High efficient harvesting of underwater ultrasonic wave energy by triboelectric nanogenerator

Ultrasonic waves are existing in water and in our living environment, but harvesting the sonic wave energy especially in water is rather challenging, simply because of the high pressure generated by water. In this work, a triboelectric nanogenerator (TENG) has been designed using spherical pellets as the media for performing the contact-separation operation during ultrasonic wave excitation for energy harvesting. The fabricated TENG can attain an instantaneous output current from several milliamps to about one hundred milliamps and achieve an output power of 0.362 W/cm2 at an ultrasonic wave frequency of 80 kHz. The average power conversion efficiency of the TENG has reached 13.1%. The equivalent output galvanostatic current is 1.43 mA, which is the highest value reported so far. The developed TENG pellets has been demonstrated to continuously power up to 12 lamps with 0.75 W each, and can continuously drive a temperature-humidity meter, an electronic watch, and directly drive a health monitor. This study presents the outstanding potential of TENG for underwater applications.