Astringency is stimulated by exposure to polyphenols, which are mainly found in unripe fruits, wines, and tea. A research team led by Ko Hyun-hyub, a professor of energy and chemical engineering at Ulsan National Institute of Science and Technology (UNIST), has developed an astringent sensor using a saliva-like chemiresistive ionic hydrogel anchored to a flexible substrate as a soft artificial tongue.
"It is easy to produce and there is no complicated process of preparing specimen for analysis, so it can be applied to various fields, including agriculture, as well as food and liquor industries," Ko said.
Inspired by the thin salivary layer on the tongue, a soft and thin hydrogel film was integrated on a flexible polymer substrate through covalent bonding, Ko's team said in a research paper published on the website of Science Advances, a peer-reviewed science journal
When exposed to astringent compounds, hydrophobic aggregates form inside the microporous network and transform it into a micro/nanoporous structure with enhanced ionic conductivity, the research team said, adding the unique human tongue–like performance enables tannic acid to be detected over a wide range with high sensitivity and fast response time.
"Our sensor can detect the degree of astringency in beverages and fruits using a simple wipe-and-detection method, making a powerful platform for future applications involving humanoid robots and taste monitoring devices," the team said.