No abstract

With the rapid development of wearable devices, a highly sensitive flexible piezoelectric sensor shows tremendous potential for future demands.

The selection of scaffold materials and the optimization of scaffold morphological and mechanical properties are critical for successful bone tissue engineering. We fabricated porous scaffolds of nano-sized zirconia using a replication technique. The study aimed to explore the relationship between porosity, pore size, mechanical strength, cell adhesion, and cell proliferation in the zirconia scaffolds. Macro- and micro-structures and compressive strength were comparatively tested. Beagle bone marrow stromal cells were seeded onto the scaffolds to evaluate cell seeding efficiency and cell proliferation profile over 14 d of incubation. The zirconia scaffolds presented a complex porous structure with good interconnectivity of pores. By increasing the sinter cycles, the porosity and pore size of the scaffolds decreased, with mean values ranging from 92.7-68.0% and 830-577 μm, respectively, accompanied by increased compressive strengths of 0.6-4.4 MPa. Cell seeding efficiency and cell proliferation over the first 7 d of incubation increased when the porosity decreased, with cell viability highest in the scaffold with a porosity of 75.2%. After 7 d of incubation, the cell proliferation increased when the porosity increased, highest in the scaffolds with a porosity of 92.7%. These results showed that the zirconia scaffold with a porosity of 75.2% possesses favorable mechanical and biological properties for future applications in bone tissue engineering.

This paper reports our works on the preparation of the silver-nanoparticle-incorporated ultrafine polyimide (PI) ultrafine fibers via a direct ion exchange self-metallization technique using silver ammonia complex cation ([Ag(NH(3))(2)](+)) as the silver precursor and pyromellitic dianhydride (PMDA)/4,4'-oxidianiline (4,4'-ODA) polyimide as the matrix. The polyimide precursor, poly(amic acid) (PAA), was synthesized and then electrospun into ultrafine fibers. By thermally treating the silver(I)-doped PAA ultrafine fibers, where the silver(I) ions were loaded through the ion exchange reactions of the carboxylic acid groups of the PAA macromolecules with the [Ag(NH(3))(2)](+) cations in an aqueous solution, ultrafine polyimide fibers embedded with silver nanoparticles with diameters less than 20 nm were successfully fabricated. The fiber-electrospinning process, the ion exchange process, and various factors influencing the hybrid ultrafine fibers preparation process such as the thermal treatment atmospheres and the thermal catalytic oxidative degradation effect of the reduced silver nanoparticles were discussed. The ultrafine fibers were characterized by attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), inductively coupled plasma atomic emission spectroscopy (ICP-AES), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and thermogravimetric analysis (TGA).

No abstract

A novel polyimide nanofibrous membrane with porous-layer-coated morphology has been successfully fabricated by an in situ self-bonding and micro-crosslinking technique.

In order to achieve a high-performance flexible piezoelectric energy harvester (FPEH), a unique sandwich structure, that is, a PVDF film filled with FeTiNbO6 (FTN) semiconductor particles as an intermediate layer and a pure PVDF film as an upper and lower barrier layer, has been designed, and the corresponding PVDF-FTN/PVDFx-PVDF (P-FTNx-P) compact composite has been prepared by hot-pressing technology. The special sandwich structure combined with the introduction of FTN particles is beneficial to enhance the interfacial polarization and the content of the electroactive phase in PVDF. Together with the maximum piezoelectric voltage coefficient and the moderate Young’s modulus, the P-FTN15%-P FPEH exhibited the optimal energy-harvesting performance with a high power density of 110 μW/cm3 and a large charge density of 75 μC/m2 in cantilever mode. The outstanding design in this work is expected to provide a new way for the development of high-performance FPEH materials.

To build piezoceramics with high transduction coefficient (d 33 × g 33 ) is the key to improve the power generation capability of piezoelectric energy harvester. Here, a new targeted doping strategy has been proposed to significantly increase the energy density of piezoceramics. Taking the modification of 0.2Pb(Zn 1/3 Nb 2/ 3 )O 3 -0.8Pb(Zr 0.5 Ti 0.5 )O 3 (PZN-PZT) as an example, dual functions can be achieved by introducing appropriate amount of target-doped (Zn 0.1 Ni 0.9 )TiO 3 (ZTN9) based on its pyrolysis characteristics. On the one hand, Ni 2+ ions enter the perovskite matrix to replace Zn 2+ ions to form equivalent doping; on the other hand, it induces the formation of 0-3 ZnO/perovskite composite structure, and both of which promote the large increase in d 33 × g 33 due to the changes in the domain configuration are more conducive to the ferro-/piezoelectricity. In all compositions, 0.67 mol% ZTN9 added specimen has a maximum value (12 433 × 10 −15 m 2 /N) of the d 33 × g 33 . The cantilever piezoelectric energy harvester fabricated with this material generates up to 4.50 μW/mm 3 of power density at 1 g acceleration, which is capable of quickly charging a 47 μF electrolytic capacitor and then lit 135 parallel-connected commercial blue light-emitting diodes (LEDs), showing its important application in implementing self-powered microsensors.