Wireless driven EWOD technology for a MEMS pond skater

Abstract

A silicon swimming robot or pond skating device has been demonstrated. It floats on liquid surfaces using surface tension and is capable of movement using electrowetting on dielectric (EWOD) based propulsion. Its dimensions are 6×9mm with a thickness of 380μm. The driving mechanism involves the trapping of air bubbles within the liquid onto the hydrophobic surface of the device with the subsequent ejection using a recently reported Ta <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> O <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</inf> EWOD technology. The required driving voltage of ∼15V is low enough for RF power transmission, thus providing wire-free movement. A wired version has been measured to move 1.35mm in 168ms (a speed of 8 mm s <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−1</sup> ). This low-voltage EWOD device, fabricated using a CMOS compatible process, is believed to be the world’s smallest swimming MEMS device that has no mechanical moving parts. The paper also reports results of EWOD droplet operation driven by wireless power transmission and demonstrates that such a wireless design can be successfully mounted on a floating EWOD device.