Switchable liquid shutter operated by electrowetting for security of mobile electronics

Abstract

This paper presents a new type of switchable liquid shutter for the security and design of mobile electronic devices. The operation test of the liquid shutter is conducted using a prototype sample prepared by standard microfabrication processes. The liquid shutter consists of an opaque liquid for absorbing light and a transparent oil for transmitting light on two parallel plates with patterned indium titanium oxide electrodes. The liquid shutter can be opened and closed by sequentially applying an electrical voltage to the patterned electrodes owing to an electrowetting principle. The switching time of the liquid shutter is measured using a high-speed camera and is found to take about 550 ms to open the shutter and 240 ms to close the shutter at 70 Vrms (1 kHz). To validate the applicability of the liquid shutter, the operation of liquid shutters with different colored liquids mounted on a smartphone is successfully demonstrated. The proposed liquid shutter not only allows a simple design to be easily miniaturized and integrated with electronic devices but also provides a robust and fast switching operation.