Tiny Lens Uses Oil and Water for Focus

March 23 -- Oil and water may not mix. But researchers say the two incompatible liquids can unite to create a unique artificial lens that mimics the workings of the human eye.

Such a lens was introduced recently by Royal Philips Electronics of the Netherlands. Like many common camera lenses, the so-called FluidFocus lens is "variable-focus" — able to bring either near or distant objects into razor-sharp clarity through simple manipulation.

But unlike traditional lenses, the Philips prototype doesn't require moving mechanical parts or a lot of power. That could makes it an ideal optical solution for next-generation digital cameras or other optical devices.

The mechanics of the lens is based on an interesting phenomenon that occurs with water, explain scientists Stein Kuiper and Benno Hendricks at Philips.

"If you put water on a greasy surface, it will take a spherical shape. And if you put it on clean surface, it spreads out," says Kuiper, the senior research scientist on the Philips FluidFocus project.

In other words, the surface of the liquids formed concave or convex curves similar to shape of lenses used in cameras and eyeglasses. And both Kuiper and Hendricks figured out an innovative way to control the shape — and thus the focal power — of their liquid lens.

The FluidFocus lens consists of a tiny sealed glass tube filled with two non-mixing fluids — a non-electrically conducting oil and an electrically conducting solution of water and soap. The interior walls and one end of the tube are coated with clear Teflon-like coating that actually repels water, causing the soapy water solution to form into a hemisphere shape at one end of the tube.

When an electrical charge is applied to the walls of the tube, the water becomes attracted to the sides of the cylinder and the oil flattens the center of solution's hemisphere. Increase the voltage even more, and the water "climbs" up the sides of the tube's walls, forming a convex shape.