2 research outputs found
Formation Performance, and Long-Term Stability of Nanostructured Ni-YSZ Thin Film Electrodes
No full textNickel
and yttria-stabilized zirconia (YSZ) composite anodes were
fabricated by a powder-free, polymeric precursor-based process, in
which Ni, Y, and Zr cations are redistributed by phase separation
at the nanoscale, forming YSZ and Ni(O). Transmission electron microscopy/energy-dispersive
X-ray spectroscopy analyses revealed for the first-time in the literature
that the nanocomposite thin film Ni-YSZ anodes had microstructures
consisting of alternating Ni and YSZ nanolayers. A pre-calcination
step applied in the oxidized state enhanced the interconnectivity
of the Ni and YSZ phases after reduction, which improved the electrochemical
performance. Electrochemical and microstructural analyses showed that
performance degradation upon long-term exposure to dilute hydrogen
at 600 °C was closely related to Ni coarsening in general. Evidently,
the pre-calcination step enhanced the performance stability of the
anodes by strengthening the YSZ network and thus inhibiting Ni agglomeration.
In addition, the deposition of a thin, electronically conductive CeO2 overlayer on top of the Ni-YSZ anode inhibited the excessive
agglomeration of Ni at the top surface. Our experiments showed that
the pre-calcination of Ni-YSZ anodes in the oxidized state with a
CeO2 overlayer gave the highest electrocatalytic performance, i.e., a polarization resistance of 0.72 Ω·cm2 at 600 °C, in dilute hydrogen, as well as the highest
long-term performance stability
Design of poly(vinyl pyrrolidone) and poly(ethylene glycol) microneedle arrays for delivering glycosaminoglycan, chondroitin sulfate, and hyaluronic acid
No full textOsteoarthritis (OA) is a prevalent joint disorder characterized by cartilage and bone degradation. Medical therapies like glucosaminoglycan (GAG), chondroitin sulfate (CS), and hyaluronic acid (HA) aim to preserve joint function and reduce inflammation but may cause side effects when administered orally or via injection. Microneedle arrays (MNAs) offer a localized drug delivery method that reduces side effects. Thus, this study aims to demonstrate the feasibility of delivering GAG, CS, and HA using microneedles in vitro. An optimal needle geometry is crucial for the successful application of MNA. To address this, here we employ a multi-objective optimization framework using the non-dominated sorting genetic algorithm II (NSGA-II) to determine the ideal MNA design, focusing on preventing needle failure. Then, a three-step fabrication approach is followed to fabricate the MNAs. First, the master (male) molds are fabricated from poly(methyl methacrylate) using mechanical micromachining based on optimized needle geometry. Second, a micro-molding with Polydimethylsiloxane (PDMS) is used for the fabrication of production (female) molds. In the last step, the MNAs were fabricated by microcasting the hydrogels using the production molds. Light microscopy (LIMI) confirms the accuracy of the MNAs manufactured, and in vitro skin insertion tests demonstrate failure-free needle insertion. Subsequently, we confirmed the biocompatibility of MNAs by evaluating their impact on the L929 fibroblast cell line, human chondrocytes, and osteoblasts
