IThat was it one of those many inventions that never really caught on. In 1960, viewers of the film “Scent of Mystery” were able to experience the wonders of “Smell-O-Vision”. Mounted under the cinema seats, the system emitted 30 different scents at key moments in the story – from a salty sea breeze to a hint of wine. The system had its quirks. Those on the balcony complained that the smells reached them too late. Others found the scents too weak or annoyingly persistent. More novel than effective, Smell-O-Vision never really caught on in Hollywood.

Nowadays, video games and virtual reality are no longer movies, but video games and virtual reality. Several groups are trying to bring scents into virtual worlds. In an article published this week in nature communication, Xinge Yu from the City University of Hong Kong and Yuhang Li from Beihang University describe two wearable “Olfaction Interfaces”. The first is the size of a patch and is taped to the skin under the user’s nose like a fake mustache. The second, more powerful variant is a flexible face mask.

Both are based on heating tiny flakes of paraffin wax that have been impregnated with various liquid perfumes. The smaller version of the system uses two such tiles; the larger has nine. Researchers claim they can create a scent like mint or green tea in just 1.44 seconds. The nine generators on the mask can be combined to create hundreds of possible smells.

Doctors Li and Yu were launched OVR, a startup based in Vermont. His headset uses a system of refillable cartridges, each capable of producing thousands of scents. The company’s latest product, the “ION3″ will be released later this year and can be integrated into existing game creation tools with minimal effort.

The right smells could make virtual worlds more attractive. Smells are known to be evocative. The part of the brain that processes them is directly connected to parts associated with emotions and memories. But the science is tricky. Unlike colors or tones, which combine wavelengths and frequencies in predictable ways, smell isn’t that simple. Changing a single chemical bond can turn a scent from sweet to rancid. Whether smelly VR will do better than smelly films remains to be seen. But maybe one day users will be able to stop, swipe and smell the virtual roses. ■

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