Self-retracting triboelectric-electromagnetic hybrid sensor for high-precision displacement and speed monitoring

Self-powered sensors have become pivotal in the era of Internet of Things (IoT). However, triboelectric nanogenerator (TENG)-based self-powered sensors usually encounter challenges in practical applications due to the instability of their output signals, particularly the susceptibility of signal amplitude to environmental factors. Herein, a self-retracting triboelectric-electromagnetic hybrid nanogenerator (SRTE-HNG) via rotating and stretching is designed to achieve high-precision displacement and speed measurement. Basically, the SRTE-HNG comprises a stator and a rotor, the triboelectricity and electromagnetic electricity will be generated simultaneously via stretching of a fluorinated ethylene propylene (FEP) film that drives the rotor. The triboelectric signals are used for displacement measurement, while the electromagnetic signals provide the speed feedback through periodic variations, as a result, the complementary of the two effects significantly improves the sensor’s accuracy and stability. The SRTE-HNG consistently outputs high-quality signals under various stretching lengths and speeds, achieving maximum V_oc of 520 V and I_sc of 6 mA for TENG and EMG, respectively. In terms of sensing performance, the TENG demonstrates displacement and velocity sensitivities of 2.79 V mm⁻¹ and 10.62 V (cm/s)⁻¹, while the EMG shows sensitivities of 0.033 mA mm⁻¹ and 0.13 mA (cm/s)⁻¹. Both exhibit a linearity exceeding 0.99 and a response time of 19 ms. This shows SRTE-HNG excels in energy harvesting and self-powered sensing, providing an efficient, reliable solution for future smart sensing systems and wearables.