1,721,041 research outputs found
Mesoscopic, templated self-assembly at the fluid-fluid interface
No full textThis paper demonstrates templated self-assembly-based on capillary forces-of millimeter-scale poly-(dimethylsiloxane) plates suspended at the water-perfluorodecalin interface. The system described abstracts the concept of "templating" from molecular templating and uses it to design millimeter-scale aggregates that self-assemble in ordered structures. This work points the way to new strategies for organizing complex, millimeter-scale structures
Mesoscale folding: A physical realization of an abstract, 2D lattice model for molecular folding
No full textElectric winds driven by time oscillating corona discharges
No full textWe investigate the formation of steady gas flows-so-called electric winds-created by point-plane corona discharges driven by time oscillating (ac) electric fields. By varying the magnitude and frequency of the applied field, we identify two distinct scaling regimes: (i) a low frequency (dc) regime and (ii) a high frequency (ac) regime. These experimental observations are reproduced and explained by a theoretical model describing the transport and recombination of ions surrounding the discharge and their contribution to the measured wind velocity. The two regimes differ in the spatial distribution of ions and in the process by which ions are consumed. Interestingly, we find that ac corona discharges generate strong electric forces localized near the tip of the point electrode, while dc corona discharges generate weaker forces distributed throughout the interelectrode region. Consequently, the velocity of the electric winds (>1 m/s) generated by ac discharges is largely independent of the position of the counter electrode. The unified theoretical description of dc and ac electric winds presented here reconciles previous observations of winds driven by dc corona and ac dielectric barrier discharges; insights from the model should also prove useful in the design of other plasma actuators. (C) 2013 AIP Publishing LLC
Observation of diastereomers of the hydrogen-bonded aggregate Hub(M)(3)center dot 3CA using H-1 nuclear magnetic resonance spectroscopy when CA is an optically-active isocyanuric acid
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Molecule-mimetic chemistry and mesoscale self-assembly
No full textMolecules are structured aggregates of atoms joined by chemical bonds; crystals are aggregates of molecules, interacting covalently or noncovalently. The work described in this Account uses molecules, crystals, and other forms of atomic/molecular matter to suggest principles that can be used in generating structured aggregates df millimeter-scale components, interacting through capillary interactions. The properties of these aggregates-that is, their "chemistry"-mimic aspects of the chemistry of molecules
Mesoscale self-assembly of hexagonal plates using lateral capillary forces: Synthesis using the "capillary bond
No full textThis paper examines self-assembly in a quasi-two-dimensional, mesoscale system. The system studied here involves hexagonal plates ("hexagons") of poly(dimethylsiloxane) (PDMS; 5.4 mm in diameter, 0.9-2.0 mm thick), with faces functionalized to be hydrophilic or hydrophobic, floating at the interface between perfluorodecalin (PFD) and H(2)O. The hexagons assemble by capillary forces originating in the interactions of the menisci at their hydrophobic and hydrophilic rectangular faces. The strength and directionality of the interactions can be tailored by manipulating the heights of the faces, the pattern of the hydrophobic faces, the pattern of hydrophobic regions on these faces, and the densities of the three interacting phases (organic Liquid, aqueous liquid, polymeric solid). Examination of all 14 possible combinations of hydrophobic and hydrophilic faces on the hexagonal plates led to three outcomes: (i) the extension of the strategies of self-assembly from the molecular to the mesoscale, (ii) the demonstration of a system in which small objects can be designed to self-assemble into a variety of arrays, and (iii) the hypothesis that capillary forces between objects can, in some circumstances, be considered to form the basis for a "bond" between them-the capillary bond-and be used in synthesis in a way analogous to that in which noncovalent bonds are employed in molecular-scale synthesis
Self-assembly of hydrogen-bonded polymeric rods based on the cyanuric acid center dot melamine lattice
No full textThis paper describes the self-assembly of hydrogen-bonded polymeric rods based on the lattice of cyanuric acid and melamine (CA . M). Data from H-1 NMR spectroscopy, IR spectroscopy, gel permeation chromatography (GPC), and transmission electron microscopy (TEM) are interpreted as indicating that the self-assembly of a bisisocyanuric acid (bisCA) and a bismelamine (bisM) formed polymeric nanorods [(bisCA)(n)(bisM)(n)] composed of parallel CA . M rosettes. The TEM results suggest that these rods aggregate as bundles. The length of the bundles ranged from 100 to 1500 nm, and their diameter was in the range from 15 to 500 nm
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