Both oral and poster senior design presentations went well this year. Mercury Marine sponsored a project entitled Polymer Filament for Evaporative Pattern Prototyping that was advised by Prof. Drelich. Four MSE seniors including Alex Ball, Kristen Bull, Simon Eddy and Lewis Marshall worked on a selection of polymeric filament for 3D printing to rapidly prototype patterns for projects in the company lost foam aluminum casting; to replace expanded polystyrene foam.
Spontaneous spreading of a droplet on a solid surface is poorly understood from a macroscopic down to a molecular level. In our new publication entitled “Spontaneous Spreading of a Droplet: The Role of Solid Continuity and Advancing Contact Angle” and published in Langmuir, in collaboration with the Stevens Institute of Technology, we investigated the effect of surface topography and wettability on spontaneous spreading of a water droplet. Spreading force was measured for a suspended droplet that minimized interference of kinetic energy in the spontaneous spreading during its contact with solid surfaces of discontinuous (pillar) and continuous (pore) patterns with various shapes and dimensions. Results show that a droplet cannot spread spontaneously on pillared surfaces regardless of their shapes or dimensions due to the solid discontinuity. On the contrary, a droplet on pored surfaces can undergo spontaneous spreading whose force increases with a decrease in the advancing contact angle. Theoretical models based on both the system free energy and capillary force along the contact line validate the direct and universal dependency of the spontaneous spreading force on the advancing contact angle.
During the last few years, Zn alloys have been explored by the biomedical community as potential materials for bioabsorbable vascular stents due to their tolerable corrosion rates and tunable mechanical properties. In the new review coming from our research team and entitled “Zinc Alloys for Degradable Vascular Stent Applications” published in Acta Biomaterialia, the authors summarize recent progress made in developing Zn alloys for vascular stenting application. Novel Zn alloys are reviewed regarding their microstructural characteristics, mechanical properties, corrosion behavior and in vivo performance.
Roger Guillory (PhD Candidate) won the 2nd place in a poster competition under biomaterials category during the 147th TMS Annual Meeting in Phoenix, AZ. The title of his poster was “Long Term Biocompatibility of Zinc and its Alloys for Absorbable Vascular Scaffolds.”
Jeff Brookins (MS Candidate) won the 3rd place in the same competition with the poster entitled “Development and Characterization of Biodegradable Zinc Vascular Ligation Clips.”
Big congratulations to both of our talented students.
We organized and chaired the International Symposium on Biodegradable Materials in Medical Applications during the 147th TMS Annual Meeting in Phoenix, AZ. March 11-16, 2018. This two-day symposium comprised of four technical sessions and 27 presentations including 4 keynote addresses. Presentation given by Dr. Ehsan Mostaed entitled “Progress on Bioabsorbable Zn Alloys for Vascular Stent Applications” was a shining presentation of this meeting that attracted attention of experts in the field of biodegradable implants.
The program was strong and well attended, and we expect to repeat this symposium in 2020. We also had opportunity to meet our former students, Dr. Jan-Marten Seitz, who spent one year with us as a postdoctoral fellow, and collaborators.
We would like to share with you an announcement on one of the highest scientific achievements accomplished by two of our Editorial Advisory Board (EAB) members, Prof. Mietek Jaroniec from the Department of Chemistry and Biochemistry at Kent State University and Prof. Lei Jiang of the Chinese Academy of Sciences. Both of them have been recently listed on Clarivate Analytics’ 2017 list of Highly Cited Researchers in the world. They rank in the top 1 percent by citations for publications in the fields of both chemistry and materials science.
In our new collaborative study led by Prof. Eli Aghion from Ben-Gurion University of the Negev in Israel and described in the article entitled The Suitability of Zn– 1.3%Fe Alloy as a Biodegradable Implant Material, published in Metals, we evaluated 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.
In our new study described in article entitled “The most stable state of a droplet on anisotropic patterns: Support for a missing link,” surface tension and capillary forces were measured for water droplets in contact with anisotropic hydrophobic patterns made of microscopic ridges and grooves using a microbalance. Integrated with a CCD camera, the instrument allowed capturing of the synchronous images of a droplet during its spreading, compression, stretching and detachment. These images were used to analyze the evolution of a droplet shape and quantify its base diameter and contact angle in both longitudinal and traverse directions. The experiments confirmed that a water droplet spread preferentially along the longitudinal direction, on top of the ridges, following continuity of solid, and producing asymmetry in the drop shape. Switching the droplet wetting mode from advancing to receding causes the droplet to symmetrize its shape. It was found that the maximum adhesion between the droplet and hydrophobic pattern coincides with droplet base circularity and apparent contact angles of nearly identical values measured in longitudinal and traverse directions. These findings confirm that the most stable configuration for a liquid droplet on rough solid surface appears only when the droplet base is axisymmetric. It is also demonstrated that the Cassie-Baxter equation only pertains to the droplet in the most stable state, where the excess free energy is minimized.
Prof. Jeremy Goldman and Prof. Jaroslaw Drelich are the principal investigators on a new one-year project entitled “Exploratory Research to Suppress Intimal Hyperplasia by Controlling Zinc Implant Biodegradation” awarded with $217,791 by the US National Institute of Health (NIH).