For many years, the field of virtual reality (VR) technology has struggled to fully incorporate all human senses into the virtual environment. In addition to sight and hearing, a user wearing VR goggles would need to perceive objects with touch, smell, and taste to achieve a more realistic experience.
To address the challenges surrounding olfaction in the virtual world, a team of scientists from Hong Kong has developed a device resembling a lollipop, capable of recreating several popular flavors within virtual reality. Their research findings have been published in the Proceedings of the National Academy of Sciences (PNAS).
A participant in the experiment is selecting a flavor in the virtual environment, holding a “lollipop” – (Video: Yiming Liu/PNAS).
It is well-known that human taste includes five basic flavors: sweet, salty, sour, bitter, and umami (a Japanese term roughly translated as “savory”). These flavors are stimulated by chemical reactions on the tongue and, to a lesser extent, in other parts such as the throat, larynx, and epiglottis.
Reproducing these sensations in a virtual environment is not straightforward. So far, science has employed mechanisms such as chemical stimuli, temperature, electricity, and iontophoresis.
Creating virtual taste through chemical methods usually involves applying flavoring chemicals directly onto the tongue, but this requires separate chemical containers, and the high latency makes it unsuitable for practical virtual reality applications. Temperature changes can also stimulate taste, but this necessitates a complex system that includes cooling devices and temperature sensors.
Scientists created a “virtual lollipop” – (Illustrative image).
The most common method is electrical stimulation, which simulates the five basic tastes through frequency, intensity, and direction of electrical signals. However, this method requires electrodes to be placed close to the tongue, which can be inconvenient and may even lead to taste biases.
To avoid discrepancies in taste reproduction, researcher Yiming Liu from the University of Hong Kong and colleagues opted for iontophoresis; by moving ions through hydrogels to deliver flavoring chemicals to the tongue, their taste tests achieved the desired stability.
This method is safe, consumes low energy, provides accurate taste feedback, and creates a more natural interface between humans and machines. Liu and the research team enhanced this method by developing a handheld device shaped like a lollipop, improving the quality and consistency of flavors.
Details of the Virtual Lollipop
To create a practical testing device, the team optimally arranged components on two layers of ultra-thin printed circuit boards housed in a lightweight 3D-printed nylon casing shaped like a lollipop. The device features nine flavor-generating channels, loaded with flavor hydrogels made from agarose mixed with mineral water and flavor essences, including sugar, salt, citric acid, cherry, milk, green tea, passion fruit, durian, and grapefruit.
The system components consist of a lithium-ion battery, microcontroller, Bluetooth module, resistors, capacitors, MOSFETs, and a linear regulator that allows control of the taste channels through a graphical user interface (GUI) in the virtual environment.
The final device measures 8×3×1 cm and weighs around 15 grams, comparable to a lollipop.
Virtual lollipop testing.
Flavors are generated through an electric current passing through the gel, releasing flavoring chemicals onto the lollipop’s surface. Users can lick the device to experience the taste, with an accompanying aroma to enhance the sensory experience. Currently, the device’s operational time is limited to about one hour due to the hydrogel shrinking and losing flavor.
Liu and colleagues propose potential applications for this device:
First, a taste testing application conducted in a virtual reality environment. It can help assess taste disorders more objectively and quickly than the current testing process, which requires considerable time and effort to arrange.
The next application is online shopping in a virtual supermarket, where users can sample virtual food.
Finally, the device could be useful in mixed reality educational environments, where parents assist children in exploring different flavors.
