Interfacial Engineering of PVDF-TrFE toward Higher Piezoelectric, Ferroelectric, and Dielectric Performance for Sensing and Energy Harvesting Applications.

The electrical properties of pristine fluoropolymers are inferior due to their low polar crystalline phase content and rigid dipoles that tend to retain their fixed moment and orientation. Several strategies, such as electrospinning, electrohydrodynamic pulling, and template-assisted growing, have been proven to enhance the electrical properties of fluoropolymers; however, these techniques are mostly very hard to scale-up and expensive. Here, a facile interfacial engineering approach based on amine-functionalized graphene oxide (AGO) is proposed to manipulate the intermolecular interactions in poly(vinylidenefluoride-trifluoroethylene) (PVDF-TrFE) to induce ß-phase formation, enlarge the lamellae dimensions, and align the micro-dipoles. The coexistence of primary amine and hydroxyl groups on AGO nanosheets offers strong hydrogen bonding with fluorine atoms, which facilitates domain alignment, resulting in an exceptional remnant polarization of 11.3 µC cm-2 . PVDF-TrFE films with 0.1 wt.% AGO demonstrate voltage coefficient, energy density, and energy-harvesting figure of merit values of 0.30 Vm N-1 , 4.75 J cm-3 , and 14 pm3  J-1 , respectively, making it outstanding compared with state-of-the-art ceramic-free ferroelectric films. It is believed that this work can open-up new insights toward structural and morphological tailoring of fluoropolymers to enhance their electrical and electromechanical performance and pave the way for their industrial deployment in next-generation wearables and human-machine interfaces.

Inkjet Printing of Electrodes on Electrospun Micro- and Nanofiber Hydrophobic Membranes for Flexible and Smart Textile Applications.

With the increasing demand for smart textile and sensor applications, the interest in printed electronics is rising. In this study, we explore the applicability of electrospun membranes, characterized by high porosity and hydrophobicity, as potential substrates for printed electronics. The two most common inks, silver and carbon, were used in inkjet printing to create a conductive paths on electrospun membranes. As substrates, we selected hydrophobic polymers, such as polyimide (PI), low- and high-molecular-weight poly (vinyl butyral-co-vinyl alcohol-co-vinyl acetate) (PVB) and polystyrene (PS). Electrospinning of PI and PVB resulted in nanofibers in the range of 300-500 nm and PVB and PS microfibers (1-5 µm). The printed patterns were investigated with a scanning electron microscope (SEM) and resistance measurements. To verify the biocompatibility of printed electrodes on the membranes, an indirect cytotoxicity test with cells (MG-63) was performed. In this research, we demonstrated good printability of silver and carbon inks on flexible PI, PVB and PS electrospun membranes, leading to electrodes with excellent conductivity. The cytotoxicity study indicated the possibility of using manufactured printed electronics for various sensors and also as topical wearable devices.

Droplet-Based Techniques for Printing of Functional Inks for Flexible Physical Sensors.

Printed electronics (PE) is an emerging technology that uses functional inks to print electrical components and circuits on variety of substrates. This technology has opened up new possibilities to fabricate flexible, bendable, and form-fitting devices at low-cost and fast speed. There are different printing technologies in use, among which droplet-based techniques are of great interest as they provide the possibility of printing computer-controlled design patterns with high resolution, and greater production flexibility. Nanomaterial inks form the heart of this technology, enabling different functionalities. To this end, intensive research has been carried out on formulating inks with conductive, semiconductive, magnetic, piezoresistive, and piezoelectric properties. Here, a detailed landscape view on different droplet-based printing technologies (inkjet, aerosol jet, and electrohydrodynamic jet) is provided, with comprehensive discussion on their working principals. This is followed by a detailed research overview of different functional inks (metal, carbon, polymer, and ceramic). Different sintering methods and common substrates being used in printed electronics are also discussed, followed by an in-depth review of different physical sensors fabricated by droplet-based techniques. Finally, the challenges facing the field are considered and a perspective on possible ways to overcome them is provided.

PVDF-BaTiO3 Nanocomposite Inkjet Inks with Enhanced ß-Phase Crystallinity for Printed Electronics.

Polyvinylidene difluoride (PVDF) and its copolymers are promising electroactive polymers showing outstanding ferroelectric, piezoelectric, and pyroelectric properties in comparison with other organic materials. They have shown promise for applications in flexible sensors, energy-harvesting transducers, electronic skins, and flexible memories due to their biocompatibility, high chemical stability, bending and stretching abilities. PVDF can crystallize at five different phases of α, ß, γ, δ, and ε; however, ferro-, piezo-, and pyroelectric properties of this polymer only originate from polar phases of ß and γ. In this research, we reported fabrication of PVDF inkjet inks with enhanced ß-phase crystallinity by incorporating barium titanate nanoparticles (BaTiO3). BaTiO3 not only acts as a nucleating agent to induce ß-phase crystallinity, but it also improves the electric properties of PVDF through synergistic a ferroelectric polarization effect. PVDF-BaTiO3 nanocomposite inkjet inks with different BaTiO3 concentrations were prepared by wet ball milling coupled with bath ultrasonication. It was observed that the sample with 5 w% of BaTiO3 had the highest ß-phase crystallinity, while in higher ratios overall crystallinity deteriorated progressively, leading to more amorphous structures.

Impact of low-x resummation on QCD analysis of HERA data.

Fits to the final combined HERA deep-inelastic scattering cross-section data within the conventional DGLAP framework of QCD have shown some tension at low x and low Q 2 . A resolution of this tension incorporating ln ( 1 / x ) -resummation terms into the HERAPDF fits is investigated using the xFitter program. The kinematic region where this resummation is important is delineated. Such high-energy resummation not only gives a better description of the data, particularly of the longitudinal structure function F L , it also results in a gluon PDF which is steeply rising at low x for low scales, Q 2 ≃ 2.5 GeV 2 , contrary to the fixed-order NLO and NNLO gluon PDF.