To realize the high-efficiency acquisition of environmental mechanical energy,traditional triboelectric nanogenerators (TENGs) based on contact-separation consist of two separate triboelectric layers.Their large contact-separation gap increases the overall volume of the device,making it difficult to realize miniaturization and flexibility.This work,therefore,presents a fully enclosed all-in-one-shaped flexible TENG (FEAST) with an air cavity using rubber mixing and high-temperature vulcanization.The air pressure inside the enclosed air cavity facilitates effective contact-separation of the FEAST.The homogeneous integration between the triboelectric layer and the electrode layer enhances structural firmness without using extra spacer materials.The developed FEAST presents excellent mechanical durability even after 10000 cycles.By increasing the active contact area between the triboelectric materials,a maximum peak-peak output voltage,current,and power density of 130 V,1.1 μA,and 277 mW/m2,respectively,were obtained with an effective stress area of 1 cm2.Moreover,the fully enclosed structure ensures that the output performance is not affected by the external environment.The FEAST was fixed onto the sole of a shoe to demonstrate its applicability in harvesting mechanical energy from human motions.Overall,the developed method provides a simple approach for optimizing the structure of TENGs and is compatible with large-scale manufacturing.