Artificial Tongue Inspired by Mammalian Tongues

Innovation: Academia

Ulsan National Institute of Science and Technology

2020

Image: Tamas Pap / Unsplash / CC BY SA - Creative Commons Attribution + ShareAlike

Send Chemical Signals (Odor, Taste, Etc.)

Tastes, odors, and hormones are all chemical signals that can float through the air or water, or be applied to solid surfaces. Chemicals are important for signaling and communication; even humans, with our underdeveloped sense of smell, are influenced by chemicals more than we realize. Chemical signals are often specific to the living system intended to receive them, and are often relatively weak, dispersing upon moving through liquids or gases. To ensure that chemical signals reach their target, living systems create unique chemical signals and methods of dispersal. One example is an orchid that is pollinated by dung beetles, and therefore distributes a dung-smelling aroma to attract them.

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Sense Chemicals (Odor, Taste, etc.) From the Environment

Chemicals are important for signaling and communication among living systems, either intentionally (such as when two living systems try to find one another) or unintentionally (such as when a plant emits a chemical signal that an herbivore can use to find a tasty bite). They are also important for other uses, such as navigating or finding sources for minerals. But chemical signals are often relatively weak and disperse when moving through water or gases. Therefore, detecting them requires specialized abilities, including a way to determine where they are coming from. A well known example of sensing chemicals can be seen in ants following a pheromone trail laid down by others in their colony to locate a quality and abundant food source.

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Soft artificial tongue from Ulsan National Institute for Science and Technology has a saliva-like chemiresistive ionic hydrogel that is able to taste astringency.

Benefits

Flexible
Increased sensitivity

Applications

Medical Implants
Robotics

UN Sustainable Development Goals Addressed

Goal 3: Good Health & Wellbeing

The Challenge

Artificial tongues have been developed to detect the five basic tastes, including sweet, sour, bitter, salty and umami. However, more complex tastes such as astringency (acidity or bitterness) is more difficult to detect. These artificial tongues have been developed based on lipid/polymer membranes or stripped epithelium cells, giving the tongue reduced selectivity and a narrow detection range.

Innovation Details

The specific molecules that cause the perception of astringency can be found mainly in unripe fruits, wines and teas. The thin layer of saliva on the tongue is important for tasting because it absorbs the molecules and enables them to bind to receptor cells, which send signals to the brain that it is tasting an astringent food. Researchers mimicked this salivary layer by creating a thin hydrogel layer on top of a 3-D porous network that facilitates the flow of electrolytes. The hydrogel absorbs the astringent-causing molecules, causing them to clump together. This enhances the ion-conductivity of the hydrogel, causing an increased current that sends a signal that astringent molecules are present.

Overview of the astringency detectable sensor. Photo: Jeonghee Yeom/Ulsan National Institute of Science and Technology.

Biological Model

Tongue are soft, flexible muscular organs responsible for the sense of taste. The tongue has mechanical receptors and ion channels that assist in the translation of signals used for taste perception. In addition, saliva plays a key role in tasting because it absorbs the water-soluble tastants, allowing them to bind to receptor cells. The receptor cells pass electrical signals to the brain with information about the taste.

References

Journal article

Soft and ion-conducting hydrogel artificial tongue for astringency perception

Science Advances

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