The mChip is about the size of a credit card and can diagnose infections within minutes, according to a study in the journal Nature Medicine.

Prototype tests for diseases such as HIV and syphilis in Rwanda showed almost 100% accuracy, it said.

The US-developed device has a projected cost of $1 (60p).

This would make it much cheaper than the lab-based tests currently used.

The plastic chip contains 10 detection zones, and can test for multiple diseases with only a pinprick of blood.

Results can be seen with the naked eye or with a low-cost detector.

"The idea is to make a large class of diagnostic tests accessible to patients in any setting in the world, rather than forcing them to go to a clinic to draw blood and then wait days for their results," said Samuel Sia, a professor at New York's Columbia University who is a lead developer of the device.

Hundreds of tests using a prototype of the device were carried out in Kigali, Rwanda. They showed 95% accuracy for HIV and 76% accuracy for syphilis, the study says.

Researchers hope to use the mChip to help increase testing of sexually-transmitted diseases (STDs) in pregnant women, particularly in Africa.

A version of the device has also been designed to test for prostate cancer.