A triboelectric nanogenerator (TENG) facilitates the advancement of self-powered displacement sensors, which are important for many autonomous intelligent microsystems. However, the amplitude-based displacement sensing of conventional TENG-based sensors still suffers significantly from varying charge densities in harsh environments. Benefiting from the combination of intelligent signal processing algorithms and direct-current TENG sensors, this study proposes an environmentally robust character-based displacement sensing method that eliminates the influences of varying charge density in principle. The experimental results show that under drastically changing air humidity and other harsh environments, the sensing of threshold and maximum displacement has far superior consistency and stability than that of traditional amplitude-based TENG sensors, providing a novel route to realize reliable self-powered displacement sensing in environment-variable applications.

the urgent challenges of continuously increased demand for energy, the most commonly utilized energy source, fossil fuel, is limited and can lead to an energy crisis and severe environmental pollution. Alternative methods, such as green energy including solar, [1] wind, [2] and tide energy [3] that harvest various natural energy to solve the energy crisis, might suffer from a strong dependence on specific conditions and have large and complex equipment.Triboelectric nanogenerator (TENG), portability, [4,5] cost-effectiveness, [6,7] and high-efficiency [8,9] energy harvesting device, has become important milestone in the development of energy harvesting. [10,11] Based on the energy harvesting mechanisms of contact electrification and electrostatic charge induction, various mechanical energy can be converted into electricity. [12] In particular, TENG can convert energy from human motion [13,14] (walking, running, and stretching), [15,16] vibration, [17,18] wind, [19,20] rotating tires, [21] and flowing water, [22,23] which may solve the energy crisis by harnessing the widely distributed natural energy. [24][25][26] The energy harvesting system using TENG can harness natural kinetic energy under specific conditions. [27][28][29] While in the practical application, humidity (i.e., water) greatly eliminates the energy harvesting efficiency. [30,31] In principle, water inevitably impacts the dielectric proproteins of the triboelectric material within TENG and leads to output degradation, which limits TENG's application as a stable energy choice. Given that the movement of the ubiquitously existing water can be artificially controlled, if the triboelectrification energy of water droplets can be harvested properly, it may solve the challenge of the humidity impact on TENG theoretically. Thus, the emerging droplet-based power generators (DEG), one type of TENG, have gradually become the cutting-edge application for stable and robust electricity generation. Based on the significant triboelectric effect between the water and the triboelectric material, [32,33] the energy generated by a single water droplet can light multiple LEDs. [34,35] The DEG may fill the urgent needs for the future energy crisis. [36,37] Here, we summarized the recent research progress of DEGs and their application in energy harvesting. We have provided Electricity is the basic and essential need for every single person and guarantees the development of society, industry, and the economy. The limited conventional fossil fuel meets the challenge of the sharply increasing demand, while may lead to severe pollution. Emerging green energy harvesting systems can convert ambient kinetic, thermal, and solar energy to electricity effectivity. In this review paper, the authors provide an overview of the new and emerging methods, droplet-based electricity generators, that convert energy from the ubiquitously existing water droplets. The authors begin with a brief introduction of the working principle for droplet-based power generators. Existing configurations of...

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