidic and anionic character. Here, we assess sensing of PA under nonlaboratory conditions using surface-enhanced Raman scattering (SERS) silver nanopillar substrates and hand-held Raman spectroscopy equipment. The advancing elasto-capillarity effects are explained by molecular dynamics simulations. We obtain a SERS PA detection limit on the order of 20 ppt, corresponding attomole amounts, which together with the simple analysis methodology demonstrates that the presented approach is highly competitive for ultrasensitive analysis in the field...
February 24, 2017: ACS Sensors
Megan D Mulroe, Bernadeta R Srijanto, S Farzad Ahmadi, C Patrick Collier, Jonathan B Boreyko
It was recently discovered that condensation growing on a nanostructured superhydrophobic surface can spontaneously jump off the surface, triggered by naturally occurring coalescence events. Many reports have observed that droplets must grow to a size of order 10 μm before jumping is enabled upon coalescence; however, it remains unknown how the critical jumping size relates to the topography of the underlying nanostructure. Here, we characterize the dynamic behavior of condensation growing on six different superhydrophobic nanostructures, where the topography of the nanopillars was systematically varied...
August 22, 2017: ACS Nano
Liang Zhao, Huy Q Ta, Arezoo Dianat, Akash Soni, Artem Fediai, Wanjian Yin, Thomas Gemming, Barbara Trzebicka, Gianaurelio Cuniberti, Zhongfan Liu, Alicja Bachmatiuk, Mark H Rummeli
The promise of sp(2) nanomaterials remains immense, and ways to strategically combine and manipulate these nanostructures will further enhance their potential as well as advance nanotechnology as a whole. The scale of these structures requires precision at the atomic scale. In this sense electron microscopes are attractive as they offer both atomic imaging and a means to structurally modify structures. Here we show how Cr atoms can be used as physical linkers to connect carbon nanotubes and fullerenes to graphene...
July 12, 2017: Nano Letters
José Francisco Algorri, Braulio García-Cámara, Alexander Cuadrado, José Manuel Sánchez-Pena, Ricardo Vergaz
Dielectric metasurfaces based on high refractive index materials have been proposed recently. This type of structure has several advantages over their metallic counterparts. In this work, we demonstrate that dielectric metasurfaces can be theoretically designed satisfying Kerker's zero-forward condition. This is the first time that a dielectric metasurface based on this principle has been designed. A selective dielectric metasurface of silicon nanopillars is designed to work at 632.8 nm. This structure could work both as a dielectric mirror and a reject band filter...
July 7, 2017: Nanomaterials
Hidetaka Asoh, Ryota Imai, Hideki Hashimoto
GaAs nanopillar arrays were successfully fabricated by metal-assisted chemical etching using Au nanodot arrays. The nanodot arrays were formed on substrates by vacuum deposition through a porous alumina mask with an ordered array of openings. By using an etchant with a high acid concentration and low oxidant concentration at a relatively low temperature, the area surrounding the Au/GaAs interface could be etched selectively. Under the optimum conditions, Au-capped GaAs nanopillar arrays were formed with an ordered periodicity of 100 nm and pillar heights of 50 nm...
December 2017: Nanoscale Research Letters
Xiaoyin Sun, Takao Yasui, Takeshi Yanagida, Noritada Kaji, Sakon Rahong, Masaki Kanai, Kazuki Nagashima, Tomoji Kawai, Yoshinobu Baba
Here, we developed a device integrated with a nanochannel and nanostructures to slow DNA translocation velocity. We found that translocation velocity of a single DNA molecule inside a nanochannel was decreased by pre-elongating it using some nanostructures, such as a shallow channel or nanopillars. This decrease of the translocation velocity was associated with the DNA mobility change, which is an intrinsic parameter of DNA molecules and unaffected by an electric field.
2017: Analytical Sciences: the International Journal of the Japan Society for Analytical Chemistry
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