Enhanced piezoelectricity from highly polarizable oriented amorphous fractions in biaxially oriented poly(vinylidene fluoride) with pure β crystals

Huang, Yanfei; Rui, Guanchun; Li, Qiong; Allahyarov, Elshad; Li, Ruipeng; Fukuto, Masafumi; Zhong, Gan‐Ji; Xu, Jia‐Zhuang; Li, Zhong‐Ming; Taylor, Philip L.; Zhu, Lei

doi:10.1038/s41467-020-20662-7

Cited by 95 publications

(113 citation statements)

References 32 publications

(61 reference statements)

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“…Recent work demonstrated a substantial contribution of the amorphous phase to the measured total piezoelectric effect. [37,38] Katsouras et al found electromechanical coupling of crystalline and amorphous phases resulting in an additive contribution to the piezoelectric coefficient d 33 . [37] The amorphous phase in the present work amounts to ≈40% of the film volume.…”

Section: Mechanical Switching Mechanismmentioning

confidence: 99%

Mechanical Nanoscale Polarization Control in Ferroelectric PVDF‐TrFE Films

Roth

Koch

Rata

et al. 2022

Adv Elect Materials

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Ferroelectric polymer films offer strong advantages like mechanical flexibility, biocompatibility, optical transparency, and low‐cost processing. However, their dielectric or piezoelectric performance is often inferior to that of oxide ferroelectric materials. Key to the dielectric or piezoelectric performance of semicrystalline polymers is the enhancement of electric dipolar order that is naturally lower than in crystalline ferroelectrics. Here, reorientation and alignment of the electric polarization in thin films by the mechanical effect of a scanning unbiased force microscopy tip is demonstrated as a versatile tool for nanoscale domain writing. Thin films (50–150 nm) of PVDF‐TrFE (78:22) on graphite are prepared with dense (110)‐oriented β‐phase lamellae randomly oriented in the film plane. The in‐plane polarization can be poled “mechanically” along any deliberately chosen direction in the film plane after vertical electric poling. Domain patterns with resolution down to ≈50 nm are written with four (out of six possible) local polarization orientations. Written domains show excellent long‐time stability. The surface roughening from the mechanical treatment is moderate (rms roughness of 2–3 nm). A ferroelastic origin of the mechanical polarization switching is discussed. Finally, suggestions are made how to utilize the domain patterns in thin film devices.

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Section: Mechanical Switching Mechanismmentioning

confidence: 99%

Mechanical Nanoscale Polarization Control in Ferroelectric PVDF‐TrFE Films

Roth

Koch

Rata

et al. 2022

Adv Elect Materials

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“…Figure 6a−f compares the dielectric properties measured at room temperature for all layered films and control films. To quantitatively analyze the dielectric properties, theoretical dielectric values are also calculated by a series model by assuming the absence of interfaces: (10) where ε* is the complex permittivity function of the layered dielectrics, which includes the real part ε′and imaginary part ε″ through a relation ε* = ε′ − iε″. 43 The same relation holds for ε A *and ε B *of component A and B layers.…”

Section: Resultsmentioning

confidence: 99%

“…As for the important applications in electric devices, multilayer films containing polyvinylidene fluoride (PVDF) or its copolymers have aroused sustained interest because of their interesting electroactive properties when used as sensors, actuators, and energy storage and energy-harvesting devices. , As well documented, PVDF has a higher electrical moment per unit cell of up to 8 × 10 –30 C·m originating from the strong electronegativity of fluorine atoms that renders the outstanding dielectric, piezoelectric, pyroelectric, and ferroelectric properties. − However, in practical applications (e.g., electrostatic capacitors), PVDF exhibits the higher dielectric loss associated with the bulk conductivity (∼10 –9 S/m) and ferroelectric switching of dipoles in the crystalline phases, which is even much higher than the biaxially oriented polypropylene (BOPP) films despite the higher dielectric constant K of 10–12. − This drawback could cause Ohmic heating to decrease the lifetime of electronic devices and thus limit the practical applications. Fortunately, the multilayer assembly of PVDF with low- K polymers, such as polycarbonate (PC), , polysulfone (PSF), and poly(ethylene terephthalate) (PET), has been developed as a reliable approach to fabricate multilayer structured dielectrics with desired performance.…”

Section: Introductionmentioning

confidence: 99%

Roles of Interlayer Diffusion and Confinements in Manipulating Microstructural Evolutions in Multilayer Assembled Polyvinylidene Fluoride/Poly(methyl methacrylate) Films for Tunable Dielectric and Piezoelectric Performances

Zhao

Zhang

et al. 2021

ACS Appl. Polym. Mater.

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We present the multilayer assembly of polyvinylidene fluoride (PVDF)/poly(methyl methacrylate) (PMMA) films through a continuous and scalable layer-assembly process, where the effects of interlayer diffusion and confinements are highlighted. It is found that interlayer diffusion and confinements are strongly dependent on the layer compositions and sizes, which significantly govern the evolutions of the layer architecture and microstructure in the assembled films. Interlayer diffusion driven by the entropic advantage stabilizes the layered morphology in spite of the viscoelastic contrast between components. The overall crystallinity in confined PVDF layers is suppressed by the improved geometrical confinement with the reduction in layer thicknesses and/or by the enhanced molecular confinement with the increase in the fraction of PMMA. Meanwhile, an increasingly favorable formation of an electroactive β-phase is identified particularly for PVDF-rich films. Specifically, the crystallinity of the β-phase reaches around 25% for PVDF/PMMA (75/25) composition. The molecular origin for the β-phase is attributed to the intense stretching that induces the chain conformation of all-trans zigzag during layer assembly. In addition, the dielectric constant of films reaches a higher level of ∼30 depending on the fraction of the β-phase and molecular orientations that evolved from the multilayered assembly. Intriguingly, the piezoelectric output voltage and current, respectively, reach 7.4 V and 0.7 μA and demonstrate the tunable energy-harvesting capability. Both dielectric and piezoelectric performances for these films are found to be mainly contributed by the polarizations of β-phase crystals, where the interlayer diffusion, layer compositions, and sizes further influence significantly those electric responses by governing the charge transport across layers. Mechanisms for these electric responses are further clarified. Our work clearly reveals how the interlayer diffusion and confinements manipulate the microstructure evolutions under real micro-/nanolayer assembly processing conditions in order to up-scale PVDF-based multilayer films for lightweight and flexible capacitors and piezoelectric nanogenerators for electronic devices.

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“…Nevertheless, the polar crystalline β‐phase exists in all‐ trans (TTTT) conformation, which provides the polymer with the largest dipole moment per unit cell, and thus the highest piezoelectric response. Various methods, including mechanical stretching, high‐electric field and electrospinning, have been explored to develop β‐phase enriched PVDF films 13–15 . These high‐energy methods are expensive and time‐consuming.…”

Section: Introductionmentioning

confidence: 99%

Microfluidic fabrication of β‐phase enriched poly(vinylidene fluoride) microfibers toward flexible piezoelectric sensor

Meng

et al. 2022

Journal of Polymer Science

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β‐phase enriched piezoelectric poly(vinylidene fluoride) (PVDF) films/fibers are often prepared by high‐energy costing methods, including mechanical stretching, high‐electric field or electrospinning. In this study, PVDF piezoelectric microfibers, for the first time, were prepared by microfluidic spinning technology. The β‐phase enriched PVDF microfibers with various diameters could be easily obtained inside the microfluidic channel due to the mass transfer induced phase inversion of the inner PVDF solution. The influence of diameter of the fibers, PVDF concentration of the inner phase and water content of the outer phase on the β‐phase content and crystallinity degree of the obtained fibers was studied in detail. The obtained β‐phase enriched fiber was weaved into meshes. Flexible piezoelectric fabrics were then developed based on these meshes, and further used as in‐situ and real time human motion monitoring. This simple and effective strategy provides a promising microfluidic spinning technique toward the development of functional microfibers and wearable piezoelectric sensors, which may also give some implies for the industrial wet‐spinning of piezoelectric PVDF fibers in the future.

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Enhanced piezoelectricity from highly polarizable oriented amorphous fractions in biaxially oriented poly(vinylidene fluoride) with pure β crystals

Cited by 95 publications

References 32 publications

Mechanical Nanoscale Polarization Control in Ferroelectric PVDF‐TrFE Films

Mechanical Nanoscale Polarization Control in Ferroelectric PVDF‐TrFE Films

Roles of Interlayer Diffusion and Confinements in Manipulating Microstructural Evolutions in Multilayer Assembled Polyvinylidene Fluoride/Poly(methyl methacrylate) Films for Tunable Dielectric and Piezoelectric Performances

Microfluidic fabrication of β‐phase enriched poly(vinylidene fluoride) microfibers toward flexible piezoelectric sensor

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