Ferroelectret nanogenerators were recently introduced as a promising alternative technology for harvesting kinetic energy. Here we report the device’s intrinsic properties that allow for the bidirectional conversion of energy between electrical and mechanical domains; thus extending its potential use in wearable electronics beyond the power generation realm. This electromechanical coupling, combined with their flexibility and thin film-like form, bestows dual-functional transducing capabilities to the device that are used in this work to demonstrate its use as a thin, wearable and self-powered loudspeaker or microphone patch. To determine the device’s performance and applicability, sound pressure level is characterized in both space and frequency domains for three different configurations. The confirmed device’s high performance is further validated through its integration in three different systems: a music-playing flag, a sound recording film and a flexible microphone for security applications.

This paper presents the design, modeling, calibration, and hysteresis compensation of a self-sensing precision stage used for active vibration isolation. The stage prototype is monolithically fabricated from the spring steel by wire electrical discharge machining process. Aiming to achieve an extremely compact structure, we design and fabricate a self-sensing actuator called smart piezo stack which is capable of not only generating high-resolution displacement but also monitoring the dynamic characteristics of the proposed stage. By means of the finite-element analysis and experimental measurements, we reveal and quantitatively analyze the crosstalk phenomenon in the smart piezo stack. After calibrating the sensitivity of the smart piezo stack experimentally, the dynamics model of the proposed stage is established. Furthermore, a nonlinear autoregressive moving average with exogenous inputs model based on backpropagation neural network is proposed to design a nonlinear controller based on adaptive inverse control. The intelligence of the developed controller allows the hysteresis in the stage which results from the embedded smart piezo stack to be directly compensated for without dynamics modeling in advance. Experimental validation of the adaptive inverse controller is conducted and the results demonstrate the effectiveness of the proposed mechanism and the developed control system.

Recent advances in precision manufacturing technology and a thorough understanding of the properties of piezoelectric materials have made it possible for researchers to develop innovative microrobotic systems, which draw more attention to the challenges of utilizing microrobots in areas that are inaccessible to ordinary robots. This review paper provides an overview of the recent advances in the application of piezoelectric materials in microrobots. The challenges of microrobots in the direction of autonomy are categorized into four sections: mechanisms, power, sensing, and control. In each section, innovative research ideas are presented to inspire researchers in their prospective microrobot designs according to specific applications. Novel mechanisms for the mobility of piezoelectric microrobots are reviewed and described. Additionally, as the piezoelectric micro-actuators require high-voltage electronics and onboard power supplies, we review ways of energy harvesting technology and lightweight micro-sensing mechanisms that contain piezoelectric devices to provide feedback, facilitating the use of control strategies to achieve the autonomous untethered movement of microrobots.