Measurement of the d31 piezoelectric coefficient of compliant materials by non-contact polarization and resonant signal enhancement

An apparatus for the measurement of converse piezoelectric coefficient in transversal direction (d31) is developed for testing of compliant materials in form of stripes, wires, or thin films. The measurement is not invasive, since it does not require to metallize or contact the sample with conductive electrodes, therefore it can be conveniently applied to nanostructured polymeric devices, like for instance electrospun nanofiber meshes. Low values of piezoelectric coefficients can be detected by exploiting an amplification method based on a mechanical resonance. Piezoelectric coefficients can be determined quantitatively thanks to a suitable calibration method, not depending on the spring constant of the sample.