First proposed by Wang in 2012, the triboelectric nanogenerator (TENG, also called Wang generator) derived from Maxwell’s displacement current shows great prospect as a new technology to convert mechanical energy into electricity, based on the triboelectrification effect and electrostatic induction. TENGs present superiorities including light weight, cost-effectiveness, easy fabrication, and versatile material choices. The concept of harvesting blue energy using the TENG and its network was first brought out in 2014. As a new form of blue energy harvester, the TENG surpasses the EMG in that it intrinsically displays higher effectiveness under low frequency, owing to the unique feature of its output characteristics. Moreover, adopting the distributed architecture of light-weighted TENG networks can make it more suitable for collecting wave energy of high entropy compared with EMGs, which are oversized in volume and mass.
Covering over 70% of the earth’s surface, ocean plays a crucial role for lives on the planet and can be regarded as an enormous source of blue energy, whose exploitation is greatly beneficial for dealing with energy challenges for human beings . With extreme climate conditions taking place more frequently nowadays, the world feels the urge to take immediate action to alleviate climate deterioration caused by global warming . Carbon neutrality is thus put forward as a goal to reach balance between emitting and absorbing carbon in the atmosphere . One of the most effective methods is to develop and expand the use of clean energy that generates power without carbon emission, such as the enormous blue energy . Meanwhile, with the increasing activities in ocean, equipment deployed in the far ocean is facing problems regarding an in situ and sustainable power supply, where blue energy is an ideal source for developing new power solutions for such applications, allowing self-powered marine systems and platforms, though the harvesting scale can be much smaller .
The ocean blue energy is typically in five forms: wave energy, tidal energy, current energy, thermal energy, and osmotic energy, among which the wave energy is promising for its wide distribution, easy accessibility, and large reserves. The wave energy around the coastline is estimated to be more than 2 TW (1 TW = 10 12 W) globally . However, the present development of wave energy harvesting is challenged by its feature as a type of high-entropy energy, which refers to the chaotic, irregular waves with multiple amplitudes and constantly changing directions that are randomly distributed in the sea . Most significantly, wave energy is typically distributed in a low-frequency regime, yet the most common and classic method of blue energy harvesting at status quo, the electromagnetic generator (EMG), performs rather poorly in low-frequency energy harvesting, which relies on propellers or other complex mechanical structures to drive bulky and heavy magnets and metal coils in order to transform mechanical energy into electricity . Thus, it usually has high cost and low reliability.