control the 3D motions of the drone intuitively according to different finger sliding operations. First the eight directions with 0/1 coding electrodes are programmed to control the in-plane motions of the drone, i.e., forward, backward, left, right, left front direction, right rear direction, right front direction and left rear direction. The generated triboelectric signals from the interface 1200 and the square wave signals after the processing circuit 1310 for the eight directions are depicted in Figures 13(b-e). The corresponding finger sliding traces on the interface 1200 and drone motions in 3D space are also shown as insets. Then the right electrode pattern 1214 of seven strip electrodes with varying spacing is programmed to control the up/down motion of the drone when sliding up or down by finger. The top electrode pattern 1216 of six strip electrodes with varying spacing is programmed to control the in-plane rotation motion of the drone under left/right finger sliding. The generated triboelectric signals and the square wave signals for the up/down and in-plane rotation drone control are illustrated in Figures 13(f) and 13(g), together with the corresponding finger sliding traces and drone motions. I n addition to application in 3D control as described above, embodiments of the presently disclosed sensors may be used for other applications such as security code entry. For instance, 4 directions can be defined using two-bit coding electrodes, 8 directions can be defined using three-bit coding electrodes, 16 directions can be defined using four-bit coding electrodes, etc. I n one embodiment, an eight-direction 0/1-coding sensor may be adopted as the interface of a security code system. Two types of coding strategies may be implemented using the device, that is, a graphic code and a digital code, as depicted in Figures 14(a) and 15(a). In the graphic code system, each direction is only regarded as active or inactive. To set the code, one can select which direction is active and which direction is inactive. Then in order to trigger the code, one only needs to remember all the active directions and slide, regardless of the sliding order. Thus the graphic code is very straightforward and easy to remember, provides a fast response in both triggering and recognition, and importantly, requires no specific order of sliding. As long as one slides all the "set" active directions, the code is considered as correct. Figures 14(b,c) show a