Inherent amplitude demodulation of an AC-EWOD (electrowetting on dielectric) droplet

Recently, it has been shown that amplitude modulation (AM) in a wireless EWOD (electrowetting on dielectric) via magnetic induction facilitates the transmission of a low frequency message signal and then the oscillation of droplets at a low frequency. This process requires demodulation to recover the message signal from the high-frequency AM signal. As a key contribution, this paper theoretically and experimentally shows that the EWOD-actuated droplet has the inherent functionality of demodulation. That is, the EWOD droplet itself demodulates a supplied AM driving voltage, and as a result the contact angle of the droplet directly follows the message signal without any artificial demodulation circuit. A theoretical explanation of this inherent demodulation property is developed using a time-varying Lippmann-Young (LY) equation. In addition, experimental results are presented to substantiate the inherent demodulation functionality of an EWOD droplet.