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Modern virtual reality is a feast for the eyes and ears—but coming in a distant fourth (behind haptic touch technologies), smell has been nearly completely ignored.
Earlier this month, Chinese researchers published a paper in Nature Communications that details a small, soft, wireless olfactory device that might finally give your sniffer something to do. The key breakthrough is a “miniaturized odor generator” small enough to slip inside a flexible face mask.
Countless inventors and researchers have tried to popularize “smellovision” in whatever incarnation—whether in its hyphenated Smell-O-Vision cinematic form or in various other olfactory tech offshoots—with little success. The earliest example is an 1868 stage performance in London that reportedly sprayed scents from fragrance giant Rimmel, at the time a local boutique, into the crowd. Modern examples are far more complex. But an effective, affordable solution for delivering smells on demand remains elusive.
The original Smell-O-Vision (and its rival, AromaRama)
Hans E. Laube introduced his Smellovision (later rebranded Smell-O-Vision) at the 1939 New York World’s Fair. His invention used a system of pipes attached to a circular mechanism carrying vials of odorous liquid. A control board was used to release the scents, which wafted to moviegoers through pipes hidden beneath their seats. Laube aimed to bring it to homes: a blurb in the 3 February 1946 issue of the St. Louis Globe-Democrat claimed that “Smellovision will be able to bring more than 2,000 different aromas right into your living room.” That proved optimistic, and Smellovision was rarely mentioned for the remainder of the decade.
Smellovision finally reappeared alongside the 1960 film Scent of Mystery, a thriller that challenged moviegoers to identify its villain through olfactory clues. It faced a less sophisticated competitor, AromaRama, which dumped scents into a theater’s air conditioning. Associated Press reporter Bob Thomas gave the advantage to Smellovision, saying that “the smells are truer and more varied than in .”
Yet the idea never caught on. Price was a likely problem: Smellovision reportedly cost “a quarter of a million” U.S. dollars to install.
Smell the first golden age of VR
Virtual reality had a moment in the 1990s as improved displays and 3D-rendering techniques made head-mounted displays (HMD) viable—and some wanted to add scents to the sights.
BOC Group, a U.K. industrial-gas company, built a device for use with HMDs that delivered odors through a computer-controlled air stream. Ferris Productions, an entertainment company in the United States, built a similar system for its line of virtual reality Experience Systems, which were used at theme parks like Six Flags Fiesta Texas.
The U.S. Air Force Fire Research Group, meanwhile, put VR to practical use with FiVe FiRe Training, a VR firefighter training system with an “odorpak” that mimicked the scent of burning wood, grease, or rubber. A photo shows a bulky system with numerous tubes dangling off the trainee. It wasn’t a problem for firefighter training, perhaps, but too large for easy personal use.
Solenoid valves and atomizers miniaturize the concept
Takamichi Nakamoto kicked off a new approach to smellovision with a 2006 paper published in the proceedings from that year’s IEEE Virtual Reality Conference, “Movie with Scents Generated by Olfactory Display Using Solenoid Valves.” A 2008 followup paired the technique with a video game that let virtual cooks both see and smell their virtual dish. The device used “real-time scent blending” of 32 odor components to create an “olfactory display” that mixed scents for more variation. It was smaller than prior devices, though still larger than a laptop.
The concept was further refined in a 2018 paper in the IEEE Sensors Journal, which described the addition of an acoustic wave (SAW) atomizer. The SAW used ultrasonic waves to vaporize scented liquids, rapidly fabricating mixes that smell identical to manually preblended odors. It also further reduced the size of the device, though still apparently too large for an HMD and instead placed on a table in front of a user.
Tired of waiting for latter-day smellovision? Do it yourself
HapticSol, a Texas startup founded by Peter Sassaman and Abraham Zodick, launched a smellovision development kit on Kickstarter in 2015. The project failed, but development continued. The device was ultimately released in 2020 under the name Cilia.
Cilia is built to be placed on a tripod near a user wearing an HMD and disperses scents from up to six vials. It’s a mechanically simple system, but this cuts the cost: Anyone can purchase Cilia for just US $475. HapticSol builds a smaller version, Micro Cilia, priced at just $275 and designed to be worn like a necklace.
That doesn’t mean it’s for everyone. Cilia offers plug-ins for Unity and Unreal Engine, but only a handful of games support it out of the box. VR enthusiasts hoping to smell what they see must code it themselves.
“The Smell Engine” pairs with the Unity game engine
In April of 2022 researchers from Arizona State University revealed the most alluring smellovision yet: “The Smell Engine.” Its design is similar to Nakamoto’s olfactory display, but scents are directed into a nose mask small enough to use with consumer HMDs such as Meta’s Oculus Quest.
Like Project Cilia, the Smell Engine was designed alongside software compatible with the Unity game engine. A developer can use a “smell composer” to tell the device what a user should smell when near a virtual object. The device can then “dynamically estimate” the odor mix to change the smell, as well as its strength. It’s not perfect, however. While the Smell Engine is shown attached to consumer HMDs, it requires a tube connected to a larger external device which stores the scents and handles mixing.
Olfactory generators are the latest breakthrough
Which brings us back to the recent paper published in Nature Communications. It introduces an “olfactory generator” (OG) that measures roughly 1.5 centimeters across. Each OG can produce a single scent through boiling a scented liquid with a small heating element.
The size of each OG is what sets this method apart. Prior attempts at smellovision struggled with piping smells from large external odor-generating devices into a VR headset. That’s a big problem in VR experiences that allow a user to stand up or walk freely in a space. The paper shows mask designs with two or nine OGs, each of which operate wirelessly.
There are disadvantages to this approach. The paper notes that a “low-volatile odor compound...could continuously release odor for 91 min[utes].” That could force frequent replacement of odor compounds. Still, discarding awkward wires and tubes is a notable advancement that puts our nostrils one step closer to smelling the virtual flowers.
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