Giving your digital camera a virus may not sound very smart, but a memory chip that incorporates millions of viruses may just be the fastest thing around.

By coating 30-nanometre-long chunks of tobacco mosaic virus with platinum nanoparticles, it’s possible to create a transistor with very fast switching speed. Millions of these transistors could eventually be used in a memory chip to replace flash memory in mp3 players and digital cameras, for example.

A camera fitted with a virus chip would take a few microseconds to display an image, compared with the milliseconds taken by existing devices, says Yang Yang of the University of California, Los Angeles, whose team is working on the virus chip.

The team built a transistor by embedding the coated virus strips in a polymer matrix, sandwiched between two electrodes much like a standard transistor. Apply a voltage to the transistor, and the platinum nanoparticles – roughly 16 per virus – each donate an electron to proteins on the surface of the virus, moving the device to an ON state.

When the voltage dips below a certain threshold, the electrons jump back to the nanoparticle, switching the transistor to an OFF state (Nature Nanotechnology, DOI:10.1038/nnano.2006.55).

This process takes just 100 microseconds because the charge only has to travel 10 nanometres between each nanoparticle and the surface of the virus. In flash memory chips, a capacitor is used as a control gate, building up charge to a certain level before current is able to flow to a second gate.

The device is still some way from practical use in a memory chip. “Now we need to figure out how to wire up the viruses,” says Yang. They hope to build a prototype packed with millions of single-virus transistors within four years.