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A user wearing haptic devices on two fingers feels both real and virtual objects in augmented reality. 

Domenico Prattichizzo

Finger devices let users ‘touch’ virtual objects

Less than a year ago, augmented reality—digital effects laid on top of the real world as seen through a computer screen—burst into public consciousness with the release of the mobile game Pokémon GO, in which players see magical little monsters in the real world using their smartphones. Now, a team of engineers has done them one better: With finger-worn devices, users can “feel” virtual objects around them while still maintaining the ability to grasp other—actual—objects. The new technology could upgrade everything from video games to ecommerce to neurosurgery.

More than 100 million people have experienced augmented reality through Pokémon GO, and tech giants including Apple, Microsoft, Google, and Facebook are investing in it. But so far, augmented reality and its sibling, the fully immersive virtual reality, have an obvious limitation: You can see and hear virtual objects, but you can’t touch or feel them. 

Over the years, engineers have constructed gloves with motors or electrodes designed to provide tactile, or “haptic,” feedback. But because most cover the fingertips, users have to remove them before they can feel a real object. Devices that leave the fingertips free don’t give the fingers much feedback, or consist of ungainly exoskeletons on the backs of the hands.

So Domenico Prattichizzo, a robotics engineer at the University of Siena in Italy, and his collaborators designed two devices that enable users to feel virtual objects, which they put to the test in a paper to be published in IEEE Transactions on Haptics. One fits over the fingertip, like a chunky thimble. It has a thin plate controlled by three tiny motors that presses against the finger pad. The plate is thin enough to let users pick up real objects, but substantial enough to make them think they are touching real objects—even when none is there. The other is a ring worn high on the finger that uses tiny motors to stretch the skin under the ring. When the stretching, inches from the fingertip, combines with visual feedback, the brain essentially fools itself and transfers the sensation to the tip.

Participants tested the devices with three tasks. In the first, they held a real piece of chalk and wrote the word “CIAO” (goodbye) on a virtual whiteboard, which they saw through a computer screen. When the chalk touched the virtual board, it left a mark, which turned from blue to red as the subject pressed harder. Participants wore thimbles, rings, or nothing on the thumb and index finger. Compared with bare fingers, the haptic devices each reduced people’s tracing error by about 75%. Participants also reported the thimble and ring gave them better control of the chalk. In additional trials, the only device to do better was a stylus controlled by mechanical arms that can’t be worn.

In the second task, people placed two virtual blocks on top of two real blocks, which they then picked up and moved. Participants were about 30% faster with the haptic devices than without. In the third task, they held a real square of cardboard and rolled a virtual ball on it toward several targets. Participants hit more targets in 45 second with haptic feedback—which simulated the weight of the ball rolling on the cardboard—than without it. In this final task, the thimble was slightly better than the ring.    

Prattichizzo’s lab has led “a revolution in the topic of virtual touch,” says Miguel Otaduy, a computer scientist at Rey Juan Carlos University in Madrid. He’s tried Prattichizzo’s devices and is impressed that you can wear them and still hold real objects. “That just blows your mind,” he says. Samuel Schorr, a mechanical engineer at Stanford University in Palo Alto, California, who studies haptics in virtual reality, praises the work for comparing different types of devices using different types of tasks.

Otaduy notes several possible applications. In medicine, a surgeon might be able to perform remote operations beyond the simple use of a scalpel, or train for tumor screening by feeling for virtual lumps in real tissue. In telecommunications, people could share touch over the internet. Sensing could also be remote in time: You might record the visual, audio, and tactile sensations of playing with your child, for example, to play back later.

Prattichizzo hopes to add vibrations to his wearable devices to simulate texture. He’s also developing armbands to provide haptic feedback when lifting heavy virtual objects. Some of these ideas may soon come to market through his new company, WEART: “My goal is that we should be able to switch from real to virtual reality in a snap.”