Fig. 2: Neuromodulation validation in vitro.

a Experimental setup (right) and schematic diagram (left) for measuring the US-driven electrical output of the ferroelectret in ethanol. b Voltage output measured in ethanol at a distance of 10 mm from an US probe to the ferroelectret, with a US setup of 1 MHz and 0.5 W cm⁻². c Schematics illustrating ex vivo experiments of ferroelectret implanted in a porcine tissue and visualizing the ___location of an implanted ferroelectret in porcine tissue. d Voltage generated by the ferroelectrets implanted at 1 cm, 5 cm, and 10 cm under the porcine tissue. e A schematic of the electrophysiological setup for voltage recording. Voltage change of animal tissue fluid was measured when US pulses were applied to the suspended ferroelectret in animal tissue fluid. f, g Voltage outputs yielded from air-blowing fibers, composite fibers, and ferroelectret fibers, respectively. n = 7 independent samples for each group. Data are expressed as mean values ± SD. All error bars indicate ± SD. ***P < 0.001. Air-blowing fibers/Composite fibers: P = 6.4439E-25; Composite fibers/Ferroelectret fibers: P = 2.5102E-32. P values are evaluated through one-sided ANOVA and post-Tukey analysis. h Ferroelectret fibers activated by US pulses yield local potentials that alter the membrane potential and/or the configuration of membrane receptors and results in opening of the Ca²⁺ channels. Ins3P, inositol trisphosphate. PLC, phospholipase C. i Light microscope image showing cells tightly adhered to the fibers. n = 8 independent experiments showing similar results. j The fluorescence images of the cells preincubated with Fluo-4 AM (membrane-permeable and Ca²⁺-dependent dye) on the ferroelectret fibers. Green, Ca²⁺. n = 8 independent experiments showing similar results. k Relative Ca²⁺ levels of cells on air-blowing fibers, composite fibers, and ferroelectret fibers, respectively. Data are expressed as mean values ± SD. All error bars indicate ± SD. n = 8 independent samples for each group. ***P < 0.001. US alone/Ferroelectret fibers: P = 2.1786E-9; Air-blowing fibers/Ferroelectret fibers: P = 3.4096E-9; Composite fibers/Ferroelectret fibers: P = 9.3635E-9. P values are evaluated through one-sided ANOVA and post-Tukey analysis.