Figure 2.

The piezoelectric nanogenerator in the form of direct coupling to ocean waves. (a) A flexible device coating with piezoelectric paint for harvesting wave energy. Ocean Engineering, reprinted with permission from [15]. (b) A multifunctional system capable of both power generation and seawater desalination. Reprinted with permission from [26]. (c) Waterproof piezoelectric wave energy harvester. Reprinted with permission from [27]. (d) A novel wave energy conversion device consisting of twin piezoelectric wafers that were flexibly clamped at both ends. Reprinted with permission from [28]. (e) A buoyant water wave energy converter by integrating a piezoelectric fiber composite. Reprinted with permission from [29]. (f) An eel-inspired current energy harvesting device. Reprinted with permission from [30].