A transparent electrowetting-on-dielectric device driven by triboelectric nanogenerator for extremely fast anti-fogging

Fogging widely occurs in industrial processes, surgical treatment, and human daily lives. Due to the reduction in transmittance, fogging induces adverse effects or even disaster. Traditional anti-fogging methods face the limitations of large energy consumption and sensitive to contamination. This paper proposes a method of using rotating freestanding triboelectric nanogenerator (RF-TENG) which is capable of converting arbitrary mechanical energy into electricity to drive an electrowetting-on-dielectric (EWOD) device to achieve anti-fogging. The RF-TENG could generate variable open-circuit voltage (0.73–5.26 kV) and frequency (20–100 Hz) by changing the contact area and the rotating speed of the input mechanical energy. The fog droplets coalescence and shedding processes were captured by a high-speed camera, revealing that the droplet oscillation and lateral movement on the EWOD device mainly contribute to the anti-fogging phenomenon. The effects of open-circuit voltage and frequency of the RF-TENG on anti-fogging performance are discussed. The experimental results show that when the open-circuit voltage is greater than ± 1 kV and a frequency larger than 60 Hz is able to achieve a large dry area fraction from 34% to 98% in a very short time (< 0.5 s). Finally, a practical application of using a RF-TENG for window glass anti-fogging was achieved. The results indicate that the EWOD glass show a good visible light transmittance, only 3% lower than the ordinary glass. This study paves a way for utilizing the renewable mechanical energy (e.g. wind) for indoor anti-fogging.