Magnetic field‐induced alignment of polybenzimidazole microstructures to enhance proton conduction

Aligned polymer microstructures in the field of biomaterials, semiconductors, and ion‐conductive membranes expand steadily. Here, an alternative aligned polybenzimidazole (WM PBI) microstructures fabrication strategy based on the utilization of a weak magnetic field (0.3 T) via the solvent casting method is demonstrated. The anisotropic alignment is induced by the interaction of the π‐electron‐rich structure with the magnetic field. A ripple‐like structure was observed in the field‐emission scanning electron microscopy image for the WM PBI membrane, which depicted the successful alignment of the PBI structure toward magnetic field direction. Electrochemical studies revealed the bulk resistance of WM PBI with only 13.71 × 10³ Ω compared to the unaligned PBI (WOM PBI) (63.01 × 10³ Ω). WM PBI marked as the highest proton conductivity of 610.66 × 10^?6 S cm^?1, and it was proven that the external magnetic field does bring the impact toward the augmentation of the proton conductivity, which is useful in various future generation applications.     

Bi‐directional ACET micropump for on‐chip biological applications

The ability to control and pump high ionic strength fluids inside microchannels forms a major advantage for clinical diagnostics and drug screening processes, where high conductive biological and physiological buffers are used. Despite the known potential of AC electro‐thermal (ACET) effect in different biomedical applications, comparatively little is known about controlling the velocity and direction of fluid inside the chip. Here, we proposed to discretize the conventional electrodes to form various asymmetric electrode structures in order to control the fluid direction by simple switching the appropriate electric potential applied to the discretized electrodes. The ACET pumping effect was numerically studied by solving electrical, thermal and hydrodynamic multi‐physic coupled equations to optimize the geometrical dimensions of the discretized system. PBS solutions with different ionic strength were seeded with 1 μm sized fluorescent particles and electrothermally driven fluid motion was observed inside the channel for different electrode structures. Experimental analyses confirm that the proposed micropump is efficient for a conductivity range between 0.1 and 1 S/m and the efficiency improves by increasing the voltage amplitude. Behavior of the proposed electrode–electrolyte system is discussed by lumped circuit model. Frequency response of system illustrated that the optimal frequency range increases by increasing the conductivity of medium. For 0.18 S/m PBS solution, the constant pumping effect was observed at frequency range between 100 kHz and 1 MHz, while frequency range of 100 kHz to 5 MHZ was observed for 0.42 S/m. The characteristics of experimental results were in good agreement with the theoretical model.     

银包玻珠核壳复合粒子的表面处理及环氧导电胶的电性能

以化学还原法合成的银包玻珠核壳复合粒子(Ag/GM)为原料, 乙二胺为表面处理剂, 制备了表面吸附有乙二胺的Ag/GM, 并用它作为导电填料组成了导电胶. 与化学还原法直接合成或沸水处理的Ag/GM相比, 乙二胺处理的Ag/GM能更有效地分散在环氧树脂胶黏剂中, 且能与环氧树脂基体产生化学键合, 降低Ag/GM和环氧树脂基体间的界面能, 用其制备的导电胶的导电率较高, 导电渗滤阈值较低. 同时, 结合导电网络理论和等效电路图, 阐明了用乙二胺处理的Ag/GM作填料制备的导电胶具有较低体积电阻率的原因.     

金属-有机框架衍生的多功能光催化剂

在光催化过程中,光催化剂被太阳能激发产生光生电子和空穴,来实现环境净化或能量转换,是应对全球变暖和能源短缺的有效途径之一.然而,光催化技术面临的主要瓶颈问题是光生载流子的低分离效率和高反应能垒.而催化剂本身的特性对这一点起到了决定性的作用.因此,催化剂的合理设计和改性是提高光催化效率的关键.金属有机框架(MOFs)是一...     

Electro‐conductive double‐network hydrogels

Novel electro‐conductive and mechanically‐tough double network polymer hydrogels (E‐DN gels) were synthesized by polymerization of 3, 4‐ethylenedioxythiophene in the presence of a double network hydrogel (DN gel) matrix. The E‐DN gels showed not only excellent mechanical performance, having a fracture stress of 1.4–2.1 MPa, but also electrical conductivity as high as 10^?3 S cm^?1, both under dry and water‐swollen states. The fracture stress and fracture energy of the E‐DN gel was increased by 1.7 and 3.4 times, respectively, as compared with the DN gel. From scanning electron microscope and AFM observations, it was found that electro‐conductive poly(3,4‐ethylenedioxythiophene) (PEDOT) was incorporated into DN gel matrix, apparently due to the formation of a poly‐ion complex with sulfonic acid group of the DN gel network. Thus, PEDOT incorporated into the DN gel matrix greatly improves not only electronic conductivity, but also mechanical properties, reinforcing the double network gel matrix. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012     

Electrical circuits from capillary flow driven evaporation deposition of carbon nanotube ink in non-porous V-grooves

Low cost pliable electronics portend the advancement of novel inexpensive microfluidic electrochemical devices. In the direct printing approach, the manner of deposition of conductive material from a liquid suspension to ensure electrical continuity is crucial. We describe here an approach in which V-groove networks that make up the path of circuitry are first scribed on non-porous inexpensive surfaces. Liquid drops of carbon nanotube ink are then placed on the surface adjacent to the V-grooves to enable wicking to produce the electrical circuit. This method essentially bypasses the need for inkjet printing. We investigate the basic efficacy of the conductive networks developed using this approach and demonstrate its use in generating electrically driven liquid flow of particles in a simple open capillary channel.     

Experimental verification of an equivalent circuit for the characterization of electrothermal micropumps: High pumping velocities induced by the external inductance at driving voltages below 5 V

Electrothermal micropumps (ETμPs) use local heating to create conductivity and permittivity gradients in the pump medium. In the presence of such gradients, an external AC electric field influences smeared spatial charges in the bulk of the medium. When there is also a symmetry break, the field‐charge interaction results in an effective volumetric force resulting in medium pumping. The advantages of the ETμP principle are the absence of moving parts, the opportunity to passivate all the pump structures, homogeneous pump‐channel cross‐sections, as well as force plateaus in broad frequency ranges. The ETμPs consisted of a DC‐heating element and AC field electrodes arranged in a 1000 μm × 250 μm × 60 μm (length × width × height) channel. They were processed as platinum structures on glass carriers. An equivalent‐circuit diagram allowed us to model the frequency‐dependent pumping velocities of passivated and nonpassivated ETμPs, which were measured at medium conductivities up to 1.0 S/m in the 300 kHz to 52 MHz frequency range. The temperature distributions within the pumps were controlled by thermochromic beads. Under resonance conditions, an additional inductance induced a tenfold pump‐velocity increase to more than 50 μm/s at driving voltages of 5 V_rms. A further miniaturization of the pumps is viewed as quite feasible.     

Rapid electrothermal response and excellent flame retardancy of ethylene‐vinyl acetate electrothermal film

In this study, high electrical conductivity and flame retardant electrothermal ethylene‐vinyl acetate (EVA) films were fabricated by using carbon nanotubes‐wrapped ammonium polyphosphate (CAPP) and conductive carbon black (CCB). CAPP was used as a synergistic conductive filler and flame retardant to improve the electrical conductivity and fire safety of the electrothermal film at the same time. Besides, the heat release rate (HRR) and the total heat release (THR) of EVA‐5 decreased about 81.5% and 57.3% compared with those of pure EVA film, respectively. Moreover, by incorporating a small amount of CAPP, EVA‐5 can reach up to V‐0 rating with an limiting oxygen index (LOI) value of 31%. EVA film fabricated by CCB and CAPP as conductive material exhibited almost 10 times increment on electrical conductivity than that of same content for CCB alone. And time vs temperature profiles of EVA‐5 showed a stable trend over 3600 seconds without any offset at a given applied voltage of 15 V. Moreover, its excellent cycle heating performance indicated that the electrothermal film can be recycled, which meets the requirements of sustainable development. In a word, this novel strategy provides a simple and effective way to obtain a high conductive and fire safety electrothermal film.     

A novel particle separation method based on induced‐charge electro‐osmotic flow and polarizability of dielectric particles

A new microfluidic method of particle separation was proposed and studied theoretically in this paper. This method is based on the induced charge electro‐osmotic flow (ICEOF) and polarizability of dielectric particles. In this method, a pair of metal plates is embedded on the side channel walls to create a region of circulating flows under applied electric field. When a dielectric particle enters this region, the vortices produced by ICEOF around the particle will interact with the circulating flows produced by the metal plates. Such hydrodynamic interaction influences the particle's trajectory, and may result in the particle being trapped in the flow circulating zone or passing through this flow circulating zone. Because the hydrodynamic interaction is sensitive to the applied electric field, and the polarizability and the size of the particles, separation of different particles can be realized by controlling these parameters. Comparing with electrophoresis and dielectrophoresis methods, this strategy presented in this paper is simple and sensitive.     

Improving Elasticity of Conductive Silicone Rubber by Hollow Carbon Black

Carbon black-based conductive rubber composites have important impacts on electromagnetic interference(EMI) shielding applications. However, an excessive amount of carbon black in the recipes of these conductive rubbers has caused their weak elasticity. Herein, hollow carbon black(HCB) particles were used to tune the elasticity of conductive rubber composites. Unique hollow morphology produced a better compression recovery of HCB than other solid carbon black, such as acetylene black. When the coupling agent was bonded to HCB, their conductive silicone rubber composites were featured by high stretching resilience, a fast compression recovery and excellent conductivity to satisfy the electromagnetic interference shielding requirements. Importantly, the rubber composites with coupling HCB had extremely low variations of mechanical property, conductivity and EMI shielding effectiveness after thermal accelerated aging tests. It is therefore revealed that the elasticity of HCB and its interfacial chemical coupling with rubber chains both play crucial roles in adjusting the elasticity of conductive rubber to sever long-term EMI protection.     

Investigation of Electrical Conductivity Properties and Electro Transport of a Novel Multi Walled Carbon Nanotube Electro Membrane under Constant Current

This study used multi‐walled carbon nanotube in electro‐membrane extraction studies under direct constant current for the first time for the electro transport of cypermethrin (CYP) from aqueous to acceptor phase. A novel and developed membrane exhibits visible and remarkable recovery values (82.76 %) for the removal of CYP under 0.3 A constant current at 60 V in 30 minutes. It is demonstrated that regenerating electro membrane by multi‐walled carbon nanotubes (MWCNTs) increased the electrical conductivity, thermal Ea values of a novel membrane (750 meV) and stability, and it resulted in better and higher kinetic results on the transport process. This study presents a potential solution for the limited use of electro‐membrane extraction at higher current values. Regenerating of the electro membrane by MWCNTs not only allows us to work even at high current values, it prevents the formation of electrolysis up to a certain current value in donor and acceptor phases. Thermogravimetric analysis of the novel membrane also confirms successful regeneration of the electro membrane by MWCNTs. Electro‐membrane extraction studies have gained a new perspective and innovation by the use of MWCNTs in electro‐membrane process.     

Effect of conductive particles on the mechanical,electrical, and thermal properties of maleated polyethylene

Inclusion of conductive particles is a convenient way for the enhancement of electrical and thermal conductivities of polymers. However, improvement of the mechanical properties of such composites has remained a challenge. In this work, maleated polyethylene is proposed as a novel matrix for the production of conductive metal–thermoplastic composites with enhanced mechanical properties. The effects of two conductive particles (iron and aluminum) on the morphological, mechanical, electrical, and thermal properties of maleated polyethylene were investigated. Morphological observations revealed that the matrix had excellent adhesion with both metal particles. Increase in particle concentration was shown to improve the tensile strength and modulus of the matrix significantly with iron being slightly more effective. Through‐plane electrical conductivity of maleated polyethylene was also substantially improved after adding iron particles, while percolation was observed at particle contents of around 20–30% vol. In the case of aluminum, no percolation was observed for particle contents of up to 50% vol., which was linked to the orientation of the particles in the in‐plane direction due to the squeezing flow. Inclusion of particles led to substantial increase (over 700%) in the thermal conductivities of both composites. The addition of high concentrations of metal particles to matrix led to the creation of two groups of materials: (i) composites with high electrical and thermal conductivities and (ii) composites with low electrical and high thermal conductivities. Such characteristics of the composites are expected to provide a unique opportunity for applications where a thermally conductive/electrically insulating material is desired. Copyright © 2015 John Wiley & Sons, Ltd.     

Emulsion synthesis of nanoparticles containing PEDOT using conducting polymeric surfactant: Synergy for colloid stability and intercalation doping

Poly(3,4‐ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT:PSS) is a widely used conductive aqueous dispersion synthesized by using emulsion polymerization method. To further enhance its solution processability and conductivity of PEDOT derivatives, we proposed to replace the nonconductive PSS with conductive poly[2‐(3thienyl)‐ethoxy‐4‐butylsulfonate] (PTEB) as surfactant for the emulsion polymerization of PEDOT. The reaction involved colloid stabilization and doping in one step, and yielded PEDOT:PTEB composite nanoparticles with high electrical conductivity. Contrary to its counterpart containing nonconductive surfactant, PEDOT: PTEB showed increasing film conductivity with increasing PTEB concentration. The result demonstrates the formation of efficient electrical conduction network formed by the fully conductive latex nanoparticles. The addition of PTEB for EDOT polymerization significantly reduced the size of composite particles, formed stable spherical particles, enhanced thermal stability, crystallinity, and conductivity of PEDOT:PTEB composite. Evidence from UV–VIS and FTIR measurement showed that strong molecular interaction between PTEB and PEDOT resulted in the doping of PEDOT chains. X‐ray analysis further demonstrated that PTEB chains were intercalated in the layered crystal structure of PEDOT. The emulsion polymerization of EDOT using conducting surfactant, PTEB demonstrated the synergistic effect of PTEB on colloid stability and intercalation doping of PEDOT during polymerization resulting in significant conductivity improvement of PEDOT composite nanoparticles. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2536–2548, 2008     

Novel conductive nanocomposites from perfluoropolyether waterborne polyurethanes and carbon nanotubes

The exceptional electrical conductivity of carbon nanotubes (CNTs) has been exploited for the preparation of conductive nanocomposites based on a large variety of insulating polymers. Among these, perfluoropolyether‐polyurethanes (PFPE‐PUs) represent a class of highly performing fluorinated materials with excellent water/oil repellency, chemical resistance, and substrate adhesion. The incorporation of highly conductive fillers to this class of highly performing materials allows them to be exploited in new technological and industrial fields where their unique properties need to be combined with the electrical conductivity or the electrostatic dissipation properties of carbon nanotubes. However, no studies have been presented so far on nanocomposites based on PFPE‐PUs and CNTs. In this work, polymer nanocomposites based on waterborne PFPE‐PUs and increasing amounts of carboxylated multiwall CNTs (COOH‐CNTs) were prepared and characterized for the first time. The effect of increasing concentration of COOH‐CNTs on the physical, mechanical, and surface properties of the nanocomposites was investigated by means of rheological measurements, dynamic mechanical analysis, thermal characterization, optical contact angle measurements, and scanning electron microscopy. In addition, electrical measurements showed that the highly insulating undoped PFPE‐PU system undergoes substantial modifications upon addition of COOH‐CNTs, leading to the formation of conductive nanocomposites with electrical conductivities as high as 1 S/cm. The results of this study demonstrate that the addition of COOH‐CNTs to PFPE‐PU systems represents a promising strategy to expand their possible use to technological applications where chemical stability, water/oil repellence and electrical conductivity are simultaneously required. Copyright © 2014 John Wiley & Sons, Ltd.     

Designable Guest-Molecule Encapsulation in Metal–Organic Frameworks for Proton Conductivity

Metal–organic frameworks (MOFs), as a porous frame material, exhibit considerable electrical conductivity. In recent decades, research on the proton conductivity of MOFs has made gratifying progress. In this review, the designable guest molecules encapsulated into MOFs are summarized and generalized into four types in terms of promoting proton conductive performance, and then recent progress in the promotion of proton conductivity by MOFs encapsulating guest molecules is discussed. The existing challenges and prospects for the development of this strategy for promoting MOFs’ proton conductivity are also listed.     

Morphology of polyethylene–carbon black composites

Carbon black is a common polymer additive that is used for reinforcement and for its ability to enhance physical properties, such as conductivity. This article pertains to an X‐ray scattering (SAXS) study of a conductive grade of carbon black and carbon black–polymer composites. The scattering pattern for such blacks displays a surface‐fractal‐like power‐law decay over many decades in scattering vector q. It is often assumed that small‐angle scattering from carbon black aggregates can be described in terms of surface‐fractal models, related to particles with fractally rough surfaces. Such self‐similar surface roughness is usually easy to identify by microscopy; however, electron microscopy from these blacks fails to support this assumption. It is proposed here that this apparent surface‐fractal scattering actually represents a more complicated morphology, including overlapping structural features and a power‐law scaling of polydispersity. One use of conductive black–polyethylene composites is in circuit protection devices where resistive heating leads to a reversible association of carbon black aggregates that controls switching between a conductive and a nonconductive state. Scattering can be used as an in situ tool to observe the morphological signature of this reversible structural change. Scattering patterns support a model for this switching based on local enhancement of concentration and the formation of linear agglomerates associated with the matrix polymer's semicrystalline morphology. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 1105–1119, 1999     

Electrical and optical properties of ceramic–polymer nanocomposite coatings

Transparent, conductive composite coatings were fabricated from suspensions of poly(vinyl acetate‐acrylic) (PVAc‐co‐acrylic) copolymer latices (50–600 nm) and nanosized antimony‐doped tin oxide (ATO) particles (～15 nm). The suspensions were deposited as coatings onto poly(ethylene terephthalate) substrates and dried at 50 °C. Microstructure studies using field emission scanning electron microscopy and tapping‐mode atomic force microscopy (TMAFM) indicated that the latex particles coalesced during drying and forced the ATO particles to segregate into the boundaries between the latex particles. Low phase contrast was observed with TMAFM; this result was consistent with the presence of PVAc‐co‐acrylic in the ATO‐rich phase of the composite. The conductivity of the composite coatings followed a percolation power‐law equation, with the percolation threshold between 0.05 and 0.075 volume fractions of ATO and the critical conductivity exponent ranging from 1.34 to 2.32. The highest direct‐current conductivity of the composite coatings was around 10^?2 S/cm. The optical transmittance and scattering behavior of the coatings were also investigated. Compared with the PVAc‐co‐acrylic coating, the composite coatings had lower transparency because of the Rayleigh scattering. The transparency of the composite coatings was improved by a reduction in the coating thickness. The best transparency for the coatings with a direct‐current conductivity of approximately 10^?2 S/cm was around 85% at a wavelength of 600 nm. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 1744–1761, 2003     

Structured elastomeric submillimeter films displaying magneto and piezo resistivity

Structured elastomer films (100–150 µm) presenting piezo and magneto resistance are described. The films are composites of filler particles, which are both electrically conductive and magnetic, dispersed in an elastomeric matrix. The particles consist of magnetite (6 nm) grouped in silver‐coated aggregates (Fe₃O₄@Ag). The matrix is styrene–butadiene rubber (SBR) in which diethylene glycol (DEG) is added. The particles, SBR and DEG, are dispersed in toluene and then placed between two rare earth magnets. Formation of pseudo‐chains (needles) of inorganic material aligned in the direction of the magnetic field is obtained after solvent evaporation. The addition of DEG is substantial to obtain an electrically conductive material. The electrical conductivity is anisotropic and increases when applying normal stresses and/or magnetic fields in the direction of the needles. The elastomers, particles, and needless were characterized by XRD, SEM, EDS, FTIR, DSC, TGA, VSM, profilometry, and stress–strain analysis. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 574–586     

Coupling Photocatalysis and Redox Biocatalysis Toward Biocatalyzed Artificial Photosynthesis

In green plants, solar‐energy utilization is accomplished through a cascade of photoinduced electron transfer, which remains a target model for realizing artificial photosynthesis. We introduce the concept of biocatalyzed artificial photosynthesis through coupling redox biocatalysis with photocatalysis to mimic natural photosynthesis based on visible‐light‐driven regeneration of enzyme cofactors. Key design principles for reaction components, such as electron donors, photosensitizers, and electron mediators, are described for artificial photosynthesis involving biocatalytic assemblies. Recent research outcomes that serve as a proof of the concept are summarized and current issues are discussed to provide a future perspective.     

On‐chip pressure generation using a gel membrane fabricated outside of the microfluidic network

On‐chip generation of pressure gradients via electrokinetic means can offer several advantages to microfluidic assay design and operation in a variety of applications. In this article, we describe a simple approach to realizing this capability by employing a polyacrylamide‐based gel structure fabricated within a fluid reservoir located at the terminating end of a microchannel. Application of an electric field across this membrane has been shown to block a majority of the electroosmotic flow generated within the open duct yielding a high pressure at the channel–membrane junction. Experiments show the realization of higher pressure‐driven velocities in an electric field‐free separation channel integrated to the micropump with this design compared to other similar micropumps described in the literature. In addition, the noted velocity was found to be less sensitive to the extent of Debye layer overlap in the channel network, and therefore more impressive when working with background electrolytes having higher ionic strengths. With the current system, pressure‐driven velocities up to 3.6 mm/s were realized in a 300‐nm‐deep separation channel applying a maximum voltage of 3 kV at a channel terminal. To demonstrate the separative performance of our device, a nanofluidic pressure‐driven ion‐chromatographic analysis was subsequently implemented that relied on the slower migration of cationic analytes relative to the neutral and anionic ones in the separation channel likely due to their strong electrostatic interaction with the channel surface charges. A mixture of amino acids was thus separated with resolutions greater than those reported by our group for a similar analysis previously.