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. I n certain embodiments, the grating structures of the second electrode grid 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. The triboelectric sensor may comprise a cover layer formed over the first and/or second electrode grids. I n certain embodiments, the substrate is flexible. The electrodes may be formed from a conductive polymer material. For example, the conductive polymer material may comprise a hydrogel PDMS elastomer. Also disclosed herein is a triboelectric control system comprising a motion control interface, said motion control interface comprising at least one triboelectric sensor as disclosed herein. The motion control interface may comprise at least one further triboelectric sensor configured to detect motion in a single direction, such that motion detected by the triboelectric sensor and the further triboelectric sensor is translatable into a movement control signal in three dimensions. The further triboelectric sensor may comprise an elongate substrate having an electrode at each end. The elongate substrate may be formed from an elastic material. The elastic material may be silicone rubber, for example. The triboelectric control system may comprise: