Printed tongues take some licking

British scientists have 3D-printed some rather sophisticated fake tongues – even if they don’t actually look like tongues.

In a paper in the journal ACS Applied Materials & Interfaces, they describe creating synthetic silicone structures that realistically mimic the topology, elasticity and “wettability” of the real thing.

These factors are instrumental in how food or saliva interacts with the tongue, they say, which in turn can affect mouthfeel, swallowing, speech, nutritional intake and quality of life.

And that explains why they did it. They suggest that a biomimetic tongue could help test oral processing properties of food, nutritional technologies, pharmaceutics and dry mouth therapies without the need for expensive and time-consuming early-stage human trials.

It might also assist in better understanding how fluids interact within the oral cavity, and with testing around food safety.

The work was led by the University of Leeds, in collaboration with the University of Edinburgh, and brought together specialists in food colloid science, soft matter physics, dentistry, mechanical engineering and computer science.

It came with “unique architectural challenges,” according to lead author Efren Andablo-Reyes, because of the hundreds of bud-like papillae that give the tongue “a complicated landscape from a mechanical perspective”.

“We focused our attention on the anterior dorsal section of the tongue where some of these papillae contain taste receptors, while many of them lack such receptors,” he says.

“Both kinds of papillae play a critical role in providing the right mechanical friction to aid food processing in the mouth with the adequate amount saliva, providing pleasurable mouthfeel perception and proper lubrication for swallowing.”

The team took silicone impressions of tongue surfaces from 15 adults, scanned them to map papillae dimensions, density and the average roughness, then used computer simulations and mathematical modelling to create a 3D-printed artificial mould.

Papillae were found to have a random distribution, which “appears to play an important sensory role for the tongue”, according to Edinburgh’s Rik Sarkar, a co-author.

The artificial surface was then 3D printed using digital light processing technology, and a series of experiments run using different complex fluids to ensure the surface’s wettability – how a liquid keeps contact and spreads across a surface – and the lubrication performance was the same as the human tongue impressions.

“The application of bio-tribological principles, the study of friction and lubrication, in the creation of this tongue-like surface is a significant step forward in this field,” says co-author Michael Bryant, from Leeds.

“The ability to produce accurate replicas of tongue surfaces with similar structure and mechanical properties will help streamline research and development for oral care, food products and therapeutic technologies.”