Synthesized biocompatible and conductive ink for 3D printing of flexible electronics.

Three-dimensional (3D) printing is an efficient technique for the fabrication of electronic devices. It also enables the use conductive of biomaterials in various applications, such as implants and flexible devices. Designing a new bioink is extremely challenging. For bioelectronics devices, bioink materials should be printable, flexible, conductive, harmless to cells, and sufficiently strong to maintain their shape when immersed in nutrients or under pressure. Over the past few years, several flexible conductive bioinks have been developed that are based on composite pastes containing a biopolymer and conductive micro- and nanoscale materials in the form of metallic particles, conducting polymers, or a mixture of them. Herein, we report a new strategy for the fabrication of a bioink for a commercial 3D printer with the desired conductivity, mechanical properties, and biocompatibility, using a poly(glycerol-co-sebacate) (PGS)-based polymer and zinc. The PGS-based polymer and lithium phenyl-2,4,6-trimethylbenzoylphosphinate (as a photoinitiator) were added to the zinc, and then, the prepared bioink was polymerized during 3D printing under visible light. According to a microstructural investigation using scanning electron microscopy, the zinc particles were homogeneously distributed in the PGSA matrix. The conductivity of bioink increases with chemical sintering and with an increase in the amount of zinc particles. Based on rheology tests, the appropriate printable composition is 60% zinc and 40% PGS-based polymer. This bioink exhibited remarkable mechanical and adhesive properties in comparison with the PGS-based polymer without zinc, according to tensile, compression, lap shear, wound closure, and burst pressure modules. In vitro and in vivo results indicated that the bioink was not toxic to the cells or the animal over a period of culturing.

Bio-corrosion behavior and mechanical characteristics of magnesium-titania-hydroxyapatite nanocomposites coated by magnesium-oxide flakes and silicon for use as resorbable bone fixation material.

This study was aimed to improve of the corrosion resistance and mechanical properties of Mg/15TiO2/5HA nanocomposite by silicon and magnesium oxide coatings prepared using a powder metallurgy method. The phase evolution, chemical composition, microstructure and mechanical properties of uncoated and coated samples were characterized. Electrochemical and immersion tests used to investigate the in vitro corrosion behavior of the fabricated samples. The adhesion strength of ~36MPa for MgO and ~32MPa for Si/MgO coatings to substrate was measured by adhesion test. Fabrication a homogenous double layer coating with uniform thicknesses consisting micro-sized particles of Si as outer layer and flake-like particles of MgO as the inner layer on the surface of Mg/15TiO2/5HA nanocomposite caused the corrosion resistance and ductility increased whereas the ultimate compressive stress decreased. However, after immersion in SBF solution, Si/MgO-coated sample indicates the best mechanical properties compared to those of the uncoated and MgO-coated samples. The increase of cell viability percentage of the normal human osteoblast (NHOst) cells indicates the improvement in biocompatibility of Mg/15TiO2/5HA nanocomposite by Si/MgO coating.