One problem with AR/VR goggles is that they don't make the wearer look adequately silly.

Another issue is that they cannot produce odors. This new invention, meant to be "directly mounted on the upper human lip" using adhesive could solve both issues:

I should admit that this device, developed by researchers at the City University of Hong Kong (CityU), is actually an impressive accomplishment. While smell-producing devices for VR do exist, they're limited to "big instruments to generate odours in a closed area or room, or an in-built bulky VR set," says Dr. Yu Xinge, Associate Professor in the Department of Biomedical Engineering at CityU. That Dr. Yu and his team shrunk it down to this size is remarkable. And because it sits directly under one's nose, "it can provide an ultra-fast olfaction response."

So each of those little squares are called OGs, for Odor Generators.

Here's how they work:

"[Our odour generator] is based on a subtle heating platform and a mechanical thermal actuator. By heating and melting odorous paraffin wax on OGs to cause phase change, different odours of adjustable concentration are released. To stop the odour, the odour generators can cool down the temperature of the wax by controlling the motion of the thermal actuator."

The research team also developed a second, larger version with a mask form factor. This can fit nine OGs into it:

Using different paraffin waxes, the researchers were able to develop 30 different scents, "from herbal rosemary and fruity pineapple to sweet baked pancakes [and] even less-than-pleasant scents, like stinky durian." It's not clear if each OG can produce a single scent or multiple scents.

So what is the application, beyond being able to smell gunpowder while playing Call of Duty? While the demo video shows a person virtually smelling different types of flowers…

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…the researchers do cite a potentially useful medical application: "Helping amnesic patients recall lost memories, as odour perception is modulated by experience, leading to the recall of emotional memories."

Outside of entertainment, I can't immediately think of any applications. Perhaps it might be useful as a form of silent signaling within VR?

Anyway, for the upper-lip version, I do have a suggestion for giving the form factor more visual appeal: