One dimensional lead-free (K,Na)NbO3 nanostructures for a flexible self-powered sensor

Abstract

Lead-free (K,Na)NbO₃ (KNN) nanorods (NRs), which have a relatively high piezoelectric response and good environmental compatibility, are expected to be used in the application fields of sensors, actuators, etc. In the present study, flexible composite devices with piezoelectric KNN nanostructures were successfully fabricated as a flexible and cost-effective strain sensor. The composition-controlled KNN nanorods (NRs) were synthesized via the molten salt reaction, while piezoresponse force microscopy (PFM) was utilized to characterize the three-dimensional (3-D) morphology as well as the piezoelectric properties of single crystalline KNN nanorods. Then, the KNN NR-polydimethylsiloxane (PDMS) films were fabricated through the tape casting process, and assembled into the self-powered sensor with Cu-coated polyethylene terephthalate (PET) substrates. The as-fabricated KNN–PDMS sensor was affected by the pressing and releasing activities of the human body, and the output voltage was measured concurrently. As a result, the strain sensor obtains an output signal of ∼0.5 V with KNN NR fillers of 0.5 vol% in PDMS, which implies that KNN NRs are promising in the application of lead-free flexible sensor devices.