Flexible, ultra-wideband acoustic device for ultrasound energy harvesting and passive wireless sensing

As a promising means of energy transmission and communication, acoustic devices with flexibility and wideband are always urgently required. Here, we developed a flexible, ultra-wideband triboelectric ultrasonic device (FUTUD). Benefiting from the low mechanical quality factor of an ultra-thin PI substrate and interlocking nanostructures (of the order of micro-strain or nano-strain), the bandwidth of the FUTUD reached up to 10 MHz, which is currently unprecedented in the study of triboelectric acoustic devices. Based on the wideband properties of the FUTUD, we proposed two application strategies. For low-frequency ultrasound (20–200 kHz), the FUTUD acted as an ultrasound energy harvester that converted acoustic energy into electrical energy to power implantable electronic devices in vivo. It could generate a voltage of 1.2 V and a current of 150 μA through porcine tissue of 10 mm thickness and charge a capacitor at a rate of 8.4 μC/s up to 3.2 V. For high-frequency ultrasound (0.2–10 MHz), the FUTUD was integrated with a flexible electromagnetic coil to transmit electrical signals containing physiological information from in vivo to ex vivo wirelessly as a passive wireless sensor. This research shows great promise for the development of intelligent and miniaturized implantable medical devices.