Incorporating MIL-125 Metal-Organic Framework for Flexible Triboelectric Nanogenerators and Self-Powered Sensors for Robotic Grippers

Abstract

Triboelectric nanogenerators (TENGs) are getting popular as biomechanical energy harvesters to power small electronic devices and as self-powered sensors for pressure, motion, vibration, wind, waves, biomedical information, and chemical substance detections. In this study, the TENG is designed with biocompatible materials, and concentrations of its components have been optimized to generate higher power for application as an energy source and tactile sensor. The process involves using metal-organic frameworks (MOFs), namely MIL-125, with high charge-inducing and charge-trapping capabilities incorporated into the commercial Ecoflex matrix. Electrical characterization demonstrated that the sample with 0.25 wt% MIL-125 (0.25%MOF/Ecoflex) is the optimal concentration in the matrix with an output of up to 305 V and 13 µA, respectively. Moreover, the proposed flexible TENG converts mechanical energy to electrical, with a maximum power density of 150 µW cm⁻² (1.5 W m⁻²), which is more than twice superior to the pristine Ecoflex-based counterparts. The TENG shows robust and stable performance without noticeable degradation during continuous 200,000 cyclic testing. Furthermore, 0.25%MOF/Ecoflex TENG can power small electronic devices such as calculators, humidity sensors, and cardiac pacemakers. A robotic gripper trained via machine learning to identify various objects is also successfully developed with a self-powered 0.25%MOF/Ecoflex TENG sensor.