A comfortable, FDM 3D-printed triboelectric insole for motion recognition and energy harvesting

Smart insoles show great potential for gait analysis and rehabilitation training. However, existing triboelectric nanogenerator (TENG)-based insoles often rely on complex fabrication processes or rigid components to achieve high performance. This compromises wearability and comfort. Here, we report a comfortable, highly elastic, and customizable triboelectric insole. It is fabricated using fused deposition modeling 3D printing with a commercial thermoplastic elastomer filament. The design integrates two independent TENG units at the forefoot and heel. This enables dual-zone plantar pressure sensing while enhancing overall elasticity. Through structural optimization guided by numerical simulations, a TENG unit configuration with an 80° slant angle and 2.0 mm wall thickness was established to balance electrical output, mechanical stability, and wearing comfort. The TENG units exhibit a linear open-circuit voltage response ranging from 3.35 to 45.83 V under applied forces of 10–200 N. They maintain stable performance after 10 000 loading cycles. The insole efficiently harvests biomechanical energy during natural walking. It can power 73 LEDs in a single step. Moreover, it effectively captures plantar pressure signals during human locomotion. By extracting multi-dimensional feature vectors and employing an optimized Gaussian-kernel Support Vector Machine, the system achieves a robust motion recognition accuracy of 96.12% even under varying environmental conditions. Overall, this work demonstrates strong application potential for human motion monitoring and biomechanical energy harvesting.