Colloidal and electrophoretic behavior of polymer particulates in suspension

Electrophoretic deposition of polymers and proteins for biomedical applications

This review is focused on new electrophoretic deposition (EPD) mechanisms for deposition biomacromolecules, such as biopolymers, proteins and enzymes. Among the rich literature sources of EPD of biopolymers, proteins and enzymes for biomedical applications we selected papers describing new fundamental deposition mechanisms. Such deposition mechanisms are of critical importance for further development of EPD method and its emerging biomedical applications. Our goal is to emphasize innovative ideas which have enriched colloid and interface science of EPD during recent years. We describe various mechanisms of cathodic and anodic EPD of charged biopolymers. Special attention is focused on in-situ chemical modification of biopolymers and crosslinking techniques. Recent innovations in the development of natural and biocompatible charged surfactants and film forming agents are outlined. Among the important advances in this area are the applications of bile acids and salts for EPD of neutral polymers. Such innovations allowed for the successful EPD of various electrically neutral functional polymers for biomedical applications. Particularly important are biosurfactant-polymer interactions, which facilitate dissolution, dispersion, charging, electrophoretic transport and deposit formation. Recent advances in EPD mechanisms addressed the problem of EPD of proteins and enzymes related to their charge reversal at the electrode surface. Conceptually new methods are described, which are based on the use of biopolymer complexes with metal ions, proteins, enzymes and other biomolecules. This review describes new developments in co-deposition of biomacromolecules and future trends in the development of new EPD mechanisms and strategies for biomedical applications.

Electrophoretic Co-deposition of Polyetheretherketone and Graphite Particles: Microstructure, Electrochemical Corrosion Resistance, and Coating Adhesion to a Titanium Alloy

The present study explores the possibilities of fabricating a graphite/polyetheretherketone (PEEK) composite coating on a Ti-6Al-4V titanium alloy through duplex treatment consisting of electrophoretic deposition (EPD) and heat treatment. It has been found that the electrophoretic co-deposition of graphite and PEEK microparticles can be performed from environmentally-friendly pure ethanolic suspensions. Zeta potential measurements and a study of the interaction between both particle types with the use of transmission electron microscopy allowed potential mechanisms of particle co-deposition to be indicated. Microstructure characterization was performed on macro-, micro- and nanoscale using visible light microscopy, X-ray diffractometry and electron microscopy. This allowed the coating homogeneity and distribution of graphite particles in the polymer matrix to be described. Graphite particles in the form of graphene nanosheet packages were relatively evenly distributed in the coating matrix and oriented parallel to the coating surface. The heat-treated coatings showed high scratch resistance and no adhesive type destruction was observed, but they were highly susceptible to deformation. The corrosion measurements were performed with use of electrochemical techniques like open circuit potential and linear sweep voltamperometry. The coated alloy indicated better electrochemical corrosion resistance compared with the uncoated alloy. This work showed the high versatility of the electrophoretic co-deposition of graphite and PEEK particles, which combined with post-EPD heat treatment allows composite coatings to be fabricated with controlled distribution of graphite particles.

Influence of polyetheretherketone coatings on the Ti-13Nb-13Zr titanium alloy's bio-tribological properties and corrosion resistance

Polyetheretherketone (PEEK) coatings of 70-90μm thick were electrophoretically deposited from a suspension of PEEK powder in ethanol on near-β Ti-13Nb-13Zr titanium alloy. In order to produce good quality coatings, the composition of the suspension (pH) and optimized deposition parameters (applied voltage and time) were experimentally selected. The as-deposited coatings exhibited the uniform distribution of PEEK powders on the substrate. The subsequent annealing at a temperature above the PEEK melting point enabled homogeneous, semi-crystalline coatings with spherulitic morphology to be produced. A micro-scratch test showed that the coatings exhibited very good adhesion to the titanium alloy substrate. Coating delamination was not observed even up to a maximal load of 30N. The PEEK coatings significantly improved the tribological properties of the Ti-13Nb-13Zr alloy. The coefficient of friction was reduced from 0.55 for an uncoated alloy to 0.40 and 0.12 for a coated alloy in a dry sliding and sliding in Ringer's solution, respectively. The PEEK coatings exhibited excellent wear resistance in both contact conditions. Their wear rate was more than 200 times smaller compared with the wear rate of the uncoated Ti-13Nb-13Zr alloy. The obtained results indicate that electrophoretically deposited PEEK coatings on the near-β titanium alloy exhibit very useful properties for their prospective tribological applications in medicine.

Electric field-controlled semiconductor nanorod assembly in solution: mechanistic insights from non-equilibrium molecular dynamics

Non-equilibrium molecular dynamics (MD) of small, charged cadmium selenide nanorods have been carried out in the absence and presence of static applied electric fields. In the absence of applied fields, it was found that opposite dipolar alignment (antiferromagnetic) was achieved, along with self-assembly of the nanorods. However, in the case of induced electrophoresis in applied fields, the rods approached each other less readily, while at and above a field intensity of 0.05 V/Å, preferential alignment with the field was achieved for all rods, in contrast to the zero-field case. These results have implications for electric field-mediated control of nanorod assembly in solution, of key importance in a wide range of areas from photovoltaics to energy storage.

Electrophoretic Deposition of PEEK-TiO2 Composite Coatings on Stainless Steel

Electrophoretic deposition (EPD) has been successfully used to deposit composite coatings composed of polyetheretherketone (PEEK) and titanium dioxide (TiO2) nanoparticles on 316L stainless steel substrates. The suspensions of TiO2 nanoparticles and PEEK microparticles for EPD were prepared in ethanol. PEEK-TiO2 composite coatings were optimized using suspensions containing 6wt% PEEK-TiO2 in ethanol with a 3:1 ratio of PEEK to TiO2 in weight and by applying a potential difference of 30 V for 1 minute. A heat-treatment process of the optimized PEEK-TiO2 composite coatings was performed at 335°C for 30 minutes with a heating rate of 10°Cminto densify the deposits. The EPD coatings were microstructurally evaluated by scanning electron microscopy (SEM). It was demonstrated that EPD is a convenient and rapid method to fabricate PEEK/TiO2 coatings on stainless steel which are interesting for biomedical applications.

Electrophoretic deposition of poly(3-decylthiophene) onto gold-mounted cadmium selenide nanorods

Molecular mechanisms of electrophoretic deposition (EPD) of poly(3-decylthiophene) (P3DT) molecules onto vertically aligned cadmium selenide arrays have been studied using large-scale, nonequilibrium molecular dynamics (MD), in the absence and presence of static external electric fields. The field application and larger polymer charges accelerated EPD. Placement of multiple polymers at the same lateral displacement from the surface reduced average deposition times due to "crowding", giving monolayer coverage. These findings were used to develop and validate Brownian dynamics simulations of multilayer polymer EPD in scaled-up systems with larger inter-rod spacings, presenting a generalized picture in qualitative agreement with random sequential adsorption.