Enhanced Piezoelectricity of Electrospun Polyvinylidene Fluoride Fibers for Energy Harvesting

Piezoelectric polymers are promising energy materials for wearable and implantable applications for replacing bulky batteries in small and flexible electronics. Therefore, many research studies are focused on understanding the behavior of polymers at a molecular level and designing new polymer-based generators using polyvinylidene fluoride (PVDF). In this work, we investigated the influence of voltage polarity and ambient relative humidity in electrospinning of PVDF for energy-harvesting applications. A multitechnique approach combining microscopy and spectroscopy was used to study the content of the β-phase and piezoelectric properties of PVDF fibers. We shed new light on β-phase crystallization in electrospun PVDF and showed the enhanced piezoelectric response of the PVDF fiber-based generator produced with the negative voltage polarity at a relative humidity of 60%. Above all, we proved that not only crystallinity but also surface chemistry is crucial for improving piezoelectric performance in PVDF fibers. Controlling relative humidity and voltage polarity increased the d33 piezoelectric coefficient for PVDF fibers by more than three times and allowed us to generate a power density of 0.6 μW·cm-2 from PVDF membranes. This study showed that the electrospinning technique can be used as a single-step process for obtaining a vast spectrum of PVDF fibers exhibiting different physicochemical properties with β-phase crystallinity reaching up to 74%. The humidity and voltage polarity are critical factors in respect of chemistry of the material on piezoelectricity of PVDF fibers, which establishes a novel route to engineer materials for energy-harvesting and sensing applications

Enhanced Piezoelectricity of Electrospun Polyvinylidene Fluoride Fibers for Energy Harvesting.

Piezoelectric polymers are promising energy materials for wearable and implantable applications for replacing bulky batteries in small and flexible electronics. Therefore, many research studies are focused on understanding the behavior of polymers at a molecular level and designing new polymer-based generators using polyvinylidene fluoride (PVDF). In this work, we investigated the influence of voltage polarity and ambient relative humidity in electrospinning of PVDF for energy-harvesting applications. A multitechnique approach combining microscopy and spectroscopy was used to study the content of the β-phase and piezoelectric properties of PVDF fibers. We shed new light on β-phase crystallization in electrospun PVDF and showed the enhanced piezoelectric response of the PVDF fiber-based generator produced with the negative voltage polarity at a relative humidity of 60%. Above all, we proved that not only crystallinity but also surface chemistry is crucial for improving piezoelectric performance in PVDF fibers. Controlling relative humidity and voltage polarity increased the d33 piezoelectric coefficient for PVDF fibers by more than three times and allowed us to generate a power density of 0.6 μW·cm-2 from PVDF membranes. This study showed that the electrospinning technique can be used as a single-step process for obtaining a vast spectrum of PVDF fibers exhibiting different physicochemical properties with β-phase crystallinity reaching up to 74%. The humidity and voltage polarity are critical factors in respect of chemistry of the material on piezoelectricity of PVDF fibers, which establishes a novel route to engineer materials for energy-harvesting and sensing applications

Enhanced Piezoelectricity of Electrospun Polyvinylidene Fluoride Fibers for Energy Harvesting.

Piezoelectric polymers are promising energy materials for wearable and implantable applications for replacing bulky batteries in small and flexible electronics. Therefore, many research studies are focused on understanding the behavior of polymers at a molecular level and designing new polymer-based generators using polyvinylidene fluoride (PVDF). In this work, we investigated the influence of voltage polarity and ambient relative humidity in electrospinning of PVDF for energy-harvesting applications. A multitechnique approach combining microscopy and spectroscopy was used to study the content of the β-phase and piezoelectric properties of PVDF fibers. We shed new light on β-phase crystallization in electrospun PVDF and showed the enhanced piezoelectric response of the PVDF fiber-based generator produced with the negative voltage polarity at a relative humidity of 60%. Above all, we proved that not only crystallinity but also surface chemistry is crucial for improving piezoelectric performance in PVDF fibers. Controlling relative humidity and voltage polarity increased the d33 piezoelectric coefficient for PVDF fibers by more than three times and allowed us to generate a power density of 0.6 μW·cm-2 from PVDF membranes. This study showed that the electrospinning technique can be used as a single-step process for obtaining a vast spectrum of PVDF fibers exhibiting different physicochemical properties with β-phase crystallinity reaching up to 74%. The humidity and voltage polarity are critical factors in respect of chemistry of the material on piezoelectricity of PVDF fibers, which establishes a novel route to engineer materials for energy-harvesting and sensing applications

Novel drug delivery systems based on triaxial electrospinning based nanofibers

Electrospinning is a widely investigated process for forming nanofibers. Nanofibers in drug delivery systems are extensively tested due to its remarkable properties e.g. small pore size or large surface area. Recent articles have informed about formation of fibers using triaxial electrospinning in drug delivery systems. This paper summarizes the process of triaxial electrospinning and its application in drug delivery. Triaxial electrospinning has advantages in forming complex nanostructures for specific drug delivery applications. This paper summarizes the possibility to use triaxial electrospinning to resolve the problem of limited drug solubility, to protect biomolecules from hostile environment, and to control drug release kinetics, with the possibility of loading of various drugs. There are literature data evidencing the possibility to achieve sustained release with a border case of zero rate order kinetics. There is no doubt that triaxial electrospinning opens a new way to develop sophisticated nanomaterials for achieving the desired functional performances and to expand the applications in the drug delivery area. Triaxial electrospinning method is interdisciplinary area with great potential in nanotechnology.Scopu

Influência da estrutura de diferentes copolímeros de etileno e a-olefinas na funcionalização com anidrido maleico Influence of structure of ethylene a-olefins copolymers in functionalization with maleic anhydride

A funcionalização de copolímeros de etileno e a-olefinas com anidrido maleico (AM) foi realizada em solução de xileno com peróxido de dibenzoíla (DBP) como iniciador. Foi estudado o efeito das diferentes estruturas dos copolímeros, como número e comprimento de ramificação, na incorporação do AM. A funcionalização também foi realizada em estado fundido utilizando-se um misturador Rheomix 600 e uma extrusora Rheocord 9000 da Haake. A funcionalidade foi determinada por titulometria de neutralização e os produtos foram caracterizados por espectroscopia na região do infravermelho (FT-IR) e por cromatografia de permeação em gel (GPC). A funcionalidade dos copolímeros de etileno com 1-hexeno aumentou com o aumento do teor de comonômero e dos copolímeros com 1-octeno e 1-deceno aumentou com o aumento do teor de a-olefina até um máximo, decrescendo e mantendo-se constante.<br>Chemical modification of ethylene a-olefins copolymers with maleic anhydride was studied by radical reaction in solution, melt mixing and extrusion. The effect of copolymer structure, as the amount and length of the branches, was evaluated on the MA incorporation. The reactions were also achieved in Rheomix 600 (Haake) mixer and Rheocord 9000 (Haake) extruder. Functionalization was determinated by titration and modified ethylene a-olefins copolymers were characterized by Infrared Spectroscopy and Gel Permeation Chromatography. The maleic anhydride incorporation in the ethylene-hexene copolymers increases with the amount of a-olefin. Functionalization of ethylene-octene and ethylene-decene comonomers increases with increasing peroxide concentration until a maximum and then decreases up to a constant value