Scientists create a durian-flavored lollipop in virtual reality

For years, the field of virtual reality (VR) technology has struggled to bring all five human senses into a virtual environment. In addition to sight and hearing, a VR user will need to feel objects, smell them, and taste them for the experience to be close to real.

To solve the problems of smell in the virtual world, a group of scientists from Hong Kong developed a device shaped like a lollipop that can reproduce some famous flavors in a virtual reality environment. Their research results were published in the journal Proceedings of the National Academy of Sciences (PNAS).

A test participant selects a flavor in a virtual reality environment, holding a "lollipop" in his hand - (Video: Yiming Liu/PNAS).

We know that human taste consists of five basic tastes: savory, salty, sour, bitter and umami (Japanese for 'meaty'). These flavors are stimulated by chemical reactions on the tongue, and to a lesser extent, in other parts of the body such as the pharynx, larynx and epiglottis.

Reproducing these sensations in a virtual reality environment is not easy. So far, science has used mechanisms such as chemical stimulation, heat, electricity, and iontophoresis.

Chemically inducing taste sensations typically involve dropping flavoring chemicals directly onto the tongue, but this requires separate chemical reservoirs and the high latency makes it unsuitable for VR applications. Temperature variations can also stimulate taste, but require complex systems including refrigeration and temperature sensors.

Scientists create a "virtual lollipop" - (Illustration photo).

The most common method is electrical stimulation , which simulates the five basic tastes through the frequency, intensity, and direction of electrical signals. However, this method requires electrodes to be placed close to the tongue, which is inconvenient and can even lead to taste bias.

To avoid biases in taste reproduction, researcher Yiming Liu from the University of Hong Kong and colleagues chose the iontophoresis method; by moving ions through hydrogels to deliver taste chemicals to the tongue, the taste test achieved the desired stability.

The method is safe, requires little energy, provides accurate taste feedback, and offers a more natural interface between humans and machines. Liu and his team improved on the method by developing a lollipop-shaped handheld device that improves taste quality and consistency.

Virtual lollipop details

To create a streamlined prototype, the team optimally arranged the components on two ultra-thin printed circuit boards, housed in a 3D-printed, lightweight nylon case shaped like a lollipop. The device has nine flavor channels, loaded with a flavor hydrogel 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 include a lithium-ion battery, microcontroller, Bluetooth module, resistors, capacitors, MOSFETs, and linear regulators that allow control of the taste channels via a graphical user interface (GUI) in a virtual environment.

The final device measures 8×3×1 cm and weighs about 15 grams, about the size of a lollipop.

Virtual lollipop test.

The flavor is created by running an electric current through the gel, releasing flavoring chemicals onto the surface of the lollipop. Users can lick the device to taste it, with the added scent enhancing the taste experience. Currently, the device's operating time is limited to about an hour as the hydrogel shrinks and loses flavor.

Liu and colleagues suggest the following potential applications for this device:

First , a taste test performed in a virtual reality environment could help assess taste disorders more objectively and quickly than the current testing process, which is time-consuming and laborious to arrange.

The next application is online shopping in a virtual supermarket where users can taste virtual food.

Finally , the device could be useful in mixed reality (MR) educational environments, where parents help their children explore different flavors.