3D-printed heel-conformal wearable piezo-triboelectric hybrid sensor for self-powered discrimination of human locomotion

We report a 3D-printed heel-conformal wearable piezo-triboelectric hybrid sensor (PTHS) that vertically stacks a piezoelectric sensor (PS) and a triboelectric sensor (TS) on a heel-shaped substrate obtained by 3D scanning and printing. The PS comprises five stacked PVDF-TrFE nanofiber mats with average fiber diameters of 450 nm reinforced by 750 μm conductive solder bead arrays and consolidated by vacuum hot-press packaging, whereas the TS integrates a PVDF-TrFE nanofiber negative layer, a 10 μm PDMS charge-trapping transition layer, and an Al-film positive layer. Under foot-tapping at approximately 440 kPa, the PTHS produced peak-to-peak signals of about 12 V (PS) and 65 V (TS) with the intended sequential TS-then-PS activation.Across walking, jumping, and weight-shifting, the two channels generated distinguishable signal patterns, including a tenfold PS enhancement under high-impact jumping and selective PS-only activation during weight shifting, demonstrating the PTHS as a wearable platform for self-powered discrimination of human locomotion.