Flexible PVDF based piezoelectric nanogenerators

Piezoelectric materials are widely referred to as "smart" materials because they can transduce mechanical pressure acting on them to electrical signals and vice versa. They are extensively utilized in harvesting mechanical energy from vibrations, human motion, mechanical loads, etc., and converting them into electrical energy for low power devices. Piezoelectric transduction offers high scalability, simple device designs, and high-power densities compared to electro-magnetic/static and triboelectric transducers. This review aims to give a holistic overview of recent developments in piezoelectric nanostructured materials, polymers, polymer nanocomposites, and piezoelectric films for implementation in energy harvesting. The progress in fabrication techniques, morphology, piezoelectric properties, energy harvesting performance, and underpinning fundamental mechanisms for each class of materials, including polymer nanocomposites using conducting, non-conducting, and hybrid fillers are discussed. The emergent application horizon of piezoelectric energy harvesters particularly for wireless devices and self-powered sensors is highlighted, and the current challenges and future prospects are critically discussed.

Piezoelectric Materials for Energy Harvesting and Sensing Applications: Roadmap for Future Smart Materials

With the increase of interest in the application of piezoelectric polyvinylidene fluoride (PVDF) in nanogenerators (NGs), sensors, and microdevices, the most efficient and suitable methods of their synthesis are being pursued. Electrospinning is an effective method to prepare higher content β-phase PVDF nanofiber films without additional high voltage poling or mechanical stretching, and thus, it is considered an economically viable and relatively simple method. This work discusses the parameters affecting the preparation of the desired phase of the PVDF film with a higher electrical output. The design and selection of optimum preparation conditions such as solution concentration, solvents, the molecular weight of PVDF, and others lead to electrical properties and performance enhancement in the NG, sensor, and other applications. Additionally, the effect of the nanoparticle additives that showed efficient improvements in the PVDF films was discussed as well. For instance, additives of BaTiO3, carbon nanotubes, graphene, nanoclays, and others are summarized to show their contributions to the higher piezo response in the electrospun PVDF. The recently reported applications of electrospun PVDF films are also analyzed in this review paper.

A Review of Piezoelectric PVDF Film by Electrospinning and Its Applications

Boosting piezoelectric response of PVDF-TrFE via MXene for self-powered linear pressure sensor

Polyvinylidene fluoride (PVDF) is among the most attractive piezo-polymers due to its excellent piezoelectricity, lightweight, flexibility, high thermal stability, and chemical resistance. PVDF can exist under different forms of films, membranes, and (nano)fibers, and its piezoelectric property related to its β phase content makes it interesting for energy harvesters and wearable applications. Research investigation shows that PVDF in the form of nanofibers prepared by electrospinning has more flexibility and better air permeability, which make them more suitable for these types of applications. Electrospinning is an efficient technique that produces PVDF nanofibers with a high β phase fraction and crystallinity by aligning molecular dipoles (–CH2 and –CF2) along an applied voltage direction. Different nanofibers production techniques and more precisely the electrospinning method for producing PVDF nanofibers with optimal electrospinning parameters are the key focuses of this paper. This review article highlights recent studies to summarize the influence of electrospinning parameters such as process (voltage, distance, flow rate, and collector), solution (Mw, concentration, and solvent), and ambient (humidity and temperature) parameters to enhance the piezoelectric properties of PVDF nanofibers. In addition, recent development regarding the effect of adding nanoparticles in the structure of nanofibers on the improvement of the β phase is reviewed. Finally, different methods of measuring piezoelectric properties of PVDF nanofibrous membrane are discussed.

https://www.mdpi.com/2073-4360/13/2/174/pdf

Electrospun PVDF Nanofibers for Piezoelectric Applications: A Review of the Influence of Electrospinning Parameters on the β Phase and Crystallinity Enhancement.

Enhanced piezoelectric performance of BiCl3/PVDF nanofibers-based nanogenerators

The invention relates to a method for preparing an oriented porous polyvinylidene fluoride piezoelectric film, and belongs to the technical field of novel material preparation. The method includes uniformly dispersing Fe3O4 nanometer magnetic particles in polyvinylidene fluoride solution to form polyvinylidene fluoride composite solution; placing the polyvinylidene fluoride composite solution in magnetic fields and forming films by means of tape casting; inducing the Fe3O4 nanometer magnetic particles by the magnetic fields to aggregate to form uniformly oriented cones; inducing polyvinylidenefluoride beta phase by the nanometer magnetic particles to be crystallized and arranged on the surfaces of the cones in an orientation manner along with volatilization of solvents and forming Fe3O4/PVDF (polyvinylidene fluoride) composite films; drying the Fe3O4/PVDF composite films and then removing the Fe3O4 nanometer magnetic particles by diluted hydrochloric acid to obtain the oriented porouspolyvinylidene fluoride piezoelectric film. The method has the advantages that the method aims to overcome the shortcomings of incapability of implementing high beta crystalline phase transformation,incapability of arranging beta crystalline phase in an ordered orientation manner and poor flexibility of obtained piezoelectric films in the prior preparation art; the method is easy to operate andhas low requirements on preparation conditions and equipment, and the oriented porous polyvinylidene fluoride piezoelectric film prepared by the aid of the method is flexible and is high in piezoelectric constant and energy conversion coefficient.

Oriented porous polyvinylidene fluoride piezoelectric film and method for preparing same

The invention relates to an electrostatic spinning nozzle, and particularly relates to an electrostatic spinning nozzle making one-dimensional solid nano materials arranged in fiber in the axial direction of the fiber. The electrostatic spinning nozzle is composed of a liquid inlet, an abdominal cavity and a nozzle body, the abdominal cavity is composed of an upper cavity and a lower cavity, the inner wall face of the upper cavity is in a columnar shape, the inner wall face of the lower cavity is in an arc shape, and the nozzle body is located at the lower end of the lower cavity; the upper cavity and the lower cavity are in threaded connection, the liquid inlet is formed in the upper end face of the upper cavity, and the center axis of the liquid inlet and the center axis of the upper cavity are consistent with the center axis of the lower cavity and the center axis of the nozzle body. The electrostatic spinning nozzle is excellent in mechanical property, and the problem that the one-dimensional solid nano-materials cannot be distributed along the fiber in the spinning process can be solved. The electrostatic spinning nozzle is characterized in that the one-dimensional solid nanomaterials are arranged along the electrostatic spinning nano fiber. The electrostatic spinning nozzle is reasonable in design, simple in structure, integrally manufactured, low in cost and convenientto detect, maintain and clean.

Chen Chong

Papers

Enhanced piezoelectric performance of BiCl3/PVDF nanofibers-based nanogenerators

Oriented porous polyvinylidene fluoride piezoelectric film and method for preparing same

Electrostatic spinning nozzle