A triboelectric rolling ball bearing with self-powering and self-sensing capabilities

With the popularization of the Internet of Things (IoT) and big-data technology, the requirement for intelligent rolling bearings has grown exponentially. In this paper, a novel intelligent rolling bearing, called triboelectric rolling ball bearing (TRBB), with self-powering and self-sensing capabilities is proposed. The structure of a mechanical rolling bearing is directly adopted for the TRBB, and a triboelectric nanogenerator with rolling free-standing mode is devised by pasting flexible interdigital electrodes on the outer ring of the TRBB. On the premise of maintaining the structural integrity of the rolling bearings, direct contact between the electrodes and rolling balls is avoided, and the service life of the TRBB can thus be guaranteed. Because of the contact electrification between the rolling ball and outer ring, electricity is generated when the TRBB supports the rotor and rotates. The electrical output characteristics of the TRBB are measured at different rotating speeds, and the peak power with optimal load resistance is found. The root mean square value and frequency of output current are employed as the two rotational speed indicators. Design parameters, such as those of cage, structural dimensions, ball material and outer ring material, are analyzed to investigate their effects on the sensitivity of the TRBB. Rotating speed curves obtained using the two indicators are compared with those of a commercial sensor. Two abnormal states, rolling ball missing and electrode breakage, are considered to assess other self-sensing capabilities of the TRBB. Tests for continuous running and different rotor weights are carried out to illustrate the durability and stability of the TRBB, respectively. Tests on load capacitance charging and driving of low-power devices are also conducted to analyze the self-powering capability of the TRBB. This work presents a multi-functional self-powering and self-sensing system, wherein the fabricated TRBB has widespread application prospects in the development of IoT.