In order for a VR environment to seem real, it definitely helps if you can experience the sensation of touch within that virtual world. A special sleeve could soon allow people to better do so, using air instead of electric motors.
In most haptic feedback systems we've seen so far, the sensation of being touched is managed via arrays of small motor-type actuators which vibrate against the skin. Depending on the intensity, duration and sequence of those vibrations, sensations such as being tapped, stroked or squeezed can be simulated.
One alternative involves replacing the motors with lighter, less complex and more energy-efficient inflatable elastomer pouches. These pneumatic actuators simulate touch by selectively inflating and expanding, pressing down against the skin as they do so.
In order to press downwards sufficiently, the actuators have to be kept from expanding in other directions as they're inflated. As a result, such systems are often incorporated into relatively bulky exoskeletons with rigid sections that direct the expansion of the pouches.
That's where the Haptiknit system comes in. It's being developed by a Stanford University team led by Prof. Allison Okamura, working with colleagues from MIT.
The setup is currently being demonstrated in the form of a prototype sleeve which incorporates a total of eight pneumatic actuators arranged in two rows of four. Each pouch can be individually inflated and deflated via a thin hose running to an arm-worn battery-powered pump.
The main body of the sleeve was made by knitting nylon and cotton fibers. Thermoplastic fibers, however, were additionally used in the circular dish-shaped sections which house the actuators.
By applying heat to those areas once the knitting process was complete, the scientists caused the thermoplastic fibers to melt and then stiffen upon cooling. Those areas then formed rigid housings for the actuators, which directed their expansion down towards the wearer's skin.
"A challenge in the field of soft robotics is how do you stick together something hard and something soft – they tend to delaminate," says Okamura. "But putting these fibers into knitting makes a totally seamless transition from parts that are hard to parts that are soft, because it’s one continuous fabric."
In an assessment of the technology, both the Haptiknit sleeve and a similar array of eight motorized actuators were tested on 32 volunteers. It was found that with the Haptiknit system, the test subjects were better able to determine the locations of individual virtual taps on their arm.
The sleeve was also successfully used to deliver a virtual stroking sensation, by sequentially activating the pouches one after another. What's more, because the participants described the device as being comfortable and easy to use, the technology could ultimately find use in applications beyond VR.
"Whether the purpose is entertainment, communication, training, or physical assistance, this really brings these wearable devices toward things that people might actually want to use in their everyday lives," says Okamura.
The research is described in a paper that was recently published in the journal Science Robotics. You can see the sleeve in arm-pressing action, in the video below.
Source: Stanford University
