Since the invention of froth flotation in 19th century, many laboratories are committed to both fundamental and applied research on collection of particles by dispersed gas bubbles in aqueous solutions of electrolytes, especially those working on processing of natural resources. However, in spite of tremendous progress made in characterization of particles and their surfaces and understanding the particle-bubble interactions, supported with 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 wettability of mineral surfaces remain among the most controversial, misunderstood and misinterpreted values in mineral processing literature. Contrary to wide-ranging beliefs, in the new contribution by Prof. Drelich (Michigan Tech) and Prof. Marmur (Technion, Israel) argue that neither the methodology of contact angle measurements nor selection of contact angles important to the particle flotation process are properly executed when analyzing flotation process. In their new paper published in Surface Innovations and entitled Meaningful contact angles in flotation systems: critical analysis and recommendations, the authors provide a brief personal prospective on some of the misconceptions on contact angles and the importance of additional fundamental studies in the area of mineral particles flotation.
The research team from the Ben-Gurion University of the Negev and led by Prof. Eli Aghion published, in collaboration with Prof. Goldman and SURFI, a new paper on two new zinc base alloys, Zn-1%Mg and Zn-1%Mg-0.5%Ca, which could serve as structural materials for biodegradable implants. This examination was carried out in in vitro conditions including immersion test, potentiodynamic polarization analysis, electrochemical impedance spectroscopy and stress corrosion cracking assessment in terms of slow strain rate testing. In order to assess the cytotoxicity of the tested alloys, indirect cell viability was preformed using Saos-2 cells. The results obtained demonstrate that both zinc alloys can be considered as adequate candidates for biodegradable implants with a relative advantage to the Zn-1%Mg alloy in terms of its corrosion resistance and SCC performance.
The paper was published in the Journal of Materials Science: Materials in Medicine and is entitled In vitro behavior of biodegradable implants based on Zn-1%Mg and Zn-1%Mg-0.5%Ca alloys.
Surface Innovations Team welcomes a new member, Dr. Ehsan Mostaed. Dr. Mostaed has strong expertise in metallurgy, and his recent research concentrated on formulation and testing of bioabsorbable Zn-based materials. He joins as from Politecnico Di Milano in Italy. In Italy, working with Prof. Maurizio Vedani, Dr. Mostaed formulated and characterized a series of new Zn-based alloys. He will continue exploration of Zn-based alloys at Michigan Tech.
The SURFI Team welcomes a new PhD candidate to our team, Mr. Morteza Shaker. Morteza comes from Iran with a strong background in metallurgy and will work on Zn-based alloys for medical applications under a supervision of both Dr. Drelich and Dr. Kampe.
Dr. Jeremy Schaffer from Fort Wayne Metals represented our program on Zn-based biodegradable stents and delivered a keynote address during the 9th Biometals: Symposium on Biodegradable Metals for Biomedical Applications in Bertinoro, Italy (August 27 – September 1). His presentation was entitled Multi-parameter Instability of Zn-Mg Alloy Wires, and was co-authored by A.J. Griebel, C. Galligan, P.K. Bowen, J. Goldman, and J.W. Drelich.
Prof. Jaroslaw Drelich is the principal investigator on a project entitled “MRI:Acquisition of an Atomic Force Microscope for Force Measurement, Single-Molecule Manipulation and other Applications” that has received a $135,669 research and development grant from the National Science Foundation (NSF).
We are glad to share with you the content of the 3rd issue of 2017 of Surface Innovations with eight papers on surface phenomena and nanosized systems, which were selected and assembled by Prof. Ludmila Boinovich from the Russian Academy of Sciences
Our new paper on antimicrobial material was published in the Materials journal and is entitled Novel Durable Antimicrobial Ceramic with Embedded Copper Sub-Microparticles for a Steady-State Release of Copper Ions. Using pottery clay, porous ceramic stones were molded and then decorated with copper sub-microparticles inside the pores. Copper added antimicrobial functionality to the clay-based ceramic and showed ability in disinfecting water. Populations of both Staphylococcus aureus and Klebsiella pneumoniae in contaminated water were reduced by >99.9% in 3 hours when exposed to an antimicrobial stone. This antimicrobial performance is attributed to a slow release of copper into water at both room and elevated temperatures. Copper was leached by water to produce ion concentrations in water at a level of 0.05-0.20 ppm after 24 to 72-hour immersion tests. This concentration was reproducible over a number of cycles >400. To our knowledge, this is the first formulation of copper sub-microparticles inside the porous structure of commercial-sized ceramic stones that can disinfect bacteria-contaminated water over a period of at least several months.
Zinc (Zn) has recently been introduced as a promising new metal candidate for biodegradable vascular stent applications with a favorable degradation rate and biocompatibility. Corrosion resistant metal stents are often coated with drug-eluting polymer layers to inhibit harmful biological responses. In our new paper entitled “Effect of PLLA Coating on Corrosion and Biocompatibility of Zinc in Vascular Environment” and published in Surface Innovations, we investigated the interaction between biodegradable zinc metal with a conventional biodegradable polymer coating. Zn wire with a diameter of 0.25 mm was surface modified using 3-(trimethoxysilyl) propyl methacrylate (MPS) and then coated with a 1-12 µm film of poly (L-lactic-acid) (PLLA). The corrosion behavior of PLLA/MPS-coated Zn wires was studied in simulated body fluid using electrochemical impedance spectroscopy. An increase in the impedance from <1,000 to >15,000 ohms cm2 was recorded for Zn wire after its coating with PLLA. The PLLA/MPS-coated Zn specimens were implanted into the abdominal rat aorta to assess their biodegradation and biocompatibility as compared to uncoated Zn wires. PLLA/MPS-coated wires corroded at approximately half the rate as unmodified Zn during the first 4.5 months. A histological analysis of the biological tissue surrounding the Zn implants revealed a reduction in biocompatibility of the polymer-coated samples, as indicated by increasing cell toxicity and neointimal hyperplasia.