Fluid lens flows into focus

By controlling a boundary between oil and water, researchers have created a liquid lens that can quickly alter its shape in response to electric signals.

Able to adjust its focusing distance from 5 centimeters to infinity in less than 10 milliseconds, the miniature lens may provide variable focusing for digital and cellphone cameras, medical endoscopes, and other products, claim Stein Kuiper and his colleagues at Philips Research of Eindhoven in the Netherlands. The company unveiled a crumb-size prototype of its new lens last month at a trade exhibition in Germany.

To make the lens, Philips researchers applied a water-repellent coating to the inside of a tiny tube capped at one end. Adding drops of a watery solution and oil to the tube and then sealing the open end with a transparent, uncoated cap, the researchers found that the water hunkered down into a hemispherical lens at the uncoated end.

By applying a voltage to the tube, the researchers could diminish the coating’s repulsiveness, allowing the lens’ outside edge to creep up the once-repellent walls by capillary action. As the water climbed the walls under various voltages, the curvature of its upper surface changed, modifying the lens’ focal length.