inside science & technology

February 2008

Exploring Virtual Worlds Through the Sense of Touch

By Grace V. Jean

Millions of receptors and sensory cells lie beneath the skin to help us discern the physical world that we live in. Of our five senses, only the sense of touch extends throughout our bodies and allows us to detect the temperature, pressure, movement and texture of objects in our surroundings. Is it any wonder then that digital gizmos are catering more and more to this essential sensor?

Chances are you already own a gadget that incorporates some form of haptics, or tactile feedback technology. Pick up your cell phone, or that PlayStation game controller. Both will vibrate to let you know that you’re missing a call or that you’re going out of bounds in a video game.

The iPhone and the Nintendo Wii have taken the technology another step further. Now we can swipe our fingers across a glossy surface to expand or contract web browsing screens or cast virtual fishing lines and feel the fish nibbling at the bait.

Some cell phone manufacturers have followed Apple’s lead by eliminating their keypads and substituting touch screens as the primary user interface. These devices incorporate vibration-feedback to let users know they have “pressed” a button.

Until recent years, technologies employing haptics were found mostly in niche applications, such as the automotive and aerospace industries where computer simulations help engineers design vehicles and aircraft. But the concept of tactile feedback has gained so much popularity that it’s becoming pervasive in numerous areas.

In the medical realm, computer simulations increasingly are being embraced as useful training tools for surgeons. Researchers are beginning to fuse haptics into these virtual trainers. Using hands-on tools that simulate the appropriate levels of resistance, doctors can “operate” on patients and receive realistic tactile feedback.

One such trainer can be found at Walter Reed Army Medical Center, Md., where scientists at the National Capital Area Medical Simulation Center are developing a computer-based simulator to help medics learn how to do a cricothyroidotomy, or surgical airway in the throat. The simulation blends haptics and stereographic technologies to create a realistic experience for medics.

Trainees wear special glasses to see the patient on the computer screen pop out in 3D. Grasping two stylus “pens” that are mechanically connected to motors, trainees can “touch” the patient and feel the bumps and ridges of his throat. When making the incision, the medics must use sufficient force to break into the skin and they can feel resistance as their scalpels make the cut.

Once the airway has been created, trainees must learn how to insert a breathing tube. It proves to be a challenge, both for the user as well as the scientists behind the simulation.

“This is the only part that we can’t simulate perfectly,” said Alan Liu, director of virtual medical environments at the center. It’s difficult to maneuver the tube using the stylus, in part because its mechanical linkages limit freedom of movement. Preliminary research in magnetic levitation haptics promises to liberate the stylus from those linkages and motors and still provide the same force feedback, said Liu.

The simulation has been field-tested by surgical teams and medics at Balad Air Base in Iraq. Liu said the researchers have received positive feedback from those troops and that the team is working on improvements to give the trainer more realism.

There are other applications of haptics for war fighting. Troops who are being overloaded with devices that give visual and aural cues may find the idea of tactile cues to be appealing.

“Fire team members say, ‘don’t obstruct my vision or hearing because I’m looking for baddies,’” said Jack Vice, president of AnthroTronix, a Silver Spring, Md.-based company that is developing haptics-based technologies to provide warriors with information through their touch receptors.

One such technology is a belt that vibrates in different ways to notify troops when a bomb disposal robot has arrived on the scene.

Vice said that researchers are working with another company to develop a haptic language in vibrations. It would be similar to Morse code, but instead of dots and dashes, the language would have variations in intensity, frequency and location.

“You could have a full word or message and develop a lexicon for that,” said Vice.

In conjunction with the language, the company plans to develop its belt into a vest, which would expand its options for relaying a variety of tactile communications.

Despite all the research, some skeptics believe that haptics is still a niche application in an ever expanding world of simulations.

“Haptics is the future, but there’s a long way to go,” said Gabe Batstone, vice president of business development and sales at Ngrain, a Canadian simulation company.

Please email your comments to GJean@ndia.org

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