Clamping effect on the piezoelectric responses of screen-printed low temperature PZT/Polymer films on flexible substrates

Abstract

Abstract. This paper introduces a new flexible PZT/polymer composite material that can be screen-printed onto fabrics and flexible substrates, and investigates the clamping effect of these substrates on the characterization of the piezoelectric material. Experimental results showed that the optimum blend of PZT/polymer binder with a weight ratio of 12:1 which provides a dielectric constant of 146. The measured value of the piezoelectric coefficient d 33 was found to depend on the substrate used. Measured d 33clp values of 70, 40, 36 pC/N were obtained from the optimum formulation printed on Polyester-cotton with an interface layer, Kapton and alumina substrates, respectively. The variation in the measured d 33clp values occurs because of the effect of the mechanical boundary conditions of the substrate. The piezoelectric film is mechanically bonded to the surface of the substrate and this constrains the film in the plane of the substrate (the 1-direction). This constraint means that the perpendicular forces (applied in the 3-direction) used to measure d 33 introduce a strain in the 1-direction that produces a charge of the opposite polarity to that induced by the d 33 effect. This is due to the negative sign of the d 31 coefficient and has the effect of reducing the measured d 33 value. Theoretical and experimental investigations confirm a reduction of 13%, 50% and 55% in the estimated freestanding d 33fs values (80 pC/N) on Polyester-cotton, Kapton and alumina substrates, respectively. These results demonstrate the effect of the boundary conditions of the substrate/PZT interface on the piezoelectric response of the PZT/polymer film and in particular the reduced effect of fabric substrates due to their lowered stiffness. IntroductionMechanical boundary conditions can affect the mechanical performance of the piezoelectric material and its measured piezoelectric response. This paper explores the effect of the substrate mechanical boundary condition on the measured properties of printed polymer piezoelectric films. The magnitude of this effect is dominated by the mechanical properties of the substrate and the influence of three different substrates (textile plus interface layer, Kapton and alumina) is presented. This enables a comparison between rigid ceramic, flexible polymer and flexible textile substrates.

Polymer-based smart materials by printing technologies: Improving application and integration

“…With the global requirements for increased efficiency, safety, low-cost, scalability, diminished materials waste, simple patterning and low production costs, printing technologies are very appealing for piezoelectric devices development 82,152,154 .…”

“…Thick films of BaTiO3 with 15µm were fabricated using Pt substrate and by screen-printing technique159 . Saturation polarization, coercive field and piezoelectric coefficient of the textured thick film were 7.5 μC.cm -2 , 2.9 kV.cm -1 and 136 pm.V -1 , respectively.Almusallam et al154 also presented a low temperature type PZT/PVDF with 0-3 connectivity composite produced using screen-printed process and flexible textiles. The optimal composition had a weight ratio of 12/1 (PZT/polymer), exhibiting a relative dielectric constant of 146 (at 1 kHz) and a maximum d33 of: 70 pC.N −1 for polyester-cotton, 40 pC.N −1 to Kapton and 36 pC.N −1 to alumina substrates.Such development on printed flexible piezoelectric materials is of particular and significant interest once it will enable suitable sensitive electronic systems, specially electronic skins that can be involved around a robot's body, prosthetic hands or even fabrication of piezoelectrics on large areas wafers cheaper than the standard commercially available.…”

Modeling and analysis of the effect of substrate on the flexible piezoelectric films for kinetic energy harvesting from textiles

“…44 However, the cotton and polyester are used commonly for flexible electronic devices. 46 The PVDF polymer layer was sandwiched between two silver electrodes that were used to enable film poling and perform study of different parameters (see Figure 4). The investigated textile substrates are polyester-cotton, cotton, and polyamide-imide (Kermel) where the weave chosen is plain (weft and warp direction).…”

“…. [43][44][45] In addition, Almusallam et al 46 presented an experimental study on clamping effect on the piezoelectric responses of screen-printed low-temperature PZT/polymer films on flexible substrates. Later, same authors 47 made a series of studies about the use of flexible piezoelectric nanocomposite films for kinetic energy harvesting from textiles.…”

Micromechanics-based prediction of the effective properties of piezoelectric composite having interfacial imperfections

“…Hence, various piezoelectric composites have been fabricated such as the lead zirconate titanate (PZT)-polymer composite (Almusallam et al, 2015;Venkatragavaraj et al, 2001) for an enhanced dielectric and hydrostatic piezoelectric coefficient and polyvinylidene difluoridein (PVDF)-SiC composite (Zhang et al, 2015;Zhou et al, 2015) for improved dielectric permittivity and elastic stiffness. Further, physical reinforcements as well as voids are known to improve some properties, i.e., the hydrostatic piezoelectric figure of merit increases with porosity (Zhang et al, 2017).…”