Philips is getting a lot of attention for having invented a new kind of lens that might be used in cell phones and other small electronics that currently don’t offer lenses with the ability to focus. This is done by using two liquids that don’t mix, and applying a small electrical charge to change the shape of the lens. Or, more technically:
The Philips FluidFocus lens consists of two immiscible (non-mixing) fluids of different refractive index (optical properties), one an electrically conducting aqueous solution and the other an electrically non-conducting oil, contained in a short tube with transparent end caps. …
The shape of the lens is adjusted by applying an electric field across the hydrophobic coating…
But what is really interesting is that the idea, or at least parts of it, is not new. According to my friend, J. Greenberg, an expert on older cameras, this is
an idea from 1859, when Thomas Sutton filled a glass ball with water, mounted it on a piece of metal, and called it the “Sutton Panoramic Lens”. Later reinvented by JG Baker in 1942.
For more info, he recommends the book A History of of the Photographic Lens, by Rudolf Kingslake.
A diagram of Sutton’s lens can be found here.