UK scientists led by the University of Leeds in collaboration with the University of Edinburgh have replicated the highly sophisticated surface design of a human tongue and demonstrated that their printed synthetic silicone structure mimics the topology, elasticity and wettability of the tongue's surface.
A biomimetic tongue will help developers to perform screening of newly designed products and accelerate the new development processes without the necessity of human trials at early stages that are often very expensive and time consuming.
The 3D printed negative mould showing holes for the filiform and fungiform papillae
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Particularly, since the onset of the COVID-19 pandemic, social distancing has posed significant challenges to carry out such sensory trials and consumer tests. A biomimetic tongue will be immensely helpful to increase development productivity and reducing manufacturers' reliance on human trials in the early stages.
Study lead author, Dr Efren Andablo-Reyes conducted this research while a postdoctoral fellow in the School of Food Science and Nutrition at Leeds. He said: "Recreating the surface of an average human tongue comes with unique architectural challenges. Hundreds of small bud-like structures called papilla give the tongue its characteristic rough texture that in combination to the soft nature of the tissue create 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. The study that brought together unique expertise in food colloid science, soft matter physics, dentistry, mechanical engineering and computer science is published today in the journal ACS Applied Materials & Interfaces.
The team took silicone impressions of tongue surfaces from fifteen adults. The impressions were 3D optically scanned to map papillae dimensions, density and the average roughness of the tongues. The texture of a human tongue was found to resemble a random layout.
The team used computer simulations and mathematical modelling to create a 3D-printed artificial surface to function as a mould containing wells with the shape and dimensions of the different papillae randomly distributed across the surface with right density. This was replica-moulded against elastomers of optimised softness and wettability.
University of Edinburgh co-author, Rik Sarkar of the School of Informatics said: "We defined a new concept called collision probability to measure mechanosensing that will have large impact in this area. In the future, we will use a combination of machine learning and computational topology to create tongue models of diverse healthy and diseased individuals to address various oral conditions."
The artificial surface was then 3D printed using digital light processing technology based in the School of Mechanical Engineering at Leeds. The team ran a series of experiments using different complex fluids to ensure that the printed surface's wettability and the lubrication performance was the same as the human tongue impressions.
Principal Investigator Anwesha Sarkar, Professor of Colloids and Surfaces at Leeds, said: "Accurately mapping and replicating the tongues surface and combining that with a material that approximates the elasticity of human tongue was no small task. Harnessing expertise from multiple STEM disciplines, we've demonstrated the unprecedented capability of a 3D printed silicone surface to mimic the mechanical performance of the human tongue.
We believe that fabricating a synthetic surface with relevant properties that mimics the intricate architectural features, and more importantly the lubricating performance of the human tongue is paramount to gaining quantitative understanding of how fluids interact within the oral cavity."