Composites, Fabrication and Application of Polyvinylidene Fluoride for Flexible Electromechanical Devices: A Review

The technological development of piezoelectric materials is crucial for developing wearable and flexible electromechanical devices. There are many inorganic materials with piezoelectric effects, such as piezoelectric ceramics, aluminum nitride and zinc oxide. They all have very high piezoelectric coefficients and large piezoelectric response ranges. The characteristics of high hardness and low tenacity make inorganic piezoelectric materials unsuitable for flexible devices that require frequent bending. Polyvinylidene fluoride (PVDF) and its derivatives are the most popular materials used in flexible electromechanical devices in recent years and have high flexibility, high sensitivity, high ductility and a certain piezoelectric coefficient. Owing to increasing the piezoelectric coefficient of PVDF, researchers are committed to optimizing PVDF materials and enhancing their polarity by a series of means to further improve their mechanical–electrical conversion efficiency. This paper reviews the latest PVDF-related optimization-based materials, related processing and polarization methods and the applications of these materials in, e.g., wearable functional devices, chemical sensors, biosensors and flexible actuator devices for flexible micro-electromechanical devices. We also discuss the challenges of wearable devices based on flexible piezoelectric polymer, considering where further practical applications could be

Research of entrepreneurial problematics within the country-tourism and agro-tourism sectors

Wheat production is threatened by water shortages and groundwater over-draft in the North China Plain (NCP). In recent years, winter wheat has been increasingly sown extremely late in early to mid-November after harvesting cotton or pepper. To improve water use efficiency (WUE) and guide the extremely late sowing practices, a 3-year field experiment was conducted under two irrigation regimes (W1, one-irrigation, 75 mm at jointing; W2, two-irrigation, 75 mm at jointing and 75 mm at anthesis) in 3 cultivars differing in spike size (HS4399, small spike; JM22, medium spike; WM8, large spike). Wheat was sown in early to mid-November at a high seeding rate of 800-850 seeds m(-2). Average yields of 7.42 t ha(-1) and WUE of 1.84 kg m(-3) were achieved with an average seasonal evapotranspiration (ET) of 404 mm. Compared with W2, wheat under W1 did not have yield penalty in 2 of 3 years, and had 7.9% lower seasonal ET and 7.5% higher WUE. The higher WUE and stable yield under W1 was associated with higher 1000-grain weight (TGW) and harvest index (HI). Among the 3 cultivars, JM22 had 5.9%-8.9% higher yield and 4.2%-9.3% higher WUE than WM8 and HS4399. The higher yield in JM22 was attributed mainly to higher HI and TGW due to increased post-anthesis biomass and deeper seasonal soil water extraction. In conclusion, one-irrigation with a medium-sized spike cultivar JM22 could be a useful strategy to maintain yield and high WUE in extremely late-sown winter wheat at a high seeding rate in the NCP

Sequential Release of Paclitaxel and Imatinib from Core–Shell Microparticles Prepared by Coaxial Electrospray for Vaginal Therapy of Cervical Cancer

To optimize the anti-tumor efficacy of combination therapy with paclitaxel (PTX) and imatinib (IMN), we used coaxial electrospray to prepare sequential-release core–shell microparticles composed of a PTX-loaded sodium hyaluronate outer layer and an IMN-loaded PLGA core. The morphology, size distribution, drug loading, differential scanning calorimetry (DSC), Fourier transform infrared spectra (FTIR), in vitro release, PLGA degradation, cellular growth inhibition, in vivo vaginal retention, anti-tumor efficacy, and local irritation in a murine orthotopic cervicovaginal tumor model after vaginal administration were characterized. The results show that such core–shell microparticles were of spherical appearance, with an average size of 14.65 μm and a significant drug-loading ratio (2.36% for PTX, 19.5% for IMN, w/w), which might benefit cytotoxicity against cervical-cancer-related TC-1 cells. The DSC curves indicate changes in the phase state of PTX and IMN after encapsulation in microparticles. The FTIR spectra show that drug and excipients are compatible with each other. The release profiles show sequential characteristics in that PTX was almost completely released in 1 h and IMN was continuously released for 7 days. These core–shell microparticles showed synergistic inhibition in the growth of TC-1 cells. Such microparticles exhibited prolonged intravaginal residence, a >90% tumor inhibitory rate, and minimal mucosal irritation after intravaginal administration. All results suggest that such microparticles potentially provide a non-invasive local chemotherapeutic delivery system for the treatment of cervical cancer by the sequential release of PTX and IMN

Biomass at anthesis (BMA), post-anthesis (BMM) and remobilization amount (BMR) during grain filling in 3 years (2011, 2012, and 2013), under two irrigation regimes (W1 and W2), and in 3 cultivars (HS4399, JM22, WM8).

<p>Vertical bars represent standard deviations of the means.</p

Plant height (PH), spike length (SL) at maturity, primary and secondary root numbers for 3 cultivars across the 2011, 2012, and 2013 growing seasons.

<p>Plant height (PH), spike length (SL) at maturity, primary and secondary root numbers for 3 cultivars across the 2011, 2012, and 2013 growing seasons.</p

Soil water extraction (SWE) and total evapotranspiration (ET) in different growth periods during the 2011, 2012, and 2013 growing seasons, as affected by irrigation, cultivar, and year.

<p>Soil water extraction (SWE) and total evapotranspiration (ET) in different growth periods during the 2011, 2012, and 2013 growing seasons, as affected by irrigation, cultivar, and year.</p

Wheat biomass at maturity, harvest index (HI), grain yield, spikes m⁻², grains spike⁻¹, grains m⁻², 1000-grain weight (TGW), and water use efficiency for biomass (WUE_bm) and grain yield (WUE), as affected by irrigation, cultivar, and year.

<p>Wheat biomass at maturity, harvest index (HI), grain yield, spikes m⁻², grains spike⁻¹, grains m⁻², 1000-grain weight (TGW), and water use efficiency for biomass (WUE_bm) and grain yield (WUE), as affected by irrigation, cultivar, and year.</p

Monthly average air temperature, precipitation, and sunshine hours in the 2010–2011 (2011), 2011–2012 (2012) and 2012–2013 (2013) growing seasons.

<p>Monthly average air temperature, precipitation, and sunshine hours in the 2010–2011 (2011), 2011–2012 (2012) and 2012–2013 (2013) growing seasons.</p

Days and growing-degree days (GDD) during different growing periods for three cultivars in the 2011, 2012, and 2013 growing seasons.

<p>Days and growing-degree days (GDD) during different growing periods for three cultivars in the 2011, 2012, and 2013 growing seasons.</p