fig2
Figure 2. (A) S-HNG for powering small electronic devices. Used with permission[24]. Copyright 2009 Nanoscale. (B) Multi-DOF TENG with stacked layers and multiple resonant frequencies. Used with permission[26]. Copyright 2024 John Wiley and Sons. (C) Compact I-TENG for self-powered CO2 monitoring. Used with permission[25]. Copyright 2025 Elsevier. (D) S-TENG for efficient water-wave energy harvesting. Used with permission[43]. Copyright 2017 Elsevier.
