This ‘ring’ turns your arm into a touchpad

Scientists have developed a new wearable technology that may be able to turn your entire lower arm into a touchpad for a smartwatch.

Called SkinTrack and developed by researchers from the Carnegie Mellon University in the US, the new system allows for continuous touch tracking on the hands and arms.

It also can detect touches at discrete locations on the skin, enabling functionality similar to buttons or slider controls, researchers said.

Previous "skin to screen" approaches have employed flexible overlays, interactive textiles and projector/camera combinations that can be cumbersome.

SkinTrack, by contrast, requires only that the user wear a special ring, which propagates a low-energy, high-frequency signal through the skin when the finger touches or nears the skin surface, researchers said.

"The great thing about SkinTrack is that it is not obtrusive; watches and rings are items that people already wear every day," said Yang Zhang from Human-Computer Interaction Institute's Future Interfaces Group (HCII).

"A major problem with smartwatches and other digital jewelry is that their screens are so tiny," said Gierad Laput from HCII.

"Not only is the interaction area small, but your finger actually blocks much of the screen when you are using it. Input tends to be pretty basic, confined to a few buttons or some directional swipes," said Laput.

"SkinTrack makes it possible to move interactions from the screen onto the arm, providing much larger interface," said Chris Harrison from HCII.

The user wears a ring that produces a high-frequency electrical signal. When the finger gets near to the skin or touches the skin, that signal propagates through the skin, researchers said.

By using electrodes integrated into the watch's strap, it is possible to pinpoint the source of those electromagnetic waves because the phase of the waves will vary, they said.

Researchers found that they could determine when the finger was touching the skin with 99 per cent accuracy and they could resolve the location of the touches with a mean error of 7.6 millimetres.

That compares well with other on-body finger-tracking systems and approaches touchscreen-like accuracy.

Researchers showed that SkinTrack could be used as a game controller, to scroll through lists on the smartwatch, to zoom in and out of onscreen maps, and to draw.

The technology is safe. No evidence suggests that the radio frequency signals used by SkinTrack have any health effects, they said.