Novel properties of multi-poled piezoelectric network structures

We present the piezoelectric properties of multi-poled network microstructures based on cross, Gibson-Ashby and face-centred cubic base cells at a range of solid fractions and with different polarisation profiles. Piezoelectric properties are determined via computational homogenisation with the finite element method. Each polarisation profile is triple-poled, so it includes piezoelectric material poled in the x, y and z directions. The result of this is that the homogenised microstructures have fully non-zero piezoelectric coefficients and fully non-zero piezoelectric voltage constants. We show that the axial components of the effective voltage constant g (11), g (22), and g (33) can be vastly improved by ensuring struts are poled to match their orientation, so for example the piezoelectric material should be z-poled within a strut that is parallel to the z axis. We present novel extensions of commonly used figures of merit for single-poled piezoelectric materials that are relevant for the multi-poled case. We use these extended figures of merit to identify the network structures that have excellent piezoelectric properties for sensor and hydrophone applications. Furthermore, when varying the solid fraction of a given network microstructure, we show that the hydrostatic sensitivity of the meta-material increases as the acoustic impedance decreases. This property is unusual and near impossible to obtain using bulk material. Due to their highly sensitive piezoelectric response and full non-zero piezoelectric coefficients, such novel meta-materials could be utilised in next generation hydrophones, sensors, or other electromechanical devices.