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

Abstract

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, we propose a facile interfacial engineering approach based on amine-functionalized graphene oxide (AGO) to manipulate the intermolecular interactions in poly (vinylidenefluoride-trifluoroethylene) (PVDF-TrFE) to induce β-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 demonstrated voltage coefficient, energy density, and energy-harvesting figure of merit values of 0.30 Vm N -1 , 4.75 J cm -3 , and 14 pm 3 J -1 , respectively, making it outstanding compared with state-of-the-art ceramic-free ferroelectric films. We believe this work can open-up new insights towards 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.

Electrospun Micro/Nanofiber-Based Biomechanical Sensors

“…161 Incorporating an auxiliary layer within sensors can effectively regulate the contact state of internal relevant sensing structures to enhance their overall performance. 162,163 Huang et al 164 improved the sensitivity and the linear range of the flexible biomechanical sensor by introducing an electrospun gridded PU nanofiber as a spacer layer between the resistive material and electrode layer, which can attenuate the initial contact between the active layer and electrode layer, as well as slow down the flattening process of the active material surface. Both elevate the sensitivity and linear range of the resulting sensors (Figure 8A).…”

High-Fidelity sEMG Signals Recorded by an on-Skin Electrode Based on AgNWs for Hand Gesture Classification Using Machine Learning

“…The AgNWs are generally dispersed in solvents such as ethanol, deionized water, and isopropyl alcohol, which makes them easier to deposit on the substrate than other 1D nanomaterials such as carbon nanotubes, which exist in the powder state generally . The AgNWs are commonly deposited on the substrate to form the conductive layer by spin coating, Meyer rod scraping, drop casting, or spray coating in the previous reports. ,, For measurements of sEMG signals, the shape of the two measurement electrodes should preferably be strip-shaped and spaced about 20 mm to reduce the crosstalk from other surrounding muscle movements to obtain high quality signals. , Therefore, it is necessary to customize the AgNWs/PDMS hybrid electrode pattern for sEMG monitoring. A patterned AgNW/PDMS hybrid electrode was fabricated by the method of vacuum filtration, and the AgNWs were exposed on the PDMS surface rather than embedded, resulting in the unevenness of the entire skin-electrode interface .…”

“…60 The AgNWs are commonly deposited on the substrate to form the conductive layer by spin coating, 33 Meyer rod scraping, 34 drop casting, 56 or spray coating in the previous reports. 35,37,62 For measurements of sEMG signals, the shape of the two measurement electrodes should preferably be strip-shaped and spaced about 20 mm to reduce the crosstalk from other surrounding muscle movements to obtain high quality signals. 36,50 Therefore, it is necessary to customize the AgNWs/PDMS hybrid electrode pattern for sEMG monitoring.…”

Liquid Electrolyte-Assisted Electrospinning for Boosting Piezoelectricity of Poly (vinylidene Fluoride) Fiber Mats

“…Up to now, strategies such as copolymerization, , mechanical stretching, , dynamic-pressure or high-pressure crystallization, − ultrafast cooling, , electrospinning, − etc., have been reported to improve the β phase contents and dipole polarization. In addition, functional materials, like graphene oxide (GO), , MXene, , surface-functionalized carbon nanotubes, , organoclay, piezoelectric ceramics, − etc., are introduced to achieve piezoelectricity improvement through the interaction with dipoles of PVDF and its copolymers as well. For instance, Abdolmaleki et al reported that GO functionalized with amine groups (AGO) could improve the piezoelectric coefficient ( d 33 ) of annealed poly­(vinylidene fluoride-trifluoro ethylene) (PVDF-TrFE) films after casting by 27% at 0.1 wt % AGO .…”

“…In addition, functional materials, like graphene oxide (GO), , MXene, , surface-functionalized carbon nanotubes, , organoclay, piezoelectric ceramics, − etc., are introduced to achieve piezoelectricity improvement through the interaction with dipoles of PVDF and its copolymers as well. For instance, Abdolmaleki et al reported that GO functionalized with amine groups (AGO) could improve the piezoelectric coefficient ( d 33 ) of annealed poly­(vinylidene fluoride-trifluoro ethylene) (PVDF-TrFE) films after casting by 27% at 0.1 wt % AGO . In addition, Liu et al found that self-assembled PVDF/GO fibers with a core–shell structure fabricated by electrospinning showed an out-of-plane piezoelectric coefficient ( d 33 ) 426% improvement compared with conventional pure PVDF nanofibers .…”