Sensors smaller than the width of a human hair could prove 1,000 more sensitive than standard DNA tests.
A pinprick of blood might be enough in future
The US scientists behind them suggest they could allow a host of tests to be carried out at a doctor's surgery from one sample of blood.
They suggest that their sensor is the first example of electrical detection of DNA using nanotechnology.
The advance, detailed in the journal Nano Letters, could send instant results back to a handheld organiser.
The research was carried out at Harvard University, and preliminary research focused on its ability to spot genes responsible for cystic fibrosis.
The research team suggest that a practical sensor for the doctor's surgery could be five years away.
At the moment the experiment consists of a business card sized device with a single nanowire.
Nucleic acids - the building blocks of DNA strands in the cell - are grafted onto the wire.
These are designed to pick out only the specific mutation in the DNA of the sample linked to cystic fibrosis.
The wires were then exposed both to normal non-CF gene fragments, and some including the mutation.
The wire could successfully tell the difference between the two types.
Each genetic trait tested for would require a differently loaded nanowire, but scientists believe that the method offers a viable alternative to traditional gene testing, which is time consuming and expensive.
The device could also look out for distinctive gene fragments from viruses.
Professor Charles Lieber, who led the project, said: "This tiny sensor could represent a new future for medical diagnostics.
"What one could imagine is to go into your doctor's office, give a drop of blood from a pin prick on your finger, and within minutes, find out whether you have a particular virus, a genetic disease, or your risk for different diseases or drug interactions."
Even tears, urine and saliva could possibly be tested instead of blood.