Apart from size, NailO's creators say a key selling point could be discretion. The device is controlled by running a finger over its surface. Touching your thumbnail is a natural activity, so most people wouldn't notice this as a deliberate action to control a device.

In a video demonstrating what will be a new class of wearable device, it is shown being used to scroll through a recipe while the wearer's hands are otherwise occupied holding spoons while preparing food.

MIT Thumbnail Trackpad
The NailO uses the same capacitive technology as smartphone screens and connects via Bluetooth to parent devices. Image: MIT

The processor, battery, sensing chip and Bluetooth radio are included on a circuit board that sits under the capacitive trackpad. The two are connected via a small ribbon cable, which means the trackpad is not quite as thin as a stick-on nail, but reducing the size is one of the aims of the researchers.

Researchers are looking to consolidate the components into a single chip, which will make it smaller and reduce power consumption, said Artem Dementyev, a graduate student in media arts and sciences and one of the developers. And they are already talking to manufacturers in China about a battery that could fit in the space of a thumbnail and is only half a millimeter thick.

Artem Dementyev said that it wasn't easy to pack all the necessary hardware into a device no bigger than an outsized thumbnail.

"The hardest part was probably the antenna design," he said. "You have to put the antenna far enough away from the chips so that it doesn't interfere with them."

Details of the prototype will be presented at next week's Computer Human Interaction conference in Seoul, South Korea.