Structure modification of 0–3 piezoelectric ceramic/polymer composites through dielectrophoresis

Abstract

Anisotropic material properties can be induced in ceramic-polymer composites by applying an alternating electric field of moderate strength during processing. Under suitable conditions, particles of a ceramic filler material that are randomly dispersed in a liquid polymer or pre-polymer can be polarized and they then exhibit a collective response to localised gradients in the electric field. Typically the particles experience a mutually attractive force which causes them to form 'pearl-chains' or columnar structures spanning the gap between electrodes. If the fluid is solidified, for example by curing the polymer resin, then the newly formed structures can be fixed in place to produce a composite with directional electrical and mechanical properties. Direct visual observations were made for low volume fraction dispersions of pure lead titanate in an epoxy pre-polymer under the influence of an electric field. The observed interaction was correlated with low-field dielectric measurements and existing theory to identify optimum assembly conditions. The dielectric properties of the fluid are predominant and the formation of chain-like structures is found to be both field strength and field frequency dependent. The dielectric permittivities of a range of structurally modified composites were measured and compared with existing theoretical models of di-phasic materials.

Flexible Piezoelectric Touch Sensor by Alignment of Lead‐Free Alkaline Niobate Microcubes in PDMS

“…composites. This value is more than one order of magnitude higher than that obtained for randomly dispersed particle composites [17][18][19][20][21][22][23][24][25][26][31][32][33][34][35] and on par with the values reported for the piezoelectric polymers PVDF and P(VDF-TrFE). [14][15][16] The explanation for the increase in g 33 is that d 33 strongly depends on the intra-chain connectivity, while ε r is a bulk property, proportional to the fill factor but almost independent of the microstructure.…”

“…[22][23][24] Aligned composite films have been reported with piezoelectric voltage coefficients attaining 120 mV m N -1 . [25,26] The Curie temperature remains, in first order approximation, that of the ceramic filler.…”

Dielectrophoretically structured piezoelectric composites with high aspect ratio piezoelectric particles inclusions

“…Chains which are free to move (i.e., not bound to one of the electrodes) are attracted towards other chains during later stages of the dielectrophoresis process; a phenomenon seen before in DEP processed composites. 24 The average orientation angleh and relative average chain length,L L max , as a function of time for a typical experiment are represented in Figure 6. Here, L max is defined as the length of the microscope image in the direction of the electric field.…”

Piezoelectric and mechanical properties of structured PZT–epoxy composites

“…[9][10][11][12][13][14][15] It is demonstrated that dielectrophoresis can be used for structuring of PZT particles as columns in a polymer matrix, resulting in composites with quasi 1-3 connectivity. [16][17][18][19] This will keep the manufacturing process as simple as 0-3 composites, and consequently, production costs can be kept low. In dielectrophoresis, when a moderate electric field is applied across a suspension of ferroelectric particles in an insulating medium, the particles orient themselves toward the direction of applied electric field.…”