# A Self-Powered Basketball Training Sensor Based on Triboelectric Nanogenerator
###### Abstract  
During the basketball training for beginner children, sensors are needed to count the number of times the basketball hits the target area in a certain period of time to evaluate the training effect. This study proposes a self-powered basketball training sensor, based on a triboelectric nanogenerator. The designed sensor with a rectangular floor shape will output a pulse signal with the same frequency as the basketball impact to achieve the measurement function through the mutual contact of the internal copper (Cu) and polytetrafluoroethylene (PTFE). Test results show that the working frequency of the sensor is 0 to 5 Hz, the working environment temperature should be less than 75\({}^{\circ}\)C, the working environment humidity should be less than 95%, and which has high reliability. Further tests show that the maximum output voltage, current, and power of the sensor can reach about 52 V, 4 uA, and 26.5 uW with a 10 M\(\Omega\) resistance in series, respectively, and the output power can light up 12 light-emitting diode (LED) lights in real-time. Compared with the traditional statistical method of manual observation, the sensor can automatically count data in a self-powered manner, and also can light up the LED lights in real-time as an indicator of whether the basketball impacts the target area, to remind beginner children in real-time. t  
Footnote †: journal: Applied  
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Footnote †: journal: Applied  
In addition, if the sensor used for detection is powered by batteries, the frequent batteries replacement will cause the sensor to be taken out multiple times, which will undoubtedly increase labor intensity. On the other hand, if cables are used to power the sensor, cables must be laid during the construction of the basketball stadium, which will increase construction costs and have potential safety hazards. Therefore, sensors with the self-powered function will undoubtedly be more suitable for basketball training environments. For self-powered sensors, the current results on power generation methods, including piezoelectric generators, electromagnetic generators and solar nano-antennas [4], etc., can solve the power supply problem of the sensor, but the basketball training grounds for children are not exposed to sunlight because the training venues are generally indoor gymnasiums, and the costs of piezoelectric and electromagnetic power generation are relatively higher, so other self-powered methods may be more suitable for indoor basketball training conditions. Figure 1: Composition and working principle. (**a**) Schematic diagram of “bounce the ball in situ” and “two-hand chest pass the ball”; (**b**) schematic diagram of the sensor structure; (**c**) schematic diagram of the sensor working steps. PTFE, polytetrafluoroethylene. Fortunately, the triboelectric nanogenerator brings hope to solve the above-mentioned problems. The triboelectric nanogenerator with a basic principle of triboelectricity and electrostatic induction [5] was proposed in 2012 [6], and has been widely used in the fields of energy harvesting and sensors. For example, in the field of energy harvesting, the triboelectric nanogenerator can collect low-frequency and low-density weak energy, and theoretically can convert most of the physical energy into electrical energy, so it had been widely used in biological energy harvesting [7; 8], rainwater energy harvesting [9; 10], vibration energy harvesting [11; 12; 13], wave energy harvesting [14; 15; 16], environmental mechanical energy harvesting [17], and wind energy collection [18; 19], etc. On the other hand, in the field of sensors, sensors based on triboelectric nanogenerators have a self-powered function, so it had been widely used in areas where traditional power supply methods are inefficient, such as human physiological monitoring [20; 21; 22], vibration monitoring [23; 24], wind monitoring [25; 26], acceleration monitoring [27], sports monitoring [28; 29; 30], force or pressure monitoring [31; 32; 33], and speed monitoring [34; 35], etc.