Harvesting mechanical energy is an important route in obtaining cost-effective, clean and sustainable electric energy. Here we report a two-dimensional planar-structured triboelectric generator on the basis of contact electrification. The radial arrays of micro-sized sectors on the contact surfaces enable a high output power of 1.5 W (area power density of 19 mW cm À 2 ) at an efficiency of 24%. The triboelectric generator can effectively harness various ambient motions, including light wind, tap water flow and normal body movement. Through a power management circuit, a triboelectric-generator-based power-supplying system can provide a constant direct-current source for sustainably driving and charging commercial electronics, immediately demonstrating the feasibility of the triboelectric generator as a practical power source. Given exceptional power density, extremely low cost and unique applicability resulting from distinctive mechanism and structure, the triboelectric generator can be applied not only to self-powered electronics but also possibly to power generation at a large scale.

The grain refinement of 2-8 wt.% Y addition in as-cast Mg-Y binary alloys has been investigated. The results show that the microstructure of as-cast Mg-Y alloys consists of α-Mg matrix and Mg24Y5phase. Mg24Y5can become the effective nucleation core of α-Mg, and refine the grain size of the alloys. The ultimate tensile strength of as-cast Mg-5Y alloy is 180MPa at room temperature. Mg-5Y alloy can be a basis for developing light structural materials.

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