A novel contact lens with a built-in pressure sensor that could help monitor conditions such as glaucoma has been developed by researchers at the University of California, Davis, US.

The device is based on a new technique, which can embed conducting circuits in the organic polymer traditionally used to make contact lenses.

Polydimethylsiloxane (PDMS) is an elastic, transparent and gas-permeable organic polymer that can be cast-moulded into a range simple shapes.

It is widely used in everything from contact lenses to breast implants but the process of cast moulding severely limits the kinds of structures that can be made with the material.

Now, Hailin Cong and Tingrui Pan from the university have come up with a simple method to produce PDMS components without the need for casting moulds and their process can also make the material conduct electricity.

Researchers added a chemical to a liquid PDMS solution that causes the mixture to set, or polymerise, when zapped with UV light.

Then, they exposed the mixture to UV light through a mask containing a circuit pattern.

Only the areas hit by the light polymerise and any remaining liquid can be washed away, leaving an imprint of the circuit.

The technique can be used to create features just 10 micrometers in size.

Researchers have also developed a technique to give the polymer another property - electrical conductivity.

They did this by adding a solution of silver to the mix. The silver then becomes trapped in the material when it polymerises, creating a path along which electrons can pass.