Scientists have come up with a new way to introduce odors into virtual reality via small, wireless interfaces. 

Creating smells in virtual reality is a vexing problem that has prevented consumer VR devices from offering a full sensory experience in most settings. “People can touch in VR,” says Xinge Yu, a professor at the department of biomedical engineering at the City University of Hong Kong and the lead author of the new paper, published today in Nature Communications. “And of course, you can see and hear in VR. But how about smell and taste?”

Previous efforts to create odors in VR have involved multiple wires, messy liquids, and bulky contraptions that don’t lend themselves to home use. 

To tackle the problem, Yu and his co-author, Yuhang Li of Beihang University in Beijing (both of whom have backgrounds designing flexible electronics), developed two wearable interfaces. One can adhere to the skin between the nose and mouth like a bandage; the other straps on beneath a headset like a face mask.

Both types of interfaces use miniaturized odor generators, a grid of tiny containers filled with perfumed paraffin wax. When a heat source beneath the wax is activated, the wax heats up, essentially becoming a scented candle capable of reproducing multiple odors within 1.44 seconds, according to Yu and Li. When the experience is over, a copper coil kicks a magnet to tamp down on the wax and cool down, ending the scent.

The higher the heat, the stronger the odor and the more easily identifiable the smell, Yu says. That means that interfaces can get very hot—up to 60° C (140° F), which is dangerous for human skin. But Yu says the interface is safe because of an “open” design that lets hot air escape, along with a piece of silicone that forms a barrier between the skin and the actual device.

In a test with 11 volunteers, the interface that goes between nose and mouth was judged safe so long as it was at least 1.5 millimeters from the nose, with a temperature at the skin’s surface of 32.2° C, or 90° F—less than human body temperature. Yu realizes, though, that a scalding hot interface attached to your face might not feel safe enough to use, and he said he and Li were testing ways to make the interface run at lower temperatures or cool down more efficiently.

Yu and Li are not alone in trying to create seamless olfactory experiences in VR. At this year's CES, OVR Technology announced that it would release a headset containing a cartridge with eight “primary” aromas designed to mix and match. 

“This is quite an exciting development,” says Jas Brooks, a PhD candidate at the University of Chicago’s Human-Computer Integration Lab who has studied chemical interfaces and smell. “It’s tackling a core problem with smell in VR: How do we miniaturize this, make it not messy, and not use liquid?”

Artists have long attempted to bring scents into entertainment. In 1960, “Smell-O-Vision” made its first and only appearance with the film Scent of Mystery, which released odors during key plot points via air conditioning. But the effort bombed: during screenings, scents were either delayed or too faint to notice. 

These new interfaces are a notable development that could change how we experience VR. Olfaction is a powerful sense and a prerequisite for our mouths to detect flavor. The possibilities range from the obvious—sniffing a virtual flower field or inhaling VR food—to some less obvious applications. For example, perfumeries could test fragrances virtually.

Medically, scent-equipped VR could be helpful for people who have anosmia, or an inability to smell, according to Yu. Scents can also be therapeutic for patients with memory issues and might even help with mood. Yu told me he noticed he felt happier when he used the green tea scent in his tests. He realized that the smell was nostalgic: “When I was little, I’d have some chocolate with a green tea flavor,” he recalled. “I still remember peeling off the wrapper, and how I loved the smell.” 

What stands out about these new interfaces is that they are light, small, and wireless. While the device wasn’t tested directly with a VR game, platform, or specific device, the fact that it can be used without clunky wires should mean fewer tangles, less bulk, and a more immersive experience.

One drawback is that the interfaces remain limited in scope. Yu used 30 different scents chosen for their distinctive, recognizable odors, like rosemary and durian. But many real-life scents are less memorable and might not be as recognizable. Additionally, the miniaturized odor generators have yet to be programmed to work smoothly with existing VR headsets. “It’s hard to say how this would work in a commercial interface,” Brooks says.

Yu says next steps include testing mechanisms to release scents at the right moment. He also wants to start incorporating what he’s learned about smell into figuring out how to introduce taste in VR. Perhaps one day he can replicate the experience of biting into a green- tea-flavored chocolate candy.