The influence of electrolyte concentration on nanofractures fabricated in a 3D-printed microfluidic device by controlled dielectric breakdown

A three-dimensional-printed microfluidic device made of a thermoplastic material was used to study the creation of molecular filters by controlled dielectric breakdown. The device was made from acrylonitrile butadiene styrene by a fused deposition modeling three-dimensional printer and consisted of two V-shaped sample compartments separated by 750 µm of extruded plastic gap. Nanofractures were formed in the thin piece of acrylonitrile butadiene styrene by controlled dielectric breakdown by application voltage of 15–20 kV with the voltage terminated when reaching a defined current threshold. Variation of the size of the nanofractures was achieved by both variation of the current threshold and by variation of the ionic strength of the electrolyte used for breakdown. Electrophoretic transport of two proteins, R-phycoerythrin (RPE; <10 nm in size) and fluorescamine-labeled BSA (f-BSA; 2–4 nm), was used to monitor the size and transport properties of the nanofractures. Using 1 mM phosphate buffer, both RPE and f-BSA passed through the nanofractures when the current threshold was set to 25 µA. However, when the threshold was lowered to 10 µA or lower, RPE was restricted from moving through the nanofractures. When we increased the electrolyte concentration during breakdown from 1 to 10 mM phosphate buffer, BSA passed but RPE was blocked when the threshold was equal to, or lower than, 25 µA. This demonstrates that nanofracture size (pore area) is directly related to the breakdown current threshold but inversely related to the concentration of the electrolyte used for the breakdown process.     

Ag Nanoparticle-Incorporated Natural Rubber for Mechanical Energy Harvesting Application

The energy conversion performance of the triboelectric nanogenerator (TENG) is a function of triboelectric charges which depend on the intrinsic properties of materials to hold charges or the dielectric properties of triboelectric materials. In this work, Ag nanoparticles were synthesized and used to incorporate into natural rubber (NR) in order to enhance the dielectric constant for enhancing the electrical output of TENG. It was found that the size of Ag nanoparticles was reduced with the increasing CTAB concentration. Furthermore, the CTAB surfactant helped the dispersion of metallic Ag nanoparticles in the NR-insulating matrix, which promoted interfacial polarization that affected the dielectric properties of the NR composite. Ag nanoparticle-incorporated NR films exhibited an improved dielectric constant of up to almost 40% and an enhanced TENG performance that generated the highest power density of 262.4 mW/m².     

Dielectric and magnetic permittivities of three new ceramic tungstates MPr2W2O10 (M = Cd,Co, Mn)

Broadband dielectric spectroscopy measurements revealed an anomalously large relative permittivity value (ε _r?=?884) for MnPr₂W₂O₁₀, a smaller value (ε _r?=?156) for CoPr₂W₂O₁₀ and the smallest value (ε _r?=?22) for CdPr₂W₂O₁₀ at low frequency (ν?=?0.1?Hz) and above room temperature in the insulating and paramagnetic state. Below 273?K, the relative permittivity (ε _r?～?24) did not depend significantly on frequency for all the tungstates under study. Electrical resistivity, thermoelectric power, electron paramagnetic resonance, magnetic susceptibility and magnetization provided experimental evidence that the studies tungstates were paramagnetic insulators with low n-type conduction. Only in the case of MnPr₂W₂O₁₀ was a ferrimagnetic order below 45?K observed. These effects are discussed within the framework of Maxwell–Wagner polarization, chemical covalent bonds and porosity mechanism.     

On Quantitative Autoradiography of Semiconductor Basic Material

It will be described methods of the quantitative evaluation of elements interesting in semiconductor technology and their distribution in silicon using autoradiographic techniques. The local concentration of the element phosphorus in dependence of their local distribution is determined with silver halide films. As standard samples silicon disks phosphorus diffused are used.

The distribution of the element boron and their local concentration is determined on the way of neutron induced autoradiography (NIAR). In this technique boron implanted or diffused silicon disks are used as standard samples. Different possibilities of the quantitative evaluation of autoradiograms will be considered and compared.     

Macroscopic properties and their temperature dependence of the mesogen 4 cyano-4/-n-nonyl biphenyl as a function of temperature

The thermal dependence of optical and dielectric properties of one member namely 4 cyano-4^/-n-nonyl biphenyl (code name 9CB) of the mesogenic homologous series of 4 cyano-4^/-n-alkyl biphenyl (nCBs) is reported. The variation of orientational order parameter with temperature is determined and comparison made with theoretical Maier–Saupe values as well as the order parameter values of the other member of the series. The effect of temperature on the effective molecular dipole moment μ and the angle of inclination β of the dipole axis with the preferred direction are investigated.     

Alpha Spectrometry by Using CN85 Plastic Track Detectors

In the present study the alpha particle response which is characteristic of cellulose nitrate detectors CN85 was investigated The track diameter as a function of alpha energy was examined. With regard to the spectroscopy of alpha from track radii it was stated that the discrimination of lower alpha energies shows better results than the high energies for the present etching condition.     

Synthesis of multiwalled carbon nanotube/fluorine‐containing poly(p‐phenylene benzoxazole) composites exhibiting greatly enhanced dielectric constants

A series of high‐performance polymer/carbon nanotube (CNT) composites with different nanotube contents have been prepared via condensation of N‐silylated diamino terminated precursor of the polymer with acid chloride‐functionalized CNTs and subsequent thermal cyclodehydration. The composites have been fully characterized by infrared and Raman spectroscopy, electron microscopy, and thermal analysis. Various interesting morphologic features including helical structures have been observed in the composites as a result of covalent attachment of the polymer. The composites exhibit excellent thermal stability and a significant improvement in the dielectric constant and mechanical strength with the inclusion of CNTs. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Investigation of the viscoelastic properties of 4-propoxy-biphenyl-4-carbonitrile

ABSTRACT

We report on the temperature-dependent measurements of dielectric permittivity, birefringence, elastic constants and rotational viscosity for 4-propoxy-biphenyl-4-carbonitrile in the nematic region. The temperature dependence of the three elastic constants was determined from studies of the Freédericksz transition. The thermal dependence of elastic constants shows features similar to the literature (bend > splay > twist). Elastic constants are proportional to the square of the order parameter. Temperature-dependent dielectric characterisation was carried out at a frequency of 10 kHz. The compound shows positive dielectric anisotropy in the nematic phase. The rotational viscosity is found to be relatively low. Temperature dependence of order parameter is estimated using Haller’s method. The figure of merit was also calculated as a function of temperature.     

弛豫铁电体介电可调性的研究

无铅弛豫铁电体具有较好的介电可调性,在顺电相有较大的介电常数和极小的损耗,因较大的优值而被广泛地用于微波器件.根据现有的介电可调性理论,通过参量的适当修正,对介电可调性的表达式做了合理的探讨,结论适用于处理实验结果.比较发现,在电场作用下顺电相保持不变的近似得出的结论与实验结果差距较大,而转化为铁电相与实验结果完全吻合.考虑外加电场和自发极化对弹性吉布斯自由能的修正,导出了高电场对介电常数的修正关系,与实验结果相符.提出了介电可调度的概念与计算公式,能够定量表示掺杂对介电可调性的影响.