Piezoelectric coaxial filaments produced by coextrusion of poly(vinylidene fluoride) and electrically conductive inner and outer layers

Abstract

The development of new thermoplastic polymer-based piezoelectric sensors with filament geometry is described. These filaments are appropriate for integration into textiles and provide new possibilities in the design and development of low-cost flexible sensors produced at high rates. The developed three-layered piezoelectric monofilaments have been produced by coextrusion using poly(vinylidene fluoride) and two different polypropylene-based electrically conductive polymers. Filaments with about 800-mm diameter, producing electrical signals proportional to the mechanical deformation applied, were obtained. The signal output has been found adequate for straightforward use with conventional piezoelectric signal conditioning systems. One of the conductive polymers tested allowed better filament geometry and process stability. This article describes the coextrusion production process and the results obtained in the electromechanical tests performed.

Piezoelectric Flexible LCP–PZT Composites for Sensor Applications at Elevated Temperatures

“…Coaxial filament based piezoelectric sensors with piezoactive polymers, e.g. P(VDF-TrFE) and PVDF, with copper filament with thin layer of conductive materials and conductive inner and outer layers have achieved pressure sensitivity of 30-380 mv to applied pressure of 0-2 kPa and piezoelectric coefficient d1r 2.78-3.59 pC/N measured through charge amplifier, respectively [14][15]. Other types of printed structures, such as PVDF-tourmaline [16] have achieved sensitivities of 1.72-2.06 V with impact test of falling object of 1.02 kg at height of 0.05 m, that equals to 6.7 kPa pressure.…”

“…In addition, the other type of filaments reported mostly utilize piezo-active PVDF-blends or ABS that have relative low melting temperature of ≤ 180 C [14][15][16][17]23]. Thus, making them unsuitable for high temperature sensor applications above 200 C. The depoling and Curie temperatures of such materials are even lower (roughly 100 C), thus the applicability for sensing at elevated temperatures is even more limited.…”

“…Even though feasible piezoelectric materials for various forms of 3D printing is still under development, e.g. different coextruded and metal core structures, and films utilizing PVDF as a matrix material have been developed [14][15][16][17], these are not suitable in some cases. Also, the matrix materials used in these structures are not proper for high temperatures due to relative low melting and heat deflection temperatures (HDT) of piezoelectric polymers.…”

Processing and Electrical Response of Fully Polymer Piezoelectric Filaments for E-Textiles Applications

“…The production processes and poling methods for this arrangement have also been previously studied, in particular with respect to the study of the influence of the conductive layers on the piezoelectric properties of the PVDF [9][10][11]. Comprehensive work by Lund et al [10] and Ferreira et al [11] have shown for twolayered filaments that the electroactive phase content is not affected by the conductive inner core.…”

Piezoelectric microstructured fibers via drawing of multimaterial preforms

“…More importantly, the piezoelectric fiber retained its performance even after three days' cyclic bend-release tests. Compared to other piezoelectric fibers [20][21][22][23]28 , the fibers presented in this work feature a swiss roll structure of the piezoelectric layer, which considerably increases the active surface area and reduces the layer thickness, this resulting in considerably higher voltages and currents (and consequently electric powers) that can be generated by such fibers. Large-area piezoelectric textiles could be fabricated by incorporating the drawn fibers into woven fabrics, thanks to their excellent mechanical properties (as they are made only of plastics), and the use of low-cost, high volume fabrication techniques (fiber drawing).…”