Flexible piezoelectric sensor based on polyvinylidene fluoride/polyacrylonitrile/carboxy-terminated multi-walled carbon nanotube composite films for human motion monitoring.

Flexible piezoelectric devices have attracted much attention in the fields of intelligent devices and biomedicine because of their high sensitivity, stability, and flexibility. In this paper, a multifunctional flexible pressure sensor was prepared by adding polyacrylonitrile (PAN) and carboxylic-terminated multi-walled carbon nanotubes (c-MWCNTs) with polyvinylidene difluoride (PVDF) as the substrate. Theß-phase content of PVDF/PAN blended fibers compounded with c-MWCNT was up to 95%. At the same time, when PAN was added, the mechanical properties of the composite fibers were constantly improved. The results show that the polymer blending method can improve the comprehensive properties of PVDF composite. The flexible sensor prepared from the PVDF/PAN/c-MWCNT composite film has an output voltage of 2.1 V and a current of 7µA. The addition of c-MWCNT can largely improve the sensitivity of the sensor (4.19 V N-1). The sensor is attached to the finger and shows good output performance under different degrees of bending of the finger. The maximum output voltage of the sensor is 0.4 V, 0.56 V and 1.15 V when the finger bending angle is 30°, 60°, and 90°, respectively. Moreover, the developed piezoelectric sensor can monitor large-scale movements of various parts of the human body. Therefore, this composite material shows potential in areas such as motion monitoring and energy storage devices.

A Flexible Multifunctional PAN Piezoelectric Fiber with Hydrophobicity, Energy Storage, and Fluorescence.

Lightweight, flexible, and hydrophobic multifunctional piezoelectric sensors have increasingly important research value in contemporary society. They can generate electrical signals under the action of pressure and can be applied in various complex scenarios. In this study, we prepared a polyacrylonitrile (PAN) composite fiber doped with imidazolium type ionic liquids (ILs) and europium nitrate hexahydrate (Eu (NO3)3·6H2O) by a facile method. The results show that the PAN composite fibers had excellent mechanical properties (the elongation at break was 114% and the elastic modulus was 2.98 MPa), hydrophobic self-cleaning ability (water contact angle reached 127.99°), and can also emit light under UV light irradiation red fluorescence. In addition, thanks to the induction of the piezoelectric phase of PAN by the dual fillers, the composite fibers exhibited efficient energy storage capacity and excellent sensitivity. The energy density of PAN@Eu-6ILs reached a maximum of 44.02 mJ/cm3 and had an energy storage efficiency of 80%. More importantly, under low pressure detection, the sensitivity of the composite fiber was 0.69 kPa-1. The research results show that this PAN composite fiber has the potential to act as wearable piezoelectric devices, energy storage devices, and other electronic devices.

Eu3+-Doped Electrospun Polyvinylidene Fluoride-Hexafluoropropylene/Graphene Oxide Multilayer Composite Nanofiber for the Fabrication of Flexible Pressure Sensors.

The development of flexible materials with higher piezoelectric properties and electrostrictive response is of great significance in many applications such as wearable functional devices, flexible sensors, and actuators. In this study, we report an efficient fabrication strategy to construct a highly sensitive (0.72 kPa-1), red light-emitting flexible pressure sensor using electrospun Eu3+-doped polyvinylidene fluoride-hexafluoropropylene/graphene oxide composite nanofibers using a layer-by-layer technology. The high ß-phase concentration (96.3%) was achieved from the Eu3+-doped P(VDF-HFP)/GO nanofibers, leading to a high piezoelectricity of the composite nanofibers. We observed that a pressure sensor is enabled to generate an output voltage of 4.5 V. Furthermore, Eu3+-doped P(VDF-HFP)/GO composite nanofiber-based pressure sensors can also be used as an actuator as it has a good electrostrictive effect. At the same time, the nanofiber membrane has excellent ferroelectric properties and good fluorescence properties. These results indicate that this material has great application potential in the fields of photoluminescent fabrics, flexible sensors, soft actuators, and energy storage devices.

Social Support and Self-Efficacy as Mediating Factors Affecting the Association Between Depression and Medication Adherence in Older Patients with Coronary Heart Disease: A Multiple Mediator Model with a Cross-Sectional Study.

PURPOSE: Medication non-adherence is a major public health issue. Recent evidence suggests that depression, inadequate social support, and lower levels of self-efficacy are associated with poor medication adherence. However, the mechanism underlying the association among depression, social support, self-efficacy and medication adherence is unclear. This study aims to examine the mediating role of social support and self-efficacy between depression and medication adherence in older patients with coronary heart disease. PATIENTS AND METHODS: Data were collected from 238 hospitalized older patients with coronary heart disease. Depression, social support, self-efficacy, and medication adherence were assessed using structured questionnaires. A serial multiple mediation model was tested using the PROCESS macro for SPSS. RESULTS: A total of 238 older patients with CHD with a mean age of 70.5 years were involved in this cross-sectional study. Depression was negatively correlated with medication adherence in older patients with coronary heart disease. Social support and self-efficacy were positively associated with medication adherence, and fully mediated the relationship between depression and medication adherence. Three mediation paths were included in the model: (a) social support, (b) chain combination of social support and self-efficacy, and (c) self-efficacy. CONCLUSION: Social support and self-efficacy explain the association of depression and medication adherence in older CHD patients and may be the keys target for enhanced intervention to improve medication adherence in older CHD patients with depression.

Synthesis and characterization of 2-(2-benzhydrylnaphthyliminomethyl)pyridylnickel halides: formation of branched polyethylene.

A series of 2-(2-benzhydrylnaphthyliminomethyl)pyridine derivatives (L1-L3) was prepared and used to synthesize the corresponding bis-ligated nickel(II) halide complexes (Ni1-Ni6) in good yield. The molecular structures of representative complexes, namely the bromide Ni3 and the chloride complex Ni6, were confirmed by single crystal X-ray diffraction, and revealed a distorted octahedral geometry at nickel. Upon activation with either methylaluminoxane (MAO) or modified methylaluminoxane (MMAO), all nickel complex pre-catalysts exhibited high activities (up to 2.02 × 10(7) g(PE) mol(-1)(Ni) h(-1)) towards ethylene polymerization, producing branched polyethylene of low molecular weight and narrow polydispersity. The influence of the reaction parameters and the nature of the ligands on the catalytic behavior of the title nickel complexes were investigated.