Methacrylated gelatin (GelMA) has been widely used as a tissue-engineered scaffold material, but only low-concentration GelMA hydrogels were found to be promising cell-laden bioinks with excellent cell viability. In this work, we reported a strategy for precise deposition of 5% (w/v) cell-laden GelMA bioinks into controlled microarchitectures with high cell viability using extrusion-based three-dimensional (3D) bioprinting. By adding gelatin into GelMA bioinks, a two-step cross-linking combining the rapid and reversible thermo-cross-linking of gelatin with irreversible photo-cross-linking of GelMA was achieved. The GelMA/gelatin bioinks showed significant advantages in processability because the tunable rheology and the rapid thermo-cross-linking of bioinks improved the shape fidelity after bioprinting. Here, the rheology, mechanical properties, and swelling of GelMA/gelatin bioinks with different concentration ratios were carefully characterized to obtain the optimized bioprinting setup. We successfully printed the 5% (w/v) GelMA with 8% (w/v) gelatin into 3D structures, which had the similar geometrical resolution as that of the structures printed by 30% (w/v) GelMA bioinks. Moreover, the cell viability of 5/8% (w/v) GelMA/gelatin bioinks was demonstrated by in vitro culture and cell printing of bone marrow stem cells (BMSCs). Larger BMSC spreading area was found on 5/8% (w/v) GelMA/gelatin scaffolds, and the BMSC viability after the printing of 5/8% (w/v) GelMA/gelatin cell-laden bioinks was more than 90%, which was very close to the viability of printing pure 5% (w/v) GelMA cell-laden bioinks. Therefore, this printing strategy of GelMA/gelatin bioinks may extensively extend the applications of GelMA hydrogels for tissue engineering, organ printing, or drug delivery.

We report on the preparation of dense monofilamentary MgB 2 /Ni and MgB 2 /Fe tapes with high critical current densities. In annealed MgB 2 /Ni tapes, we obtained transport critical current densities as high as 2.3 × 10 5 A/cm 2 at 4.2 K and 1.5 T, and for MgB 2 /Fe tapes 10 4 A/cm 2 at 4.2 K and 6.5 T. To the best of our knowledge, these are the highest transport j c values at 4.2 K reported for MgB 2 based tapes so far. An extrapolation to zero field of the MgB 2 /Fe data gives a critical current value of ~ 1 MA/cm 2 , corresponding to an critical current value well above 1000 A. The high j c values obtained after annealing are a consequence of sintering densification and grain reconnection. Fe does not react with MgB 2 and is thus an excellent sheath material candidate for tapes with self-field j c values at 4.2 K in excess of 1 MA/cm 2 .

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We report on the spontaneous segregation of double perovskite Ba 2 YTaO 6 (BYTO) nanoparticles within YBa 2 Cu 3 O 7 (YBCO) films forming a nanocomposite with two ternary oxides by the low cost and scalable chemical solution trifluoroacetate approach. Phase orientation, nanostructural and pinning studies are carried out by 2D x-ray diffraction, advanced scanning transmission electron microscopy and transport measurements, respectively. In this complex oxide nanocomposite system (YBCO-BYTO) the majority of the nanoparticles segregated within the (00l)-oriented superconducting matrix are randomly oriented. The presence of randomly oriented nanoparticles plays a key role in the generation of localized highly strained areas within the YBCO matrix which are suggested to strongly affect the superconducting properties. The incorporation of 6-10% of BYTO resulted in a maximum pinning force, at 77 K, three times higher than that obtained for a pristine sample, while T c was maintained at 89-90 K.