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


  • Flexible
  • Increased sensitivity


  • 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 polymer 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.

Image: Jeonghee Yeom / Ulsan National Institute of Science and Technology / Copyright © ‑ All rights reserved

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

Biomimicry Story

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.