A cheap test which could detect even low levels of viruses and some cancers has been developed by UK researchers. The colour of a liquid changes to give either a positive or negative result.
The designers from Imperial College London say the device could lead to more widespread testing for HIV and other diseases in parts of the world where other methods are unaffordable.
The prototype, which needs wider testing, is described in the journal Nature Nanotechnology.
The test can be configured to a unique signature of a disease or virus — such as a protein found on the surface of HIV.
If that marker is present it changes the course of a chemical reaction. The final result is blue if the marker is there, red if the marker is not.
The researchers say this allows the results to be detected with "the naked eye". The researchers expect their design will cost 10 times less than current tests. They say this will be important in countries where the only options are unaffordable.