fig8

Figure 8. (A) 3D-wrapped wirelessly implantable ultrasound-driven electrical stimulation system based on PA and PU technologies^[73]. Reprinted with permission. Copyright 2021, Rsc Publishing; (B) PVDF/BZT-BCT@PDA thin-film nanogenerator for nerve stimulation^[74]. Reprinted with permission. Copyright 2021, Elsevier; (C) HENG-based vagus nerve stimulator^[76]. Reprinted with permission. Copyright 2021, Elsevier; (D) Ultrathin piezoelectret with sandwiched polymer structure with good implantability^[77]. Reprinted with permission. Copyright 2021, Elsevier; (E) H-UEH is based on multilayered piezoelectric electret based on air-hole arrays for nerve stimulation^[78]. Reprinted with permission. Copyright 2022, John Wiley and Sons. BZT-BCT: 0.5Ba(Zr_0.2Ti_0.8)O₃-0.5(Ba_0.7Ca_0.3)TiO₃; ECG: electrocardiography; FEP: fluorinated ethylene propylene; HENG: high-performance hydrogel nanogenerators; H-UEH: high-efficiency ultrasonic energy harvester; PA: photoacoustic; PDMS: polydimethylsiloxane; PDA: polydopamine; PU: piezo-ultrasound; PVA: poly(vinyl alcohol); PVDF: polyvinylidene fluoride.