Patterning of spontaneous rolling thin polymer films for versatile microcapillaries

We investigate the spontaneous rolling of polydimethylsiloxane (PDMS) thin films and demonstrate the fabrication of capillaries with topographical and chemical patterns on the inner wall. Thin films of PDMS are either coated by a layer of hard material or have their surface hardened by plasma oxidation. They are then driven out of equilibrium by selective solvent swelling in vapor phase resulting in a tubular rolled‐up system. The inner diameter of those is measured as a function of layer thickness for different solvents and capping types. Those results are shown to be in good agreement with Timoshenko theory. Before rolling, the future inner surface can be characterized and functionalized. We demonstrate topographical and chemical patterning, respectively by embossing and microcontact printing. These methods are very simple and can easily produce cylindrical capillaries with inner diameter between 20 and some hundreds of microns with fully functionalized inner surface, overcoming many difficulties encountered in conventional soft lithography techniques. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55, 721–728     

Determination of electron affinity of carbonyl radicals by means of negative ion mass spectrometry

Appearance energies of [M-H](-) ions from carbonyl compounds R-CO-R' (R,R' = H, CH(3), NH(2), OH) have been measured by means of negative ion mass spectrometry in resonant electron capture mode. Values of electron affinity of the corresponding radicals, CH(2)&dbond;C(X)O, NH&dbond;C(X)O and O&dbond;C(X)O, have been determined. Copyright 1999 John Wiley & Sons, Ltd.     

The multi-functional aspect of scanning holographic microscopy: a review(Invited Paper)

Recent developments in scanning holographic microscopy that offer the prospects of new quantitative tools and imaging modalities in bio, micro, and nano sciences are reviewed. The versatility of the method is emphasized. Scanning holography can operate in an incoherent mode for fluorescence imaging, in a coherent mode for quantitative phase imaging, or in a tomographic mode for axial sectioning and rejection of the out-of-focus haze. Possible applications are illustrated with examples, and future prospects ...     

A Novel Fibrous Material Created by Self‐Rolling of a Patterned Polymer Thin Film

A new kind of a fibrous material is produced by controlled self‐rolling of patterned thin poly(4‐vinyl)pyridine films in acidic water. Self‐rolling is induced by unequal swelling of the top and the bottom layers of the films in the solvent. Rolling starts from parallel scratches in the film and results in twin‐scroll fibers. The fibers are stabilized by staining with CuCl₂ salt and freeze‐dried. The output of the fiber material production is of the order of 1 cm³ from approximately 50 cm² of the patterned polymer film. The approach opens new broad opportunities for creation of smart fibrous materials via loading the fibers with functional micro‐ and nanoparticles.     

Formation of self-rolled polymer microtubes studied by combinatorial approach

This paper describes an experimental study of the polymer microtube formation in different fabrication conditions. A photolithography route is demonstrated for the fabrication of large amount of uniform and good quality polymer microtubes. TEM grids were used as mask and exposure of UV radiation was done in two steps to create asymmetric patterns. The diameter of tube was controlled by regulating the thickness of polymer layers, UV radiation dose and concentration of acidic solution. The results indicate that thickness of the bilayer film was the most dominating factor to determine the tube’s dimension, and diameter of the tubes increased with increase in the thickness of bilayer. The kinetics of the tube formation was studied with respect to acidity of the solution and UV dose. Rate of rolling increased with the acidity of the solution. Tube diameter and rate of rolling decreased with the increase of the UV exposure time. Films with two-dimensional gradients of layer thicknesses were prepared to study a broad range of parameters in a single experiment. The tubes were characterized in detail using optical microscopy and scanning electron microscopy. These polymer microtubes have potential applications in microfluidic devices and biotechnology field.     

Primitive Illumination Systems for Families of Convex Bodies in the Plane

Let F= {C₁,C₂,...,C} be a family of ndisjoint convex bodies in the plane. We say that a set Vof exterior light sources illuminates F, if for every boundary point of any member of Fthere is a point in Vsuch that is visible from ,i.e. the open line segment joining and is disjoint from F. An illumination system Vis called primitive if no proper subset of Villuminates F. Let p_max(F) denote the maximum number of points forming a primitive illumination system for F, and letp_max(n) denote the minimum of F) taken over all families Fconsisting of ndisjoint convex bodies in the plane. The aim of this paper is to investigate the quantities p_max(F) and p_max(n).     

Spatial localization and dynamics of water molecules with good tetrahedral surroundings

The local structure of the molecular- dynamic model of water (729 particles at 300 K) is analyzed by isolating molecules whose surroundings differ slightly in configuration from a regular tetrahedron. These molecules are not randomly distributed in space but form nanometer clusters having a fractal structure. In these clusters, molecules are less mobile than the model molecules in general;their self- correlation function of rate and the density of vibrational states also differ from the average characteristics of the system. Translated fromZhumal Strukturnoi Khimii, Vol. 38, No. 4, pp. 713–722, July–August, 1997.     

Long-range interaction of picosecond solitons through excitation of acoustic waves in optical fibers

We present the theory of electrostrictional interaction of soliton pulses in optical fibers. Solitons excite acoustic waves propagating in the direction transverse to the fiber axis. Scattering of optical radiation on these waves leads to a timing jitter of the optical pulses arrival time. We consider this effect as nonlinear self-scattering of light on acoustic waves. Because of the fact that a value of acoustic lifetime can reach a value of about 100 ns self-scattering on acoustic waves can be observed for a single optical pulse as well as for an optical pulse sequence as a whole. The value of single soliton self-frequency shift due to excitation of acoustic waves as a function of soliton duration have been obtained. For soliton duration _sol > 14 ps an acoustic wave soliton self-frequency shift is larger than the Raman soliton self-frequency shift.The obtained theoretical results describe well the long-range interaction of soliton pulse trains in an optical fiber. The value of bit error rate due to electrostrictional interaction of optical pulses in high bit rate, ultra long soliton communication systems have been obtained.