Fig. 7

Mechanical flexible tube-type liquid-interactive ferroelectric sound device. a Sound pressure level (SPL) values of an liquid-interactive ferroelectric sound (LIFS) alternating current (AC) device as a function of the bending radius. Hydrogel was used as a liquid for the flexibility test. A photograph of a flexible device with the bending radius of 4 mm under measurement is shown in the inset. b Schematic of a rolled tube-type LIFS AC device. The device was fabricated by rolling a planar-type LIFS AC device five times, as shown in the schematics of the cross-sectional view of the device. The diameter and thickness of the tube were ~2 mm and 30 μm, respectively. c A photograph of the rolled tube-type LIFS AC device. Sound amplitude monitored with time when deionised water was passed through the tube. d Schematic of the fabrication of a tube-type LIFS AC device with attachable in-plane Cu electrodes. e Photographs of the tube-type LIFS AC device with attachable in-plane electrodes. The attachable electrodes facilitated in situ monitoring of a liquid at three different positions A, B, and C. Sound amplitude monitored with time at the positions A, B, and C of the photographs. All the devices were operated at the AC frequency and voltage of 20 kHz and 100 V, respectively