Development of an artificial tongue that tastes tartness using a chemically resistant ionic hydrogel similar to saliva. Artificial tongues are increasingly focused on sensing the five basic tastes, including sweet, sour, bitter, salty, and umami. However, it is still a challenge to fully mimic the human tongue-like performance for tastes such as astringency. Mimicking the astringency sensing mechanism of the human tongue, we use a saliva-like chemiresistive ionic hydrogel attached to a flexible substrate as a soft artificial tongue. When exposed to astringent compounds, hydrophobic aggregates form within the microporous network, transforming it into a micro/nanoporous structure with increased ionic conductivity. This unique human tongue-like performance enables the sensing of tannic acid. As a proof of concept, our sensor can detect the level of astringency in beverages and fruits through a simple wipe-and-sense process, creating a powerful platform for future applications involving humanoid robots and taste-monitoring devices.

Innovation details

Specific molecules that cause the perception of astringency are found primarily in unripe fruits, wines, and teas. A thin layer of saliva on the tongue is important for tasting because it absorbs the molecules and allows them to bind to receptor cells that send signals to the brain that the food is astringent. The researchers mimicked this layer of saliva by creating a thin hydrogel layer on top of a 3D-porous polymer network that facilitates the flow of electrolytes. The hydrogel absorbs the molecules that cause astringency, causing them to clump together. This increases the ionic conductivity of the hydrogel, resulting in an increased current that sends a signal that astringent molecules are present.

Inspiration from nature

The tongue is a soft, flexible muscular organ responsible for the sense of taste. The tongue has mechanoreceptors and ion channels that help translate the signals used to perceive taste. In addition, saliva plays a key role in tasting by absorbing water-soluble flavors and allowing them to bind to receptor cells. Receptor cells transmit electrical signals to the brain with information about taste.

Advantages: Flexibility and increased taste perception

Application option: Medical implants and the field of robotics

Sustainable development goals addressed: Health and well-being.

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Summarized by AskNature.org