The suitability of Zn–1.3% Fe alloy as a biodegradable implant material

Efforts to develop metallic zinc for biodegradable implants have significantly advanced following an earlier focus on magnesium (Mg) and iron (Fe). Mg and Fe base alloys experience an accelerated corrosion rate and harmful corrosion products, respectively. The corrosion rate of pure Zn, however, may need to be modified from its reported ~20 µm/year penetration rate, depending upon the intended application. The present study aimed at evaluating the possibility of using Fe as a relatively cathodic biocompatible alloying element in zinc that can tune the implant degradation rate via microgalvanic effects. The selected Zn–1.3wt %Fe alloy composition produced by gravity casting was examined in vitro and in vivo. The in vitro examination included immersion tests, potentiodynamic polarization and impedance spectroscopy, all in a simulated physiological environment (phosphate-buffered saline, PBS) at 37 °C. For the in vivo study, two cylindrical disks (seven millimeters diameter and two millimeters height) were implanted into the back midline of male Wister rats. The rats were examined post implantation in terms of weight gain and hematological characteristics, including red blood cell (RBC), hemoglobin (HGB) and white blood cell (WBC) levels. Following retrieval, specimens were examined for corrosion rate measurements and histological analysis of subcutaneous tissue in the implant vicinity. In vivo analysis demonstrated that the Zn–1.3%Fe implant avoided harmful systemic effects. The in vivo and in vitro results indicate that the Zn–1.3%Fe alloy corrosion rate is significantly increased compared to pure zinc. The relatively increased degradation of Zn–1.3%Fe was mainly related to microgalvanic effects produced by a secondary Zn11Fe phase

Mechanical properties of boehmeria nivea natural fabric reinforced epoxy matrix composite prepared by vacuum-assisted resin infusion molding

Natural lignocellulosic fibers and corresponding fabrics have been gaining notoriety in recent decades as reinforcement options for polymer matrices associated with industrially applied composites. These natural fibers and fabrics exhibit competitive properties when compared with some synthetics such as glass fiber. In particular, the use of fabrics made from natural fibers might be considered a more ecient alternative, since they provide multidirectional reinforcement and allow the introduction of a larger volume fraction of fibers in the composite. In this context, it is important to understand the mechanical performance of natural fabric composites as a basic condition to ensure ecient engineering applications. Therefore, it is also important to recognize that ramie fiber exhibiting superior strength can be woven into fabric, but is the least investigated as reinforcement in strong, tough polymers to obtain tougher polymeric composites. Accordingly, this paper presents the preparation of epoxy composite containing 30 vol. % Boehmeria nivea fabric by vacuum-assisted resin infusion molding technique and mechanical behavior characterization of the prepared composite. Obtained results are explained based on the fractography studies of tested samples

Guidelines to measurements of reproducible contact angles using a sessile-drop technique

The current broad interest in wetting characterization of solid surfaces is driven by recent advances in the formulation of surfaces and coatings that are superhydrophobic, superhydrophilic, oleophobic, oleophilic and so on. Unfortunately, the contact angle data presented in many publications raise some concerns among the surface chemists and physicists who work with contact angle measurement techniques on a regular basis. In those articles, best practices are often ignored, and the data presented are limited to the static contact angles measured for small droplets, a few times smaller than typically recommended. The reported contact angles are neither advancing nor receding, and their reproducibility in different laboratories is therefore questionable. In this note, guidelines to measurements of reproducible and reliable advancing and receding contact angles are summarized

Characterization of Biodegradable Medical Materials.

Since the twentieth century, the development of artificial implants needed in surgical restorative health care has been dominated by biologically inert and corrosion-resistant materials. These permanent implants either need to be removed through a secondary surgery or remain in the host body for a lifetime. Remaining implants often cause long-term complications either from slow but progressive corrosion and material properties deterioration or as a result of characteristics that are different from the intruded biological environment. The paradigm of permanent implants has been challenged over the last two decades through the development of biodegradable implant materials. Biodegradable implants can provide the biomechanical support necessary throughout the healing process but will eventually dissolve and be replaced by the host tissue. Biodegradable polymers were the primary candidates for implants, given the ease of processing and shaping, together with their predictable degradation products. However, their low mechanical properties, poor visibility in the body, and acidification of the implantation site during degradation have limited widespread clinical application of polymer implants. Biodegradable metallic materials have superior mechanical properties and have been investigated as candidate materials for vascular, orthopedic, suturing, and other medical applications since the beginning of the twenty-first century. However, new materials for medical applications must fulfill clinical requirements related to deployment, efficacy, and device safety, which pose challenges to metallurgists in designing, characterizing, and testing these materials, as discussed in the following collection of papers written by experts in the field of biodegradable implants

Fish Skin: A Natural Inspiration for Innovation

Natural materials and the structures they form, developed and perfected through millions of years of evolution, have long inspired researchers for innovations in science and engineering. One example, fish scales are notable for their strength, toughness, flexibility, and lightweight. These properties are the result of collagen fibrils and hydroxyapatite crystals that have been arranged into three-layer structures through mechanical locking and chemical bonds, via a process that is still poorly understood. This review aims to compile the established knowledge on the composition, structure, and surface/interfacial features of fish scales. Using mainly Arapaima gigas as a focus, published information and supplementary data acquired through imaging, analytical techniques, and tensiometry are combined. This is done to take a closer look at the surfaces and interfaces of fish scales to identify their unique features and begin to overcome some of the limited understanding of surface functionalities that are created by nature

Deformation of soft colloidal probes during AFM pull-off force measurements: Elimination of nano-roughness effects

The forces needed to remove polystyrene (PS) and polyethylene (PE) particles from silicon wafers were measured using the atomic force microscopy colloidal probe technique. The polymeric probes had surfaces with nano-sized asperities. The ability to deform these asperities and conform to the topography of the substrate surface allowed the soft probes to mitigate roughness effects on the measured pull-off forces. Adequate deformations for surface asperities on PS and PE probes that resulted in reproducible probe-substrate contact area required loads of approx. 0.8-4 μN. For these applied loads the standard deviation in measured pull-off forces was reduced to 0.5-2.7%. © VSP 2005

Superhydrophilic and superwetting surfaces: Definitions and mechanisms of control

The term superhydrophobicity was introduced in 1996 to describe water-repellent fractal surfaces, made of a hydrophobic material, on which water drops remain as almost perfect spheres and roll off such surfaces leaving no residue. Today, superhydrophobic surfaces are defined as textured materials (and coatings) on (nonsmooth) surfaces on which water forms contact angles 150° and larger, with only a few degrees of contact angle hysteresis (or sliding angle). The terms superhydrophilicity and superwetting were introduced a few years after the term superhydrophobicity to describe the complete spreading of water or liquid on substrates. The definition of superhydrophilic and superwetting substrates has not been clarified yet, and unrestricted use of these terms sometimes stirs controversy. This Letter briefly reviews the superwetting phenomenon and offers a suggestion on defining superhydrophilic and superwetting substrates and surfaces

Meaningful contact angles in flotation systems: Critical analysis and recommendations

Froth flotation was invented in the nineteenth century. Since then, many laboratories have been committed to both fundamental and applied research on the collection of particles by dispersed gas bubbles in aqueous solutions of electrolytes, in particular those working on the processing of natural resources. However, despite the tremendous progress made in the characterization of particles and their surfaces and understanding particle–bubble interactions, supported by detailed recordings of gas bubble attachments to both bulk specimens and particles, the flotation process remains poorly correlated with the wetting characteristics of particle surfaces. In fact, the contact angles used frequently to describe the wettability of mineral surfaces remain among the most controversial, misunderstood and misinterpreted values in mineral processing literature. Contrary to wide-ranging beliefs, it is the authors’ position that neither the methodology of contact angle measurements nor the selection of contact angles important to the particle flotation process is properly executed when analyzing the flotation process. In this paper, the authors provide a brief personal perspective on some of the misconceptions on contact angles and the importance of additional fundamental studies in the area of mineral particle flotation

Physics and applications of superhydrophobic and superhydrophilic surfaces and coatings

The terms superhydrophobicity and superhydrophilicity were introduced not very long ago, in 1996 and 2000, respectively. The former is used to describe exceptionally weak and the latter used to indicate strong interactions of materials and coatings with bulk water, controlled entirely by surface topography and material chemistry. An explosion of research on fabrication of superhydrophobic and superhydrophilic surfaces and coatings was noticed almost immediately after the concepts appeared in the technical literature, with hundreds of reports now published annually. The interest in this new class of surfaces/coatings is driven by an emerging market for water-repellant, snow- and ice-phobic products and formulations, water antifogging screens, windows and lenses, antifouling coatings, microfluidic devices, coatings for enhanced boiling heat transfer, foils for food packaging and many other products. The popularity of this emerging subdiscipline of surface chemistry can also be attributed to uncomplicated fabrication technologies that can produce superhydrophobic or superhydrophilic surfaces and coatings, in addition to the simplicity of the testing techniques used, such as contact angle measurements. In this article, the physics behind superhydrophobic and superhydrophilic effects are reviewed and several examples of applications of superhydrophobic and superhydrophilic surfaces and coatings are provided