Beyond Metallic Electrode: Spontaneous Formation of Fluidic Electrodes from Operational Liquid in Highly Functional Droplet-Based Electricity Generator.

The droplet-based electricity generator (DEG) has facilitated efficient droplet energy harvesting, yet diversifying its applications necessitates the incorporation of various to the DEG. This study first proposes a methodology for advancing the DEG by substituting its conventional metallic electrode with electrically conductive water electrode (WE), which is spontaneously generated during the operation of the DEG with operating liquid. Due to the inherent conductive and fluidic nature of water, the introduction of the WE maintains the electrical output performance of the DEG while imparting functionalities such as high transparency and flexibility. So, the resultant WE applied DEG (WE-DEG) exhibits high optical transmittance (≈99%) and retains its electricity-generating capability under varying deformations, including bending and stretching. This innovation expands the versatility of the DEG, and especially, a sun-raindrop dual-mode energy harvester is demonstrated by hybridizing the WE-DEG and photovoltaic (PV) cell. This hybridization effectively addresses the weather-dependent limitations inherent in each energy harvester and enhances the temperature-induced inefficiencies typically observed in PV cells, thereby enhancing the overall efficiency. The introduction of the WE will be poised to catalyze new developments in DEG research, paving the way for broader applicability and enhanced efficiency in droplet energy harvesting technologies.

Advancing Energy Harvesting Efficiency from a Single Droplet: A Mechanically Guided 4D Printed Elastic Hybrid Droplet-Based Electricity Generator.

A droplet possesses the ubiquity and potential to harvest a vast amount of energy. To exploit droplets effectively, a novel output enhancement strategy that can coexist and create synergy with the recently studied droplet-based electricity generator (DEG) and material/surface structure modification must be investigated. In this study, a mechanical buckling-based 4D printed elastic hybrid droplet-based electricity generator (HDEG) consisting of a DEG and solid-solid triboelectric nanogenerator (S-S TENG) is first presented. During the electricity generation process of the DEG by droplet impact, the HDEG structure, which is merged via a simple 4D printing technique, permits the conversion of dissipated energy into elastic energy, resulting in an S-S TENG output. The HDEG outputs are naturally integrated owing to the simultaneous activation of a single droplet, resulting in an approximately 30% improvement over the output of a single DEG. Internal and external parametric studies are performed as HDEG design guidelines. The HDEG exhibits a 25% better energy supply performance than that of a single DEG, demonstrating its applicability as a power source. This research proposes the way toward a hybrid system that efficiently harvests energy from ubiquitous droplets.