Muscle-zapper forces gamers' own hands against them

TALK about a hands-on gaming experience. A device for smartphones that sends jolts from a game right into the muscles in your hands has been created to give you a real white-knuckle feel for the action on your screen.

Instead of using motors that drive the vibrating "rumblers" inside phones and game-console controllers, the new system uses two small wired electrodes attached to your forearm to electrically stimulate nerves, making your hand muscles contract.

Developed by Pedro Lopes and colleagues at the Hasso Plattner Institute in Potsdam, Germany, the feedback system uses electrical muscle stimulation (EMS) to mimic the signals that the central nervous system sends to activate muscle groups. Such technology is often used to rehabilitate the muscles of people with varying degrees of paralysis.

The new system creates a strong, painless contraction - in your palm flexor muscle, say - that makes you tilt the phone. "The user then fights that contraction using another muscle to oppose it, so they feel they are fighting a force," Lopes says.

In tests, 10 people played a specially designed video game - in which aircraft had to fight against a strong wind from a giant wind turbine - and compared the new technique with the smartphone's conventional rumbler. "All of them preferred our mobile force-feedback over traditional vibrotactile feedback," Lopes claims.

Because the system has no motors, the researchers say the prototype will be easy to miniaturise and build into a simple add-on for a smartphone, tablet or portable console. And it uses far less power than traditional vibrating motors, he says, so it will not drain a device's battery as quickly.

Chris Harrison of Carnegie Mellon University in Pittsburgh, Pennsylvania, has developed haptic touchscreens for tablets and phones. He notes that beyond medicine and muscle training, EMS has been mainly brought to the fore by artists like Daito Manabe of Japan, who used it to set his facial muscles twitching alarmingly to music.

"As far as we know we're the first to apply EMS to force-feedback in mobile gaming," says Lopes. The system will be demonstrated at the Conference on Human Factors in Computing Systems in Paris, in April.