Magnetized joystick with dual-anisotropy for high-capacity wearable human-machine interactions.

One of the urgent demands for flexible and wearable sensors is to achieve single-channel, less-sensor, and multi-output for effective communications. However, expansion of signal capacity on a single interface often requires sensor arrays, which significantly increases the complexity in electrode layout and multiple device design. In this work, we developed a flexible magnetized joystick (FMJ) with structurally induced eigenfrequency anisotropy by applying laser cutting process to a raw magnetized cubic. Using an eigenfrequency-polarity dual-anisotropy addressing method, we show that single FMJ can achieve four identifiable outputs based on the direction of in-plane mechanical inputs. According to the cantilever beam model, the eigenfrequency library can be expanded by adjusting cutting parameters, dimensions, and material properties, laying the foundation for further expanding signal capacity through the combination of multiple FMJs. The advantages of FMJs in terms of high capacity and multi-functionality are demonstrated through a range of human-machine interaction (HMI) applications, including game control, PowerPoint slides, robot car control, and a fingertip calculator. The increased signal requirement would not impose the complexity of electrical connection thanks to the interference-free parallel design of the electrodes. We expect that the development strategy will provide valuable insights for further advancement of high-capacity wearable HMI.