The frequency-response behaviour of flexible piezoelectric devices for detecting the magnitude and loading rate of stimuli

Piezoelectric sensors with good flexibility and high sensitivity have attracted extensive interest in wearable electronics. Here, we report a novel frequency-response behaviour of piezoelectric voltage of a sensor that is based on a piezoelectric enhanced composite film of P(VDF-TrFE) and BaTiO3. The piezoelectric voltage enhances with the increase of frequency and becomes stable beyond the critical frequency. Such a demonstrated sensing characteristic of the piezoelectric sensor depends on the inner resistance of the voltmeter, which is determined by whether the loading of stimuli can be completed within the period of piezoelectric voltage measurement in the testing circuit. By utilizing the frequency-response behaviour in different frequency ranges, the flexible piezoelectric device exhibits excellent capabilities to quantitatively detect the magnitude and loading rate of stimuli. As a proof-of-concept demonstration, a flexible pressure sensor is successfully integrated with a bionic bee to monitor the flight status (i.e., strain rate and strain) of the vibrating wings. This work demonstrates that flexible piezoelectric sensors have great prospects for application in the field of bionic flying robots, thus paving the way forward for the development of smart self-sensing flexible electronics.