Biomimetic tongue. University of Leeds
For the first time, scientists have used 3D printing to create synthetic soft surfaces with tongue-like textures that open up new possibilities for testing the oral processing properties of food, nutritional technologies, pharmaceuticals, and dry mouth therapies.
British scientists, led by the University of Leeds in collaboration with the University of Edinburgh, have recreated the sophisticated surface design of a human tongue and demonstrated that its printed synthetic silicone structure mimics the topology, elasticity and wettability of the tongue surface.
These factors play important roles in how food or saliva interacts with the tongue, which in turn can affect mouthfeel, swallowing, language, food intake, and quality of life.
Biomimetic language helps developers screen newly developed products and accelerate the new development processes without the need for early-stage human testing, which is often very expensive and time-consuming.
The 3D printed negative form shows holes for the filiform and fungiform papillae. Photo credit: University of Leeds
Especially since the beginning of the COVID-19 Pandemic social distancing has posed significant challenges in conducting such sensory and consumer testing. Biomimetic language will be immensely helpful in increasing development productivity and reducing manufacturers’ reliance on human studies at an early stage.
A biomimetic tongue could also have myriad uses for combating adulteration in food and other orally administered drugs, whether or not texture attributes can determine traits and save huge economic losses.
The complexity of the tongue’s biological surface has posed challenges for artificial replication and has significantly hampered the development and screening of effective, long-lasting treatments or therapies for dry mouth syndrome – approximately 10% of the general population and 30% of the elderly suffer from dry mouth.
3D optical image near the tip of the human tongue surface. Photo credit: Anwesha Sakar, University of Leeds
The study’s lead author, Dr. Efren Andablo-Reyes, did this research as a postdoctoral fellow at the School of Food Science and Nutrition in Leeds. He said, “Restoring the surface of an average human language poses unique architectural challenges. Hundreds of small, bud-like structures called papillae give the tongue its characteristic rough texture which, when combined with the soft nature of the tissue, creates an intricate landscape from a mechanical point of view.
“We turned our attention to the front of the tongue, where some of these papillae contain taste receptors, while many of them lack such receptors. Both types of papillae play a vital role in providing the proper mechanical friction to aid in mouth food processing with the proper amount of saliva, a comfortable mouthfeel, and adequate lubrication for swallowing.
“We wanted to reproduce these mechanically relevant properties of the human tongue on a surface that is easy to use in the laboratory to replicate oral processing conditions.”
The study, which brought together unique expertise in food colloid science, soft matter physics, dentistry, mechanical engineering, and computer science, is published in the journal today ACS Applied Materials & Interfaces.
The team took silicone impressions of the tongue surfaces of fifteen adults. The impressions were optically 3D scanned to map the papillary dimensions, density and average roughness of the tongues. The texture of a human tongue has been found to resemble a random layout.
The team used computer simulations and mathematical models to create a 3D printed artificial surface that will serve as a shape and contain depressions with the shape and dimensions of the various papillae, randomly distributed over the surface at the correct density. This has been simulated against elastomers with optimized softness and wettability.
University of Edinburgh co-author Rik Sarkar of the School of Informatics said: “The randomness in the distribution of papillae appears to play an important sensory role in the tongue.
“We have defined a new concept called the likelihood of collision to measure the mechanosensing, which will have a major impact in this area. In the future, we’ll be using a combination of machine learning and computer topology to create tongue models of various healthy and sick people to address various oral diseases. ”
The artificial surface was then 3D printed using digital light processing technology at the School of Mechanical Engineering in Leeds.
The team carried out a series of experiments with various complex liquids to ensure that the wettability of the printed surface – like a liquid, maintains contact and spreads over a surface – and the lubricity performance matched the imprints of the human tongue.
The co-author Dr. Michael Bryant of the Leeds School of Mechanical Engineering said, “The application of bio-tribological principles, the study of friction and lubrication in creating this tongue-like surface is a significant advance in this area.
“The ability to create accurate replicas of tongue surfaces with similar structure and mechanical properties will help streamline research and development in oral care, food and therapeutic technologies.”
Principal researcher Anwesha Sarkar, Professor of Colloids and Surfaces in Leeds, said: “Accurately mapping and replicating the tongue surface and combining it with a material that approximates the elasticity of the human tongue was no easy task. We leveraged the expertise of several STEM disciplines and demonstrated the unparalleled ability of a 3D printed silicone surface to mimic the mechanical performance of the human tongue.
“We believe that creating a synthetic surface with relevant properties that mimic the intricate architectural features and, most importantly, the lubricating performance of the human tongue is of paramount importance in order to gain a quantitative understanding of the interaction of fluids in the oral cavity.
“This biomimetic tongue surface could also serve as a unique mechanical tool to detect counterfeiting in food and premium beverages based on texture attributes. This is a global problem and can help ensure food safety.
“Ultimately, we hope the surface we design can be important in understanding how the biomechanics of the tongue underpins the foundations of human nutrition and language.
Reference: “3D Biomimetic Tongue Emulating Surfaces for Tribological Applications” by Efren Andablo-Reyes, Michael Bryant, Anne Neville, Paul Hyde, Rik Sarkar, Mathew Francis and Anwesha Sarkar, October 27, 2020, ACS Applied Materials & Interfaces.
DOI: 10.1021 / acsami.0c12925
This project was funded by the European Research Council (ERC) as part of the European Union’s Horizon 2020 research and innovation program.
