6. A triboelectric sensor according to claim 5, wherein the at least one grid structure comprises a second electrode grid formed on an opposite side of the substrate compared to the first electrode grid and configured to function as an output electrode of a second triboelectric nanogenerator operating under sliding single electrode mode; wherein the second electrode grid comprises a plurality of different grating structures disposed along different respective directions relative to a surface of the substrate such that different characteristic triboelectric-based output signals are detectable via the second electrode grid for sliding of the object along the different respective directions. configured to function as an output electrode of a first triboelectric nanogenerator operating under sliding single electrode mode; wherein the first electrode grid comprises a plurality of different grating structures disposed along different respective directions relative to a surface of the substrate such that different characteristic triboelectric-based output signals are detectable via the first electrode grid for sliding of the object along the different respective directions. 7. A triboelectric sensor according to claim 5, wherein the at least one grid structure comprises a second electrode grid that comprises a plurality of different grating structures that are modulated differently than the grating structures of the first electrode grid; and wherein the first and second electrode grids are connected to form a single electrode such that different characteristic triboelectric-based output signals are detectable via the single electrode. 8. A triboelectric sensor according to any one of claims 5 to 7, wherein the grating structures of the first electrode grid differ from each other in one or more of: the number of grating elements, the widths of the grating elements, and the sequence of the grating elements; and/or wherein the grating structures of the second electrode grid differ from each other in one or more of: the number of grating elements, the widths of the grating elements, and the sequence of the grating elements.