Fig. 2

Mechano-electric response properties of the ultrasound-powered hydrogels. Piezo-response amplitude hysteresis loops (a) and phase curves (b) of KBTO nanoparticles. (c) Quantitative piezo-response amplitude measures the effective longitudinal piezoelectric coefficient of KBTO. (d) Schematic diagram of crystal structure changes of KBTO nanoparticle under mechanical force. (e) Finite-element simulation of the potential distribution of KBTO nanoparticle with COMSOL with or without pressure generated by ultrasound cavitation. (f) Schematic diagram of ultrasound-powered hydrogel generating voltage under pressure. (g) Finite-element simulation of the potential distribution of 0.1KBGO hydrogel without external force and under a constant 10⁸ Pa force. (h) Schematic diagram of a laboratory-made piezoelectric voltage outputs test apparatus. (i) The output voltage of GO, 0.1BGO, 0.1KBGO, 0.5BGO, and 0.5KBGO hydrogels under ultrasonic stimulation with a sound intensity of 1 W/cm². (j) The output voltage of 0.1KBGO hydrogel under ultrasonic stimulation with different sound intensities of 0 to 2 W/cm² and the enlarged view under ultrasonic stimulation with a sound intensity of 1.5 W/cm²