The fabrication of a hemispherical electronic-eye camera with optimized designs based upon micromechanical analysis is reported. The photodetector arrays combine layouts with multidevice tiles and extended, non-coplanar interconnects to improve the fill factor and deformability, respectively. Quantitative comparison to micromechanics analysis reveals the key features of these designs. Color images collected with working cameras demonstrate the utility of these approaches.
The self-assembly of molecularly precise nanostructures is widely expected to form the basis of future high-speed integrated circuits, but the technologies suitable for such circuits are not well understood. In this work, DNA self-assembly is used to create molecular logic circuits that can selectively identify specific biomolecules in solution by encoding the optical response of near-field coupled arrangements of chromophores. The resulting circuits can detect label-free, femtomole quantities of multiple proteins, DNA oligomers, and small fragments of RNA in solution via ensemble optical measurements. This method, which is capable of creating multiple logic-gate-sensor pairs on a 2 × 80 × 80-nm DNA grid, is a step toward more sophisticated nanoscale logic circuits capable of interfacing computers with biological processes.
Millimeter-sized reactor particles made of permeable polymer doped with catalysts arranged in a core/shell fashion direct sequences of chemical reactions (e.g., alkyne coupling followed by hydrogenation or hydrosilylation followed by hydrogenation). Spatial compartmentalization of catalysts coupled with the diffusion of substrates controls reaction order and avoids formation of byproducts. The experimentally observed yields of reaction sequences are reproduced by a theoretical model, which accounts for the reaction kinetics and the diffusion of the species involved.
Iron oxide nanoparticle internalization exerts detrimental effects on cell physiology for a variety of particles, but little is known about the mechanism involved. The effects of high intracellular levels of four types of iron oxide particles (Resovist, Endorem, very small organic particles, and magneto-liposomes (MLs)) on the viability and physiology of murine C17.2 neural progenitor cells and human blood outgrowth endothelial cells are reported. The particles diminish cellular proliferation and affect the actin cytoskeleton andmicrotubule network architectures as well as focal adhesion formation and maturation. The extent of the effects correlates with the intracellular concentration (= iron mass) of the particles, with the biggest effects for Resovist and MLs at the highest concentration (1000 μg Fe mL~(-1)). Similarly, the expression of focal adhesion kinase (FAK) and the amount of activated kinase (pY397-FAK) are affected. The data suggest that high levels of perinuclear localized iron oxide nanoparticles diminish the efficiency of protein expression and sterically hinder the mature actin fibers, and could have detrimental effects on cell migration and differentiation.
The organized incorporation of novel biocompatible organic nanostructures into extremely sensitive amperometric biosensors is demonstrated. The high sensitivity reported, together with the biocompatibility and the ability to chemically and biologically modify these elements, may provide a novel platform for biosensor design and fabrication for environmental monitoring, homeland security, and other applications.
A capillary steady microjet produced at the discharge region of a gas jet expanding into vacuum is imaged using scanning electron microscopy. The co-flowing gas focuses by inertia and pulls the liquid fed through a capillary tube concentrically positioned at the discharge orifice. The jet breaks up into well-collimated droplets. Numerical simulation explains the persistence of the liquid phase after discharge into vacuum.
Empty (devoid of RNA) viruslike particles (eVLPs) of Cowpea mosaic virus can now be obtained readily. CPMV can encapsulate, within the protein capsid, cobalt or iron oxide by environmentally benign processes. The external surface also remains amenable to chemical modification. The development of eVLPs for targeted delivery of therapeutic agents is now a reality.
Gold nanocages represent a new class of nanomaterials with compact size and tunable optical properties in the near-infrared region. They passively accumulate in the tumor after intravenous injection. By exposing tumors to a near-infrared diode laser, the photothermal effect of the Au nanocages selectively destroys tumor tissue with minimum damage to the surrounding healthy tissue.
A method for fabricating gel-immobilized colloidal crystal spheres using microfluidics is reported. The diffraction color or photonic wavelength of the gelimmobilized colloidal crystal spheres can be adjusted by varying the particle concentration before gelation and tuned by external stimuli after preparation.
Despite the fact that we live in a 3D world and macroscale engineering is 3D, conventional submillimeter-scale engineering is inherently 2D. New fabrication and patterning strategies are needed to enable truly 3D-engineered structures at small size scales. Here, strategies that have been developed over the past two decades that seek to enable such millimeter to nanoscale 3D fabrication and patterning are reviewed. A focus is the strategy of self-assembly, specifically in a biologically inspired, more deterministic form, known as self-folding. Self-folding methods can leverage the strengths of lithography to enable the construction of precisely patterned 3D structures and "smart" components. This self-assembly approach is compared with other 3D fabrication paradigms, and its advantages and disadvantages are discussed.
Thermally driven self-assembly of nanomicelles can be a feasible route to produce monodisperse porous colloidal nanocomposites of inorganic nature and sizes around the mesoscale (below 100 nm). Success relies on extending the lifetime of intermediate droplets (size below about 100 nm) that are obtained under particular conditions. Herein, the conditions for the long-term stabilization of these unique templates are studied and a model proposed to produce monodisperse porous colloidal nanocomposites. As an example of the potential applications of this methodology, functional colloidal nanocomposites with a high loading of the doping material (30 mol%) are obtained. In particular, superparamagnetic nanomagnets of metallic nature encapsulated in porous oxide colloidal matrixes of mesoscale size that easily respond to an external magnetic field are prepared and characterized in terms of structure and textural and magnetic properties.
Poly(3,4-ethylenedioxythiophene) (PEDT) is recognized as one of the most promising conducting polymers for future applications in the fields of electronics, optics, energy storage/conversion, and biomedical science. The toxicity of PEDT could be considered to affect the potential for its widespread application. Herein, the cytotoxicity and proinflammatory response of PEDT nanomaterials of three different shapes toward human lung fibroblast (IM R90) and mouse alveolar macrophage (J774A.1) cells are investigated. The shape-dependent toxicity of the PEDT nanomaterials is evaluated by examining cell morphological change, cytotoxicity, apoptosis/necrosis, oxidative stress, and immune response. The cytotoxicity and apoptosis of the nanomaterials increase with their decreasing aspect ratio in both cell lines. The formation of reactive oxygen species in cells treated with PEDT nanomaterials is dependent on the shape and concentration of the nanomaterial. Proinflammatory cytokines, such as interleukin-1, interleukin-6, and tumor necrosis factor α from macrophages, are induced by PEDT nanomaterial-treated cells.
A method is demonstrated to prepare graphene dispersions at high concentrations, up to 1.2mg mL~(-1), with yields of up to 4 wt% monolayers. This process relies on low-power sonication for long times, up to 460 h. Transmission electron microscopy shows the sonication to reduce the flake size, with flake dimensions scaling as t~(-1/2). However, the mean flake length remains above 1 μm for all sonication times studied. Raman spectroscopy shows defects are introduced by the sonication process. However, detailed analysis suggests that predominately edge, rather than basal-plane, defects are introduced. These dispersions are used to prepare high-quality freestanding graphene films. The dispersions can be heavily diluted by water without sedimentation or aggregation. This method facilitates graphene processing for a range of applications.
A stoichiometric derivative of graphene with a fluorine atom attached to each carbon is reported. Raman, optical, structural, micromechanical, and transport studies show that the material is qualitatively different from the known graphene-based nonstoichiometric derivatives. Fluorographene is a high-quality insulator (resistivity >10(12) Omega) with an optical gap of 3 eV. It inherits the mechanical strength of graphene, exhibiting a Young's modulus of 100 N m(-1) and sustaining strains of 15%. Fluorographene is inert and stable up to 400 degrees C even in air, similar to Teflon.
A two-phase method is exploited to prepare many kinds of nearly monodisperse, highly crystalline, size- and shape-controlled, surface-property-tunable inorganic nanocrystals, such as metal, semiconducting, magnetic, dielectric, and rare earth nanocrystals. The reaction of the two-phase system happens at the interface between the oil (nonpolar) and water (polar) phases and the interface is an exclusive site for both nucleation and growth. Interestingly, many solvent pairs with a clear interface can be applied to synthesize inorganic nanocrystals successfully. Generally, as-prepared nanocrystals with organic ligands are soluble in nonpolar solvents. Furthermore, exchange of ligands can also be realized readily and the final nanocrystals can be soluble in polar solvents. This two-phase method is a simple, reproducible, and general route and is becoming as powerful an approach as other solution-based synthetic approaches to high-quality inorganic nanocrystals.
The high-molar-extinction-coefficient heteroleptic ruthenium aye, cis-Ru (4,4'-bis(5-octylthieno3,2-b] thiophen-2-yl)-2,2'-bipyridine) (4,4'-dicarboxyl-2,2'-bipyridine) (NCS)(2), exhibits an AM 1.5 solar (100 mW cm(-2))-to-electric power-conversion efficiency of 4.6% in a solid-state dye-sensitized solar cell (SSDSC) with 2,2', 7,7'-tetrakis-(N,N-di-p-methoxyphenylamine,)9,9'-spirobifluorene (spiro-MeOTAD) as the organic hole-transporting material. These SSDSC devices exhibit good durability during accelerated tests under visible-light soaking for 1000 h at 60 degrees C. This demonstration elucidates a class of photovoltaic devices with potential for stable and low-cost power generation. The electron recombination dynamics and charge collection that take place at the dye-sensitized heterojunction are studied by means of impedance and transient photovoltage decay techniques.