SkinTrack Turns Your Arm Into A Smartwatch Touchpad
A new wearable technology transforms your whole lower arm into a touchpad, widening smartwatch interactions beyond the small watch face.
Called SkinTrack, the system allows for continuous touch tracking on the hands and arms. It also can detect touches at specific locations on the skin, creating functionality similar to buttons or slider controls.
“The great thing about SkinTrack is that it’s not obtrusive; watches and rings are items that people already wear every day,”
Existing “skin to screen” approaches have used interactive textiles, flexible overlays, and projector/camera combinations that can be cumbersome. SkinTrack demands only that the user wear a special ring, which producess a low-energy, high-frequency signal through the skin when the finger touches or nears the skin surface.
“A major problem with smartwatches and other digital jewelry is that their screens are so tiny,” says Gierad Laput, a PhD student at the HCII. “Not only is the interaction area small, but your finger actually blocks much of the screen when you’re using it. Input tends to be pretty basic, confined to a few buttons or some directional swipes.”
“SkinTrack makes it possible to move interactions from the screen onto the arm, providing much larger interface.”
Watch Strap Electrodes
By using electrodes integrated into the watch’s strap, it’s possible to pinpoint the source of the electromagnetic waves coming from the ring because the phase of the waves will vary.
For example, electrodes corresponding to the 12 o’clock and 6 o’clock positions on the watch can detect phase differences that can determine the position of the finger along the width of the arm. Electrodes at the 3 o’clock and 9 o’clock positions can determine the finger’s position along the length of the arm.
Researchers found that they could determine when the finger was touching the skin with 99 percent accuracy and they could resolve the location of the touches with a mean error of 7.6 millimeters. That compares favorably with other on-body finger-tracking systems and approaches touchscreen-like accuracy.
Drawings, Maps and Games
The researchers showed that SkinTrack can be used as a game controller, to scroll through lists on the smartwatch, to zoom in and out of onscreen maps, and to draw.
A number pad application lets you use the back of your hand as a dial pad for the onscreen number pad; hovering a finger over the hand acts as a cursor, highlighting numbers on the screen to aid in targeting touch points.
There are a few limitations, though. Keeping the ring powered up has been a challenge.
Signals also tend to change as the device is worn for long periods, thanks to factors such as sweat and hydration and the fact the body is in constant motion.
On the plus side, the technology is safe. No evidence suggests that the radio frequency signals used by SkinTrack have any health effects. The body is commonly excited by daily appliances—everything from the tiny amounts of current drawn from the finger by touchscreens to the electromagnetic noise emanating from fluorescent lights, with no ill effects.