Electrorheologically intelligent polyaniline and its composites

Preparation of a novel magnetorheological fluid for high temperatures

Magnetorheological fluids, especially those in high-power magnetorheological devices, inevitably work at high temperatures because of the wall slip, energized coils and frictions between particles. In order to prepare a magnetorheological fluid for high temperatures, this work investigates the properties of three main components (soft magnetic particles, surfactants and base carrier fluids) for a magnetorheological fluid at high temperatures. On this basis, a novel magnetorheological fluid for high temperatures is prepared. Its sedimentation stability, viscosity and shear yield stress are investigated at high temperatures. The results show that the novel magnetorheological fluid has acceptable sedimentation, suitable viscosity and stable shear yield stress at high temperatures. The novel magnetorheological fluid for high temperatures can be applied to most magnetorheological devices, especially high-power magnetorheological devices.

Progress in Conductive Polyaniline-Based Nanocomposites for Biomedical Applications: A Review

Inherently conducting polymers (ICPs) are a specific category of synthetic polymers with distinctive electro-optic properties, which involve conjugated chains with alternating single and double bonds. Polyaniline (PANI), as one of the most well-known ICPs, has outstanding potential applications in biomedicine because of its high electrical conductivity and biocompatibility caused by its hydrophilic nature, low-toxicity, good environmental stability, and nanostructured morphology. Some of the limitations in the use of PANI, such as its low processability and degradability, can be overcome by the preparation of its blends and nanocomposites with various (bio)polymers and nanomaterials, respectively. This review describes the state-of-the-art of biological activities and applications of conductive PANI-based nanocomposites in the biomedical fields, such as antimicrobial therapy, drug delivery, biosensors, nerve regeneration, and tissue engineering. The latest progresses in the biomedical applications of PANI-based nanocomposites are reviewed to provide a background for future research.

Facile fabrication of core/shell structured SiO2/polypyrrole nanoparticles with surface modification and their electrorheology

We synthesized conductive polypyrrole (PPy) coated silica core–shell structured nanoparticles, and investigated their electrorheological (ER) characteristics under electric fields applied when dispersed in silicone oil.

Electrorheological response of inorganic-coated multi-wall carbon nanotubes with core-shell nanostructure

The effect of coating thickness and sequence on the multi-wall carbon nanotube (MWCNT) surface on electrorheological (ER) activity is investigated. Silica-coated MWCNTs with different shell thicknesses and inorganic-coated MWCNTs with different shell sequences are fabricated using the sol-gel process. The morphology and elemental analyses of the core-shell structured MWCNTs were performed and the effect of coating thickness and coating materials on the MWCNT surface on ER and dielectric properties of inorganic-coated MWCNT suspensions have been analyzed from the measurement results of shear stress, viscosity, current density and permeability. The electrical conductivity of silica-coated MWCNTs decreases with an increase of the shell thickness. However, the dynamic yield stress and viscoelastic properties under an external electric field increased when the shell thickness reached 20 nm and then decreased with the thickness up to 40 nm. However, the titania-coated MWCNT suspension with a shell thickness of 40 nm showed the highest dynamic yield stress compared to the other core-shell structured MWCNT suspension at the same volume fraction. It has been found that the material of the outermost shell plays an important role in the ER performance. It has been concluded that the electrical conductivity and the permittivity of the MWCNTs can be controlled by adjusting the coating thickness and sequence of inorganic materials.

Silica-graphene oxide hybrid composite particles and their electroresponsive characteristics

Silica-graphene oxide (Si-GO) hybrid composite particles were prepared by the hydrolysis of tetraethyl orthosilicate (TEOS) in the presence of hydrophilic GO obtained from a modified Hummers method. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images provided visible evidence of the silica nanoparticles grafted on the surface of GO, resulting in Si-GO hybrid composite particles. Energy dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD) spectra indicated the coexistence of silica and GO in the composite particles. The Si-GO hybrid composite particles showed better thermal stability than that of GO according to thermogravimetric analysis (TGA). The electrorheological (ER) characteristics of the Si-GO hybrid composite based ER fluid were examined further by optical microscopy and a rotational rheometer in controlled shear rate mode under various electric field strengths. Shear stress curves were fitted using both conventional Bingham model and a constitutive Cho-Choi-Jhon model. The polarizability and relaxation time of the ER fluid from dielectric spectra measured using an LCR meter showed a good correlation with its ER characteristics.

Conducting Material-incorporated Electrorheological Fluids: Core-shell Structured Spheres

Conducting material-based electro-responsive particles have become important as the smart soft matter in electrorheological (ER) fluids. These materials include conducting polymers, such as polyaniline, polypyrrole and poly(3,4-ethylenedioxythiophene), and carbon materials, such as carbon nanotubes and graphene oxide. Core-shell structured ER particles containing these materials as either core or shell species have attracted increasing interest owing to their outstanding advantages of an enhanced ER effect or diverse ER mechanism, lighter particulate density and lower cost. This paper summarizes the recent advances in synthesis methods as well as the critical characteristics of the core-shell structured particles, such as shear stress, yield stress and dielectric properties.

Electrorheology of nanofiber suspensions

Electrorheological (ER) fluid, which can be transformed rapidly from a fluid-like state to a solid-like state under an external electric field, is considered to be one of the most important smart fluids. However, conventional ER fluids based on microparticles are subjected to challenges in practical applications due to the lack of versatile performances. Recent researches of using nanoparticles as the dispersal phase have led to new interest in the development of non-conventional ER fluids with improved performances. In this review, we especially focus on the recent researches on electrorheology of various nanofiber-based suspensions, including inorganic, organic, and inorganic/organic composite nanofibers. Our goal is to highlight the advantages of using anisotropic nanostructured materials as dispersal phases to improve ER performances.