Virtual Reality is not just about 3D vision and sound, it is about simulating all human senses. This is one reason why haptics are so important and interesting, as well as wind systems, treadmills and other whole body interfaces. (See Sensei Alan Craig  for extensive discussion of the theory and practice.)
One of the most difficult senses to “virtualize” has been smell and taste. These chemical senses are intimate and “slow moving”—you have to stimulate receptors on the tongue, and the “signal” operates at the speed of molecular transport (rather than the speed of light). Also, classically, the signals are triggered by a vast array of specific molecules, which is a messy and unintuitive “alphabet”.
My ignorance of this topic was revealed by an amazing paper from Nimesha Ranasinghe and Ellen Yi-Luen Do of National University of Singapore, describing their “Virtual Sweet” system. This device uses thermal stimulation to the tongue to induce the sensation of “sweetness” .
The system builds on research that has shown that themal stimulation (heating and cooling) areas of the tongue can trigger the electro chemical response of taste buds, producing various taste sensations.
The researchers created a precisely controlled array of heating / cooling elements that can be programmed to generate the required patterns. In this case, they generate sensations of sweetness.
As the researchers point out, this might be used to satisfy desires for sweet tasting food, without consuming as much sugar.
It could also be used, as I have implied, to add “flavor” to a VR experience. Now you can taste that imaginary soda drink!
This technology is a bit iffy at this point. Accessing the tongue is awkward (though soft bots and nanotech would be a lot less obtrusive), and there is considerable “slop” in the location of the areas to stimulate.
The researchers note individual differences, and I would expect that there will be considerable variabilty in broader populations, and also depending on experience and environment (just how much sweet food the subjects regularly eat).
Still, this is pretty cool to make it work even partly.
- Nimesha Ranasinghe and Ellen Yi-Luen Do, Virtual Sweet: Simulating Sweet Sensation Using Thermal Stimulation on the Tip of the Tongue, in Proceedings of the 29th Annual Symposium on User Interface Software and Technology. 2016, ACM: Tokyo, Japan. p. 127-128. http://dl.acm.org/citation.cfm?id=2985729
- William R. Sherman and Alan B. Craig, Understanding Virtual Reality: Interface Application and Design, San Francisco, Morgan Kaufmann, 2003. http://store.elsevier.com/Understanding-Virtual-Reality/William-R_-Sherman/isbn-9780080520094/