Scalable Manufacture of All-Printed—Lead-Free Piezoelectric Sensors

The electromechanical transduction of vibrations via the piezoelectric effect provides essential information regarding the structural health of components across a wide range of industries, such as transportation, aerospace, and construction. Commercial piezoelectric sensors operating in the high-frequency regime utilize the ceramic lead zirconate titanate (PZT), but PZT is brittle and toxic. Furthermore, PZT requires high processing temperatures to maximize piezoelectric performance. In contrast, the biocompatible and printable polymer poly(vinylidene fluoride) (PVDF) possesses a low piezoelectric coefficient (30 pC/N). A novel class of ferroelectric materials based on organic-manganese and organic-iron halides possesses high piezoelectric coefficients (110-185 pC/N), processability from water and organic solvents, and multiple equivalent piezoelectric axes that enable observable piezoelectricity in printed polycrystalline films.

In turn, this has enabled the fabrication of all-printed piezoelectric sensors using interdigitated silver electrodes for applications in structural health monitoring. Highlights from this FlexTech-funded research include the electrohydrodynamic inkjet printing of high-resolution silver interdigitated electrodes to increase the sensor signal, processing insights used to optimize the printed piezoelectric layer, the development of a finite element model to extract the piezoelectric coefficient of printed, polycrystalline manganese- and iron-halide-based piezoelectrics. Roll-to-roll fabrication trials showcase the potential for high-throughput manufacture and commercialization of all-printed piezoelectric sensors.