Two-axis electrowetting liquid lens for beam steering

Electrowetting controlled liquid lenses have emerged as a useful technique for steering light. In this study, we report on a novel hexagonal cell design of an electrowetting device for two-axis solar tracking. This study proposes an array of these hexagonal electrowetting cell structures to facilitate a planar device that can steer sunlight coming from a range of directions. A proof of concept device is fabricated to demonstrate this design. The hexagonal cell is dosed with two immiscible liquids. The liquid-liquid interface is modulated by varying the voltage to different electrode faces in the cell. By deforming the liquid shape in an electrowetting cell, light can be steered and concentrated for solar energy applications. Here, the study demonstrates that the interface can be tilted vertically by applying a voltage to the side electrode faces. By sequentially applying a voltage to different electrode faces, the interface can be rotated 360° horizontally. Finally, the study demonstrates a 4.5° change of laser beam path with only a 0.2 refractive index difference of the liquids. The device has the potential to eliminate the disadvantages associated with bulky mechanical tracking devices. A thin array of electrowetting cells can be placed on a Fresnel lens and direct the sunlight towards the Fresnel lens for concentration without extra tracking. The electrowetting cell array can also be used to steer and concentrate solar energy onto a concentrated photovoltaic cell directly.