Confined Polymeric Nanowires Into Porous Alumina Matrix as Composite Piezoelectric Membrane for Sensing Applications (original) (raw)
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Distributed array of polymeric piezo-nanowires through hard-templating method into porous alumina
2011
We report on the preparation of ferroelectric polymeric nanowires through hard-templating strategy. Wet-impregnation of poly(vinylidene fluoride) (PVDF) and its copolymer poly(vinylidene fluoride-tri fluoro ethylene) [P(VDF TrFE)] was performed into commercially available porous Anodic Alumina Membrane (AAM). The polymeric nanowires show a diameter ranging from 144 to 166 nm, a length of tenth of micron and a high filling ratio of the alumina pores. X-ray diffraction pattern and infrared spectroscopy show the crystallization of both polymers into the ferroelectric β phase. In addition, Curie temperature (T c ) tests show an increase to higher T c for the PVDF-TrFE polymeric nanowires with respect to the bulk polymeric material, thus revealing the importance of confined crystallization into mono-dimensional structures. A piezoelectric behavior was also observed by a voltage generation upon mechanical pressure, without pre-poling or mechanically orienting the polymer. These crystalline piezoelectric nanowires distributed in a vertical array would potentially address applications like mechanical pressure sensors, e.g., in robotics.
Nanoconfinement: an Effective Way to Enhance PVDF Piezoelectric Properties
ACS Applied Materials & Interfaces, 2013
The dimensional confinement and oriented crystallization are both key factors in determining the piezoelectric properties of a polymeric nanostructured material. Here we prepare arrays of one-dimensional polymeric nanowires showing piezoelectric features by template-wetting two distinct polymers into anodic porous alumina (APA) membranes. In particular, poly(vinylidene fluoride), PVDF, and its copolymer poly(vinylidene fluoride-trifluoroethylene), PVTF, are obtained in commercially available APA, showing a final diameter of about 200 nm and several micrometers in length, reflecting the templating matrix features. We show that the crystallization of both polymers into a ferroelectric phase is directed by the nanotemplate confinement. Interestingly, the PVDF nanowires mainly crystallize into the β-phase in the nanoporous matrix, whereas the reference thin film of PVDF crystallizes in the α nonpolar phase. In the case of the PVTF nanowires, needle-like crystals oriented perpendicularly to the APA channel walls are observed, giving insight on the molecular orientation of the polymer within the nanowire structure. A remarkable piezoelectric behavior of both 1-D polymeric nanowires is observed, upon recording ferroelectric polarization, hysteresis, and displacement loops. In particular, an outstanding piezoelectric effect is observed for the PVDF nanowires with respect to the polymeric thin film, considering that no poling was carried out. Current versus voltage (I−V) characteristics showed a consistent switching behavior of the ferroelectric polar domains, thus revealing the importance of the confined and oriented crystallization of the polymer in monodimensional nanoarchitectures.
Preparation, characterization and sensor properties of ferroelectric and porous fluoropolymers
Proceedings. 11th International Symposium on Electrets
Ferroelectric copolymers of vinylidene fluoride and trifluoroethylene [P(VDF/TrFE)] have a strong piezoelectric and pyroelectric effect with a high potential for sensor and transducer applications. Porous polytetrafluoroethylene [PTFE] exhibits excellent electret properties and is suitable for transducer applications based on its macroscopic piezoelectricity. In this work the preparation of piezoelectric P(VDF/TrFE) films onto flexible as well as on any shaped printed circuits done through a spray technique from the polymer solution is reported. Results on array sensors, measuring dynamic pressure in air flow field monitoring as well as dynamic force measurements are presented. Electret transducers made by porous PTFE are prepared and their sensor properties are described.
Nanostructured piezoelectric polymers
Journal of Applied Polymer Science, 2014
Among the wide variety of piezoelectric materials available, polymers offer an interesting solution because of their high mechanical flexibility, easy processing, and conformable features; they maintain good ferroelectric and piezoelectric properties. The most prominent examples of these are poly(vinylidene fluoride) (PVDF) and its copolymer, poly(vinylidene difluoride-trifluoroethylene) [P(VDF-TrFE)]. An attractive prospective consists of the preparation of nanostructured polymers. It has been shown that the dimensional confinement of such macromolecules down to the nanoscale can improve their piezoelectric properties because the tailoring of the chemical structure is performed at the molecular level. In this review, we show how nanostructured polymers can be obtained and discuss reports on the ferroelectric and piezoelectric properties of nanostructured PVDF and P(VDF-TrFE) materials. In particular, we show how dimensional confinement leads to piezoelectric nanostructures with relevant performances, with a focus on the macromolecular structural arrangement that enhances their behavior. Experimental results and applications are also reported to compare the performances of different nanostructuration processes and the polymer efficiencies as piezoelectric materials.
Nanoscale Fabrication of the Ferroelectric Polymer Poly
2012
Thin films of an organic ferroelectric system, poly(vinylidene fluoride with trifluoroethylene) P(VDF-TrFE, Kureha Corporation, Tokyo, Japan) 75:25 layers, have been deposited on highly ordered pyrolytic graphite and silicon dioxide by the horizontal Schaefer method of Langmuir-Blodgett techniques. It is possible to "shave" or mechanically displace small regions of the polymer film by using atomic force microscope nanolithography techniques such as nanoshaving, leaving swaths of the surface cut to a depth of 4 nm and 12 nm exposing the substrate. The results of fabricating stripes by nanoshaving two holes close to each other show a limit to the material "stripe" widths of an average of 153.29 nm and 177.67 nm that can be produced. Due to the lack of adhesion between the substrates and the polymer P(VDF-TrFE) film, smaller "stripes" of P(VDF-TrFE) cannot be produced, and it can be shown by the sequencing of nanoshaved regions that "stripes" of thin films can be removed. Keywords dip-pen; nanolithography; nanoshaving; atomic force microscope (AFM); poly(vinylidene fluoride with trifluoroethylene); ferroelectric; nanostructures; lithography; nanotechnology engineering may well be possible, in spite of the fact that these materials are "soft." Poly(vinylidene fluoride with trifluoroethylene) (PVDF) and its copolymers are fluoropolymers with monomer chains of (-CH 2-CF 2-) and exhibit piezoelectric, pyroelectric, and ferroelectric properties and have excellent stability to chemicals, mechanical flexibility, and biocompatibility. This unique combination of properties makes P(VDF-TrFE) a good candidate for sensor, storage, and actuator elements, especially in harsh and biological environments (Clark et al., '92; Gu et al., '94; Clark et al., '92a). In order to realize the full
Sensing Ability of Ferroelectric Oxide Nanowires Grown in Templates of Nanopores
Materials, 2020
Nanowires of ferroelectric potassium niobate were grown by filling nanoporous templates of both side opened anodic aluminum oxide (AAO) through radiofrequency vacuum sputtering for multisensor fabrication. The precise geometrical ordering of the AAO matrix led to well defined single axis oriented wire-shaped material inside the pores. The sensing abilities of the samples were studied and analyzed in terms of piezoelectric and pyroelectric response and the results were compared for different length of the nanopores (nanotubes)—1.3 µm, 6.3 µm and 10 µm. Based on scanning electronic microscopy, elemental and microstructural analyses, as well as electrical measurements at bending and heating, the overall sensing performance of the devices was estimated. It was found that the produced membrane type elements, consisting potassium niobate grown in AAO template exhibited excellent piezoelectric response due to the increased specific area as compared to non-structured films, and could be fur...
Different Scale Confinements of PVDF-TrFE as Functional Material of Piezoelectric Devices
IEEE Sensors Journal, 2000
The effect of micro and nanostructuration on the piezoelectric properties of polymeric samples was studied in the present work. We prepared micro-sized pillars and nano-wires (thus one-dimensional structures) of a piezoelectric polymer Poly(VinyliDene Fluoride-Tri FluoroEthylene) PVDF-TrFE and we compared their structural and piezoelectrical properties with a thin film (thus two-dimensional) of the same material. X-ray diffraction and infrared spectroscopy measurements showed that the crystallization of the polymer into the ferroelectric β-phase is affected by the size of the confinement. The piezoelectric characterization of the three polymeric structures showed important improvements as far as the nanostructuration is reached. Application as tactile sensor devices is therefore under development.
Journal of Physical Chemistry C, 2018
Poly(vinylidene fluoride-trifluoroethylene), P(VDF-TrFE), microstructures have been produced using different solvents, including green ones, by different techniques, such as solvent casting, screen-printing, replica molding, electrospray, and electrospinning. The obtained microstructures span from simple porous and dense films to spheres, fibers, and patterned three-dimensional architectures, with no significant variation in their physicochemical and electrical properties. The simplicity, low cost, and reproducibility of the processing techniques allied to their versatility to adapt to other materials to produce controlled and tailored microstructures with specific properties demonstrate their potential in a wide range of technological applications, including biomedical, energy storage, sensors and actuators, and filtration.