Soft and ion-conducting hydrogel artificial tongue for astringency perception

Artificial tongues have received increased attention due to their ability to detect the five basic tastes, but until now scientists have been unable to fully enable human tongue-like biomimicry for astringency in the lab. To mimic the mechanisms of human tongue-like perception of astringency, Jeonghee Yeom and a team of scientists in energy engineering and chemical engineering at the Ulsan National Institute of Science and Technology in the Republic of Korea, used a saliva-like, chemiresistive ionic hydrogel anchored to a flexible substrate to create a soft artificial tongue. They exposed the construct to astringent compounds and allowed hydrophobic aggregates to form in the microporous network, transforming it into a micro/nanoporous structure with improved ionic conductivity. Using the unique human tongue-like structure, they detected tannic acid (TA) across a wide spectrum (0.0005 to 1 weight percentage) with high sensitivity and a fast response time. As a proof-of-concept, the sensor detected the degree of astringency in beverages and fruits based on a simple wipe-and-detect method. The platform will have powerful future applications in humanoid robots and as taste monitoring devices, the research work is now published on Science Advances.