Parameter optimization and structural design of polymer arrayed waveguide grating multiplexer

First some important parameters are optimized for the structural design of a polymer arrayed waveguide grating (AWG) multiplexer around the central wavelength of 1.55 μm with the wavelength spacing of 1.6 nm. These parameters include the thickness and width of the guide core, mode effective refractive indices and group refractive index, diffraction order, pitch of adjacent waveguides, length difference of adjacent arrayed waveguides, focal length of slab waveguides, free spectral range (FSR), the number of input/output (I/O) channels, and that of arrayed waveguides. Then the bent angles, radii and lengths of all the input/output channels and arrayed waveguides are determined. Finally, a schematic waveguide layout of this device is presented, which contains 2 slabs, 11 input channels, 11 output channels, and 91 arrayed waveguides.     

A molecular dynamics study of ion migration in a doped electroactive polymer

Simulating the \hbox{BF}_{4}^{-} -doped poly(3-octylthiophene) lattice by molecular dynamics results in a structure in which dopant ions intercalate as a sandwich between thiophene rings on adjacent polymer chains. The ions occupy sites in channels parallel to the polymer main chain, which retains a high degree of planarity in contrast to the pristine (undoped) polymer. Even when lattice imperfections are created by expanding the cell, Coulomb forces ensure that the intercalation features containing the dopant channels are largely retained. On applying electric fields in the principal directions of the 'perfect lattice' it is found that the ions migrate most readily along the ion-channel directions (the lattice c axis), leaving the lattice undisturbed. Although higher electric fields cause dopant migration to occur perpendicular to the channel directions they destroy the intercalated lattice. In the reduced-order lattice regions substantial motion of the ions are predicted at a critical value of the lattice parameter.     

PVDF–PEO/ZSM-5 based composite microporous polymer electrolyte with novel pore configuration and ionic conductivity

A novel composite microporous polymer electrolyte based on poly(vinylidene fluoride), poly(ethylene oxide), and microporous molecular sieves ZSM-5 (denoted as PVDF–PEO/ZSM-5) was prepared by a simple phase inversion technique. PEO can obviously improve the pore configuration, such as pore size, porosity, and pore connectivity of PVDF-based microporous membranes, results in a high room temperature ionic conductivity. Microporous molecular sieves ZSM-5 can further improve the mechanical strength of PVDF–PEO blends and form special conducting pathway in PVDF–PEO matrix by absorb liquid electrolyte in its two-dimensional interconnect channels. The high room temperature ionic conductivity combined with good mechanical strength implies that PVDF–PEO/ZSM-5 based composite microporous polymer electrolyte can be used as candidate electrolyte and/or separator material for high-performance rechargeable lithium batteries.     

Multifunctional spectrum-periodic polymer MZI electro-optic switch/filter using serial-cascaded phase-generating couplers: theory, design and analysis

A multifunctional polymer asymmetric Mach-Zehnder interferometer electro-optic switch/filter comprising two serial-cascaded phase-generating couplers and a pair of microstrip electrodes is proposed. Due to the optimization on PGC structure with the given nonlinear least square approximation method, the phase compensation condition and extinction ratio (ER) compensation condition are both realized for achieving periodic frequency response. The ON- and OFF-states voltages are 0 and 8.06 V, respectively. The device has two input ports (A1 and B1) and two output ports (A2 and B2), port A2 contains 10 channels numbered from #?7 to #2, and port B2 contains 9 channels numbered from #?7 to #1. As an optical filter (ON-state), the wavelength space of each channel is within 19.2–21?nm (standard value 20?nm) with the maximum period variation less than 1?nm. The insertion loss for channels #?7 to #2 of port A2 is within 2.69–19.3 dB, and that for channels #?7 to #1 of port B2 is within 2.09–20.2 dB. As an EO switch, the ER of each channel between ON-state and OFF-state for port A2 is more than 15.7 dB, and that for port B2 is more than 12.6 dB. Besides, as required in CWDM networks, the device also exhibits favorable thermal stability under the case of large temperature variation.     

The impact of point thermal absorbers in ablation of poly(methyl methacrylate)

Molecular dynamics (MD) simulations are used to study the interactions of photons with a poly(methyl methacrylate), or PMMA, substrate and point thermal absorbers. The point thermal absorbers are embedded within the polymer matrix which can be excited and transfer energy to the surrounding particles through an internal vibrational mode. Using a fluence above the ablation threshold, two excitation channels are studied—one includes a direct heating of the polymer and the other includes the excitation of the thermal absorbers. Although the yield of ejected particles is similar for both simulations, the plume composition differs. For the simulation of the excitation of the point thermal absorbers, the plume consists of a greater number of smaller substrate fragments due to local high temperature regions.     

Hybrid femtosecond laser microfabrication to achieve true 3D glass/polymer composite biochips with multiscale features and high performance: the concept of ship‐in‐a‐bottle biochip

True three‐dimensionally (3D) integrated biochips are crucial for realizing high performance biochemical analysis and cell engineering, which remain ultimate challenges. In this paper, a new method termed hybrid femtosecond laser microfabrication which consists of successive subtractive (femtosecond laser‐assisted wet etching of glass) and additive (two‐photon polymerization of polymer) 3D microprocessing was proposed for realizing 3D “ship‐in‐a‐bottle” microchip. Such novel microchips were fabricated by integrating various 3D polymer micro/nanostructures into flexible 3D glass microfluidic channels. The high quality of microchips was ensured by quantitatively investigating the experimental processes containing “line‐to‐line” scanning mode, improved annealing temperature (645°C), increased prebaking time (18 h for 1mm‐length channel), optimal laser power (1.9 times larger than that on the surface) and longer developing time (6 times larger). The ship‐in‐a‐bottle biochips show high capabilities to provide simultaneous filtering and mixing with 87% efficiency in a shorter distance and on‐chip synthesis of ZnO microflower particles.     

Dielectric properties of the P(VDF<Subscript>60</Subscript>/Tr<Subscript>40</Subscript>) copolymer in the porous glass matrix

The dielectric properties and electrical conductivity of the composite material, which was prepared by incorporating the P(VDF₆₀/Tr₄₀) copolymer into the porous glass matrix (the average pore diameter is approximately equal to 320 nm), and the bulk sample of the P(VDF₆₀/Tr₄₀) copolymer have been investigated in the temperature range 290–440 K. It is revealed that the incorporated material is characterized by an increase in the melting temperature and a considerable decrease in the temperature at which the ferroelectric phase formed in polymer inclusions becomes unstable. It is shown that charge transfer in the composite material occurs predominantly through channels filled with the polymer.     

Switching effects in composite films based on the conjugated polymer polyfluorene and ZnO nanoparticles

The S- and N-shaped current—voltage characteristics have been studied for composite films of the conjugated polymer polyfluorene and ZnO nanoparticles deposited onto Al and In₂O₃/SnO₂ electrodes with and without an intermediate sublayer of the conducting polymer PEDT/PSS. The differences in the current— voltage characteristics of the systems (the N- and S-types, respectively) are interpreted using the electro-thermal switching model, which takes into account the structural and electric properties of PEDT/PSS. The switching provides both alignment of polymer molecules and tunneling of charge carriers, which leads to an increase in conductivity. The current flow in this structure causes an increase in temperature of conducting channels; when the temperature reaches certain levels, the conductivity of the channels decreases because the alignment of polymer molecules is upset, which creates an N-shaped form of the current—voltage characteristics.     

Electron transport in self-assembled polymer molecular junctions

A molecular junction of a poly(p-phenyleneethynylene)s derivative with thioacetate end groups (TA-PPE) was fabricated by self-assembling. Nanogap electrodes made by electroplating technique was used to couple thiol end groups of TA-PPE molecules. Room temperature current-voltage characteristics of the molecular junction exhibited highly periodic, repeatable, and identical stepwise features. First-principles calculations suggest that one possibility for the equidistant step is due to the opening of different conducting channels that corresponds to the unoccupied molecular orbitals of the polymer in the junction. It is interesting to see that an 18 nm long polymer is of quantized electronic structures and behaves like a quantum transport device.     

Field extraction of ions from liquid solutions with the use of polymer track membranes

The general principles of the electric field assisted ion evaporation in the membrane ion source are considered. In the ion source, the liquid sample under investigation is placed in narrow channels of a polymer track membrane, which separates the liquid sample at atmospheric pressure from the vacuum chamber. Stability of the liquid at strong electric fields is provided by a choice of the diameters of channels and the liquid–polymer contact angle. The electric charge on the vacuum–polymer interface is of great importance for creation of the strong electric field near the liquid–vacuum interface. Such a conclusion is made from the computations of the electric field in the framework of the model developed. The mechanism of the electric field assisted evaporation of ions is discussed to explain the observed mass spectra for the ions extracted from liquid.     

Elementary excitations in nanochannel arrays of quantum wires

We present an analytical model for the Coulomb interaction effects in quantum wires forming a nanochannel array. We study the elementary excitations (plasmons and electron-hole excitations) of electron arrays forming three-dimensional structures. The plasmon spectrum of boson arrays is also calculated. Our model applies to bulk material with one-dimensional conduction channels as realized in organic or polymer crystals and in nanochannel array glasses.     

The a-c field influence on conductive channels formation in thread-like structure polymers

The conductive channels formation and disappearance probability is investigated for thin films of thread-like structure polymers in the a-c field. Depending on the field strength and frequency and the channel orientation in the field the soliton solutions were obtained as well as the oscillatory solutions for the conductive state propagation along the polymer molecule. The field dependence of the rate of polymer film dielectric-metal switching is found.     

Theoretical study on adsorption properties of methyl methacrylate and its molecular chain within metal‐organic frameworks

Utilizing metal‐organic frameworks (MOFs) as a “polymerization container” is a very effective method to prepare oriented and therefore birefringent polymer materials. In particular, the adsorption of polymer monomers and molecular chains within MOFs has a profound impact on the orientation of polymer chains. In this work, a theoretical study on the adsorption properties of methyl methacrylate (MMA) and its molecular chain within MOFs has been conducted by employing a combination of molecular dynamics, density functional theory, and Monte Carlo method, where 2 MOFs, [Zn₂(1,4‐benzenedicarboxylate)₂triethylenediamine]_n and [Zn₂(4,4′‐biphenyldicarboxylate)₂triethylenediamine]_n, were chosen. The corresponding number and degree of orientation of adsorbed molecules in these 2 MOFs were obtained from the simulations. The calculation results revealed 3 factors that affect the adsorption and orientation of MMA monomers in MOF pore channels. First, as the walls of the MOF pores are polar surfaces and consist of metal ions and organic ligands, the electrostatic interaction between the MOF channels and polar MMA molecules promotes the adsorption and orientation of the MMA monomers within the pore channel. Second, the electrostatic interactions between monomers can reduce the intermolecular gaps, which similarly assist in their orientation. Last, the relative sizes of the MOF pores and the monomers are also relevant. When the sizes of the MOF channels and monomers are similar, the molecular chains show a higher degree of orientation. The results and the findings of this work could provide predictive methods for selecting polymeric monomers or MOFs that may be ideal for the control of polymer chain orientation.     

Effect of excessive pressure on the drift mobility of charge carriers in poly(diphenylene phthalide) films

The electron-hole transport in poly(diphenylene phthalide) films has been investigated. The dependence of the drift mobility of charge carriers on the excessive mechanical pressure has been studied using the time-of-flight method. It has been revealed that, with an increase in the thickness of the polymer film, the dispersive transport of charge carries gives way to the quasi-dispersive transport. In thin films in the prethreshold range (i.e., before switching of the samples to the highly conductive state under excessive pressure), the electron mobility increases and exceeds the hole mobility. The experimental results have been discussed in the framework of the model describing the transport through the channels formed by metastable electron-hole pairs.     

Anodic aluminium oxide: Concurrent SEM and SANS characterisation. Influence of AAO confinement on PEO mean-square displacement

Anodic aluminium oxide (AAO) membranes are macroscopically highly ordered systems made of oriented nano-scale parallel cylindrical channels. The membrane topology is defined by the pore radius, the inter-pores distance and the pore length. We show by a combined SANS and SEM study that the membrane morphology can be tailored by the main anodization parameters: voltage, temperature and anodization duration. We show that the confinement of an hydrophilic polymer (poly(ethylene oxide)) inside the pores is possible. We observe a striking effect of the confinement on the polymer mean-square displacement as measure by high resolution neutron quasi-elastic scattering.     

Theory of transport of long polymer molecules through carbon nanotube channels

A theory of transport of long chain polymer molecules through carbon nanotube (CNT) channels is developed using the Fokker-Planck equation and direct molecular dynamics simulations. The mean transport or translocation time tau is found to depend on the chemical potential energy, the entropy, and the diffusion coefficient. A power law dependence tau approximately N2 is found, where N is the number of monomers in a molecule. For 10(5)-unit long polyethylene molecules, tau is estimated to be approximately 1 micros. The diffusion coefficient of long polymer molecules inside CNTs, like that of short ones, is found to be a few orders of magnitude larger than in ordinary silicate based zeolite systems.     

毛细微模塑法制作聚合物微球的有序结构

用毛细微模塑法在玻璃基片上组装了聚苯乙烯微球紧密的有序阵列 .扫描电镜观察了组装后的微球排列 .结果表明 ,在毛细通道的出口端 ,聚苯乙烯的微球堆积得紧密有序 .毛细通道的尺寸 ,环境温度和聚合物微球乳液的浓度是毛细微模塑法的主要影响因素 .     

Multi-channel light modulation based on the attenuation total reflection

Multi-channel light modulation, which is based on the attenuated total reflection (ATR) configuration, is proposed in this paper. The device consists of a prism and a polymer optical waveguide. Guided modes which give rise to the resonance dips in the ATR spectrum are employed to act as the modulation channels. Double channel's modulation with the same modulation signal has been demonstrated in the proposed device.     

Electrochemical control of surface wettability of poly(3-alkylthiophenes)

The effect of n-alkyl side-chain length on water contact angle with films in neutral and electrochemically doped states are studied. Increasing the side-chain from butyl to hexyl to octyl increases the contact angle of water on conjugated polymer films in both electrochemical states, but decreases the difference in angle between the states in the same film. Devices based on these films have potential application in, for example, guiding water and other liquids through microfluidic channels in lab-on-a-chip and micro-electro-mechanical (MEM) applications.