Flexible piezoelectric nanofiber composite membranes as high performance acoustic emission sensors

• A flexible acoustic emission sensor based on PZT nanofibers was fabricated.
• The electromechanical coupling effect was found to increase up to 370% after polarization.
• The anisotropic sensitivity was observed in the attenuation maps.
• The sensor offers the benefits of small size, high flexibility, high sensitivity and low cost for monitoring structures.

A flexible acoustic emission (AE) sensor based on lead zirconate titanate (PZT) nanofiber composite membrane is described. The PZT nanofibers, with diameters varying from 50 nm to 120 nm, were electrospun and aligned across interdigitated electrodes. After being packaged in a flexible polymer structure with a thickness of ∼5 μm, this small scale AE sensor can bend freely to follow curved surfaces or embedded into structures. High piezoelectric voltage constant, flexibility and mechanical strength of PZT nanfibers result in a high performance of the demonstrated AE sensor. Fundamental characterization indicates a spontaneous polarization of the PZT nanofibers without any polarization treatment. The electromechanical coupling effect was increased up to 370% after 90 min of polarization under an external electric field of ∼3 V/μm. The anisotropic sensitivity, which can reduce the required number of sensors to indentify the location of the AE source, was observed from the attenuation maps. The small scale, flexible and highly sensitive PZT nanofiber AE sensor opens up new applications for monitoring small scale structures, curved surfaces and even living cells.