Miscibility, crystallization and annealing studies of poly(vinylidene fluoride)/hyperbranched polyester blends

Enhancing piezoelectric effect of PVDF electrospun fiber through NiO nanoparticles for wearable applications

Flexible electrospun fiber-based piezoelectric nanogenerator (PENG) has attracted a lot of interest due to its ability of generating electrical energy from mechanical energy sources. The present work aims to improve the piezoelectric output of PENG devices based on electrospun polyvinylidene fluoride (PVDF) doped with nickel oxide nanoparticles (NiO NPs) in different concentrations (2, 4, 6, 8 and 10 wt.-%). Crystalline phase changes and β-crystalline content in electrospun fibers were evaluated using XRD and FTIR-ATR, respectively. Surface morphology and surface roughness of the electrospun fibers were observed using FE-SEM and AFM, respectively. The hydrophobic nature of the fibers was analyzed using a wettability test. PENG output voltage and short-circuit current performance of neat PVDF and PVDF doped with NiO (PN) composite electrospun fibers were calculated using a customized variable-pressure setup with an optimized force of 1.0 kgf and 1.0 Hz frequency. Neat PVDF-based PENG exhibited only 1.7 V and 0.7 μA, whereas, PVDF doped with 6 wt.-% NiO NP (PN-6) based PENG generated a high output voltage of 5.5 V and 1.83 μA current. The optimized PN-6 PENG device is demonstrated for use in wearable devices towards identifying certain body movements like tapping, wrist movement, walking and running.

A Comprehensive Review on Processing, Development and Applications of Organofunctional Silanes and Silane-Based Hyperbranched Polymers

Since the last decade, hyperbranched polymers (HBPs) have gained wider theoretical interest and practical applications in sensor technology due to their ease of synthesis, highly branched structure but dimensions within nanoscale, a larger number of modified terminal groups and lowering of viscosity in polymer blends even at higher HBP concentrations. Many researchers have reported the synthesis of HBPs using different organic-based core-shell moieties. Interestingly, silanes, as organic-inorganic hybrid modifiers of HBP, are of great interest as they resulted in a tremendous improvement in HBP properties like increasing thermal, mechanical and electrical properties compared to that of organic-only moieties. This review focuses on the research progress in organofunctional silanes, silane-based HBPs and their applications since the last decade. The effect of silane type, its bi-functional nature, its influence on the final HBP structure and the resultant properties are covered in detail. Methods to enhance the HBP properties and challenges that need to be overcome in the near future are also discussed.

Fabrication of CuO-NP-Doped PVDF Composites Based Electrospun Triboelectric Nanogenerators for Wearable and Biomedical Applications

A flexible and portable triboelectric nanogenerator (TENG) based on electrospun polyvinylidene fluoride (PVDF) doped with copper oxide (CuO) nanoparticles (NPs, 2, 4, 6, 8, and 10 wt.-% w.r.t. PVDF content) was fabricated. The structural and crystalline properties of the as-prepared PVDF-CuO composite membranes were characterized using SEM, FTIR, and XRD. To fabricate the TENG device, the PVDF-CuO was considered a tribo-negative film and the polyurethane (PU) a counter-positive film. The output voltage of the TENG was analyzed using a custom-made dynamic pressure setup, under a constant load of 1.0 kgf and 1.0 Hz frequency. The neat PVDF/PU showed only 1.7 V, which further increased up to 7.5 V when increasing the CuO contents from 2 to 8 wt.-%. A decrease in output voltage to 3.9 V was observed for 10 wt.-% CuO. Based on the above results, further measurements were carried out using the optimal sample (8 wt.-% CuO). Its output voltage performance was evaluated as a function of varying load (1 to 3 kgf) and frequency (0.1 to 1.0 Hz) conditions. Finally, the optimized device was demonstrated in real-time wearable sensor applications, such as human motion and health-monitoring applications (respiration and heart rate).

Polyvinylidene Fluoride/Aromatic Hyperbranched Polyester of Third-Generation-Based Electrospun Nanofiber as a Self-Powered Triboelectric Nanogenerator for Wearable Energy Harvesting and Health Monitoring Applications

Flexible pressure sensors have played an increasingly important role in the Internet of Things and human-machine interaction systems. For a sensor device to be commercially viable, it is essential to fabricate a sensor with higher sensitivity and lower power consumption. Polyvinylidene fluoride (PVDF)-based triboelectric nanogenerators (TENGs) prepared by electrospinning are widely used in self-powered electronics owing to their exceptional voltage generation performance and flexible nature. In the present study, aromatic hyperbranched polyester of the third generation (Ar.HBP-3) was added into PVDF as a filler (0, 10, 20, 30 and 40 wt.% w.r.t. PVDF content) to prepare nanofibers by electrospinning. The triboelectric performances (open-circuit voltage and short-circuit current) of PVDF-Ar.HBP-3/polyurethane (PU)-based TENG shows better performance than a PVDF/PU pair. Among the various wt.% of Ar.HBP-3, a 10 wt.% sample shows maximum output performances of 107 V which is almost 10 times that of neat PVDF (12 V); whereas, the current slightly increases from 0.5 μA to 1.3 μA. The self-powered TENG is also effective in measuring human motion. Overall, we have reported a simpler technique for producing high-performance TENG using morphological alteration of PVDF, which has the potential for use as mechanical energy harvesters and as effective power sources for wearable and portable electronic devices.

Deformation-induced structure evolution of poly(butylene terephthalate)/poly(carbonate) blends during uniaxial stretching

Phase separation occurs during deformation for all the PBT/PC samples. At large strains, microfibril slippage plays a leading role in the macroscopic strain.