High Performance Flexible Actuator of Urchin-Like ZnO Nanostructure/Polyvinylenefluoride Hybrid Thin Film with Graphene Electrodes for Acoustic Generator and Analyzer.

A bass frequency response enhanced flexible polyvinylidene fluoride (PVDF) based thin film acoustic actuator is successfully fabricated. High concentrations of various zinc oxide (ZnO) is embedded in PVDF matrix, enhancing the ß phase content and the dielectric property of the composite thin film. ZnO acts as a nucleation agent for the crystallization of PVDF. A chemical vapor deposition grown graphene is used as electrodes, enabling high electron mobility for the distortion free acoustic signals. The frequency response of the fabricated acoustic actuator is studied as a function of the film thickness and filler content. The optimized film has a thickness of 80 µm with 30 wt% filler content and shows 72% and 42% frequency response enhancement in bass and midrange compared to the commercial PVDF, respectively. Also, the total harmonic distortion decreases to 82% and 74% in the bass and midrange regions, respectively. Furthermore, the composite film shows a promising potential for microphone applications. Most of all, it is demonstrated that acoustic actuator performance is strongly influenced by degree of PVDF crystalline.

A comparative study of the electrorheological properties of various N-doped nanomaterials using ammonia plasma treatment.

A new, simple method is reported to enhance the electrorheological (ER) activity of nanomaterials. Plasma treatment was the ideal technique owing to its ease of use, versatility, and common usage in mass production. Multi-gram quantities of ER nanomaterials with different morphologies, sizes, and compositions were successfully treated by ammonia plasma.

Enhanced Electroresponse of Alkaline Earth Metal-Doped Silica/Titania Spheres by Synergetic Effect of Dispersion Stability and Dielectric Property.

A series of alkaline earth metal-doped hollow SiO2/TiO2 spheres (EM-HST) are prepared as electrorheological (ER) materials via sonication-mediated etching method with various alkaline earth metal hydroxides as the etchant. The EM-HST spheres are assessed to determine how their hollow interior and metal-doping affects the ER activity. Both the dispersion stability and the dielectric properties of these materials are greatly enhanced by the proposed one-step etching method, which results in significant enhancement of ER activity. These improvements are attributed to increased particle mobility and interfacial polarization originating from the hollow nature of the EM-HST spheres and the effects of EM metal-doping. In particular, Ca-HST-based ER fluid exhibits ER performance which is 7.1-fold and 3.1-fold higher than those of nonhollow core/shell silica/titania (CS/ST) and undoped hollow silica/titania (HST)-based ER fluids, respectively. This study develops a versatile and simple approach to enhancing ER activity through synergetic effects arising from the combination of dispersion stability and the unique dielectric properties of hollow EM-HST spheres. In addition, the multigram scale production described in this experiment can be an excellent advantage for practical and commercial ER application.

Highly sensitive and multifunctional tactile sensor using free-standing ZnO/PVDF thin film with graphene electrodes for pressure and temperature monitoring.

We demonstrate an 80-µm-thick film (which is around 15% of the thickness of the human epidermis), which is a highly sensitive hybrid functional gauge sensor, and was fabricated from poly(vinylidene fluoride) (PVDF) and ZnO nanostructures with graphene electrodes. Using this film, we were able to simultaneously measure pressure and temperature in real time. The pressure was monitored from the change in the electrical resistance via the piezoresistance of the material, and the temperature was inferred based on the recovery time of the signal. Our thin film system enabled us to detect changes in pressure as small as 10 Pa which is pressure detection limit was 10(3)-fold lower than the minimum level required for artificial skin, and to detect temperatures in the range 20-120 °C.

Low-bandgap biophotonic nanoblend: a platform for systemic disease targeting and functional imaging.

Photonic nanomaterials have found wide applications in theranostics. We introduce here a design of all-organic photonic nanoparticles, different from traditional ones, in which we utilize nanoblend of a low-bandgap π-conjugated polymer (LB-CP) and polystyrene as the photonic core, surrounded by an FDA-approved polymeric surfactant. This design provides capability for efficient deep tissue imaging using highly penetrating near-infrared (NIR) excitation and emission of LB-CP and also allows us to incorporate a NIR phosphorescent oxygen-sensitive dye in the core to serve as a dual-emissive probe for hypoxia imaging. These biophotonic nanoblend (BNB) particles (∼20 nm in diameter) show facile blood circulation, efficient disease targeting and minimal liver filtration as well as sustained renal excretion in the intravenously administered mouse models, as noninvasively visualized by the NIR emission signals. In diseased mouse models, pathological tissue deoxygenation at hypoxic sites was successfully detected with ratiometric spectral information. We also show that our nanoformulation exhibits no apparent toxicity, thus serving as a versatile biophotonics platform for diagnostic imaging.

6"-Debromohamacanthin A, a bis (indole) alkaloid, inhibits angiogenesis by targeting the VEGFR2-mediated PI3K/AKT/mTOR signaling pathways.

Hamacanthins, bis (indole) alkaloids, are found in a few marine sponges, including Spongosorites sp. Hamacanthins have been shown to possess cytotoxic, antibacterial and antifungal activities. However, the precise mechanism for the biological activities of hamacanthins has not yet been elucidated. In the present study, the anti-angiogenic effects of 6"-debromohamacanthin A (DBHA), an active component of isolated hamacanthins, were evaluated in cultured human umbilical vascular endothelial cells (HUVEC) and endothelial-like cells differentiated from mouse embryonic stem (mES) cells. DBHA significantly inhibited vascular endothelial growth factor (VEGF)-induced cell proliferation, migration and tube formation in the HUVEC. DBHA also suppressed the capillary-like structure formation and the expression of platelet endothelial cell adhesion molecule (PECAM), an endothelial biomarker, in mES cell-derived endothelial-like cells. To further understand the precise molecular mechanism of action, VEGF-mediated signaling pathways were analyzed in HUVEC cells and mES cell-derived endothelial-like cells. DBHA suppressed the VEGF-induced expression of MAPKs (p38, ERK and SAPK/JNK) and the PI3K/AKT/mTOR signaling pathway. In addition, DBHA inhibited microvessel sprouting in mES/EB-derived embryoid bodies. In an ex vivo model, DBHA also suppressed the microvessel sprouting of mouse aortic rings. The findings suggest for the first time that DBHA inhibits angiogenesis by targeting the vascular endothelial growth factor receptor 2 (VEGFR2)-mediated PI3K/AKT/mTOR signaling pathway in endothelial cells.