#Tongue note recorder portable#

During the complexation process, substantial tension is applied to the micropores, resulting in tearing off the original pore walls by the generation of hydrophobic linkages. Furthermore, self-association via hydrogen bonding leads to much larger hydrophobic aggregates inside the polymer matrix.

Coupling between mucin and a sufficient number of phenolic hydroxyl groups of TA enables TA to surround mucin and generate hydrophobic mucin-TA complexes (dimers or trimers). In the same manner as the human oral cavity, TA, a specific type of tannin, forms insoluble mucin-TA complexes through hydrophobic interactions between the aromatic rings of TA and hydrophobic amino acid domains of mucin, and hydrogen bonding of hydroxyl groups of TA with carbonyl and amide groups of mucin ( 17). Inspired by the sensing mechanism of oral dryness caused by astringent tastants, we designed a soft hydrogel–based artificial tongue, which is a saliva-like ionic PAAm hydrogel containing mucin proteins and LiCl electrolytes ( Fig.

#Tongue note recorder portable#

In addition, the astringency sensor array acts as a portable taste mapping tool to detect degree of astringency and exposed location simultaneously. Furthermore, our flexible astringency sensors can detect the degree of astringency in real beverages and monitor the ripening of fruits using a simple wipe-and-detection method. The artificial tongue exhibited a wide sensing range for TA, high sensitivity (0.292 wt % −1), and fast response time (~10 s). When TA solution diffuses into the hydrogel matrix, incoming TA molecules bind and complex with the mucin to form hydrophobic aggregates and further transform the microporous hydrogel into the hierarchical micro/nanoporous structure, resulting in enhanced ionic conductivity. As a representative polyphenolic substance, tannic acid (TA) is used ( 15, 16). The thickness of the soft hydrogel (200 μm) is comparable to that of an actual salivary layer on a human tongue efficient adsorption and diffusion of astringent compounds inside the hydrogel occur.

The artificial tongue consists of mucin as secreted protein, lithium chloride (LiCl) as electrolyte, and polyacrylamide (PAAm) as the three-dimensional (3D) porous polymer network for the facile flow of electrolyte. Inspired by the thin salivary layer on the tongue, a soft and thin hydrogel film is integrated on a flexible polymer substrate through covalent bonding. Here, mimicking the mechanism of human astringency perception, we introduce a soft hydrogel–based artificial tongue. Moreover, to the best of our knowledge, demonstration of a fully flexible and soft artificial tongue that is highly selective to specific astringent tastants has not been achieved. The unique sensing mechanism of astringency is based on indirect stimulation of mechanoreceptors residing in the ruptured salivary film, which consequently leads to the rare demonstration of artificial tongue for astringency based on specific target-binding methods. When astringent tastants enter the oral cavity, they bind with secreted proteins to form insoluble precipitates on the tongue, resulting in shrinkage of the epithelium that causes dryness and a puckering feeling in the mouth.

Astringency is perceived by the strong association of ingested astringent tastants and saliva proteins covering the tongue ( 14). Polyphenols are beneficial as strong antioxidant and anti-inflammatory substances ( 12), but they may also provoke negative nutritional impacts that can often be lethal when high doses are consumed ( 13).

As a proof of concept, 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.Īstringency is stimulated by exposure to polyphenols, which are mainly found in unripe fruits, wines, and tea. This unique human tongue–like performance enables tannic acid to be detected over a wide range (0.0005 to 1 wt %) with high sensitivity (0.292 wt % −1) and fast response time (~10 s). When exposed to astringent compounds, hydrophobic aggregates form inside the microporous network and transform it into a micro/nanoporous structure with enhanced ionic conductivity. Mimicking the mechanism of astringency perception on the human tongue, we use a saliva-like chemiresistive ionic hydrogel anchored to a flexible substrate as a soft artificial tongue. However, it is still challenging to fully mimic human tongue–like performance for tastes such as astringency. Artificial tongues have been receiving increasing attention for the perception of five basic tastes.