Feature: LEDs
The proposed triboelectric nanogenerator can power 100 LEDs, simply by shaking it
Liquid-type TENGs can operate robustly without surface
damage, but their output is considerably lower than that of solid types. To enhance this output, researchers have developed liquid TENGs where the liquid is in direct contact with the conductive material, producing several-mA current. However, the liquid reservoir must be of adequate size for the liquid to move freely, and hence generate electricity. To ensure a compact and lightweight design, we developed a
mobile stick-type water-based TENG (MSW-TENG), which can generate an open-circuit voltage and closed-circuit current to 710V and 2.9mA, respectively.
Powering LEDs with movement
By a research team at Chung-ang University in the Republic of Korea, in cooperation with South Korea and US researchers, with Professor Sangmin Lee as team lead
W
ith the rise of IoT applications and devices, there’s growing demand for portable energy sources to power them. Energy harvesting is a very popular method – from solar power, thermal energy and
mechanical friction, among many other sources. Triboelectric nanogenerators (TENGs) harness mechanical
motion, but they are prone to surface damage from friction. To avoid such damage, triboelectric materials and liquids are used.
38 April 2022
www.electronicsworld.co.uk
MSW-TENG In our lightweight MSW-TENG, a high electrical output can be generated through charge separation and accumulation induced by the water’s self-ionization. To determine the best design, we performed quantitative analyses
with varying ratios of electrode size to the spacing between the electrodes and amount of water. Te proposed TENG can power 100 LEDs, simply by shaking it. Tis can then be used as a self-powered safety device, lighting stick, or something else. In the experiments we used 1-inch perfluoroalkoxyalkane (PFA)
hose and deionized (DI) water, with a 12.5cm stick; see Figures 1 and 4. We used aluminium tape as the inner electrode, with diameters of 5, 11, 16, 20 and 22.5cm (Figure 3c), and the outer electrode placed 2, 4, 6 and 8cm away from it. Te stick contained 5, 10, 15, 20, 30 and 40mL of deionized water (Figure 3b).
Measurements Voltage and current measurements were obtained with a mixed- domain oscilloscope, the MDO 3014 from Tektronix, and a low- noise current preamplifier, SR570 from Stanford Research Systems. For mechanical vibration we used a GBM-02JSK11 motor from the South Korean firm GR Electronics, and a S9KC10BH gear- head from the South Korean firm SPG, with vibration amplitude of 26cm. Te frequency of the shaker was adjusted between 1Hz (60rpm) and 1.5Hz (90rpm). Figure 1a shows that the MSW-TENG consists of a PFA cylinder
which serves as both the substrate and triboelectric material, with the inner electrode at top and bottom of the cylinder, and the outer electrode comprising two bands around its length. A certain amount of DI water is in the tube to ensure consistent contact and separation when shaken. Te inner electrodes seal both ends of the tube; two outer electrodes are bands around the sides. Each generator includes an internal and external electrode and
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