Piezoelectric PDMS/AlN Film for Osteogenesis in Vitro.

Bone defect and nonunion are complex diseases which are difficult to treat due to insufficient bone regeneration. Electrical stimulation has attracted attention as a promising strategy to induce and enhance bone regeneration. Self-powered and biocompatible materials have been widely explored and used in biomedical devices, owing to their ability to produce electrical stimulation without an external power source. We aimed to prepare a piezoelectric polydimethylsiloxane (PDMS)/aluminum nitride (AlN) film with excellent biocompatibility and osteoconductive ability for the growth of murine calvarial preosteoblast MC3T3-E1 cells. By applying vibration to stimulate body movement, the PDMS/AlN film demonstrated a current density of 2-6 µA cm-2, and the generated continuous alternating current (AC) effectively promoted MC3T3-E1 cell growth, viability, and osteoblastic related gene expression (genes runt-related transcription factor 2 [RUNX2], osteocalcin [OCN], alkaline phosphatase [ALP]) and exhibited higher mineralization. Compared to blank plates and nonvibrated PDMS/AlN films, the vibrated PDMS/AlN film showed rapid and superior osteogenic differentiation. The design of the biocompatible and flexible piezoelectric PDMS/AlN film overcame the poor processability, brittleness, and instability of electrical stimulation of traditional electroactive materials, demonstrating great potential in the application of electrical stimulation for bone tissue engineering.

Graphene/Carbon Paper Combined with Redox Active Electrolyte for Supercapacitors with High Performance.

Graphene/carbon paper is prepared by pyrolyzing graphene modified cellulose filter paper and directly used as a binder-free electrode to assemble a supercapacitor (SC) with a redox active electrolyte, containing a Fe3+/Fe2+ additive. By the graphene incorporation and the carbonization of the cellulose fibers, both the microstructure and the electrical conductivity of the carbon paper are promoted greatly. The filter paper derived carbon (FPC) electrode exhibits a specific capacitance (Cs) of 2832 F·g-1 in a 1 M H2SO4 + 0.5 M Fe3+/Fe2+ electrolyte at 1 A·g-1, which is about 81 times that in a normal H2SO4 electrolyte. With the modification of graphene, the capacitive performance of the SC is enhanced further and a remarkable Cs of 3396 F·g-1 at 1 A·g-1 is achieved for a graphene modified filter paper carbon (GFPC) electrode, which remains at ~632 F·g-1 at 10 A·g-1. The free standing GFPC electrode also exhibits good cycling stability (93.8% of capacitance retention after 2000 cycles) and an energy density of 118 Wh·kg-1 at a power density of 500.35 W·kg-1, all of which are much higher than those of FPC. These encouraging results suggest that the graphene modification of electrode materials combined with a Fe3+/Fe2+ redox active electrolyte is a prospective measure to fabricate SC with an ultrahigh performance.

Redox-Active Gel Electrolyte Combined with Branched Polyaniline Nanofibers Doped with Ferrous Ions for Ultra-High-Performance Flexible Supercapacitors.

In this work, the effects of utilizing an Fe2+/Fe3+ redox-active electrolyte and Fe2+-doped polyaniline (PANI) electrode material on the performance of an assembled supercapacitor (SC) were studied. The concentration of the redox couple additive in the electrolyte of the SC was optimized to be 0.5 M. With the optimized concentration of 0.4 M Fe2+, the doped PANI branched nanofibers electropolymerized onto titanium mesh were much thinner, cleaner, and more branched than normal PANI. A specific capacitance (Cs) of 8468 F g-1 for the 0.4 M Fe2+/PANI electrode in the 1 M H2SO4 + 0.5 M Fe2+/Fe3+ gel electrolyte and an energy density of 218.1 Wh kg-1 at a power density of 1854.4 W kg-1 for the resultant SC were achieved, which were much higher than those of the conventional PANI electrode tested in a normal H2SO4 electrolyte (404 F g-1 and 24.9 Wh kg-1). These results are among the highest reported for PANI-based SCs in the literature so far and demonstrate the potential effectiveness of this strategy to improve the electrochemical performance of flexible SCs by modifying both the electrode and electrolyte.