Scientists have fabricated synthetic soft surfaces, mimicking the texture of the tongue through 3D printing technologies - opening a wide variety of potential applications in food, nutrition, pharmaceutics, and other oral-related studies.
A research team led by scientists from the University of Leeds and the University of Edinburgh in the United Kingdom were able to replicate the complex surface design of a human tongue. They demonstrated in their study that the 3D printed synthetic silicone structure was able to imitate the topology, elasticity, and wettability - or its ability to retain liquids on its surface - of a human tongue.
These are the properties that affect the behavior of saliva or food as it touches the tongue, affecting the sensation in the mouth and the swallowing mechanism, as well as speech and quality of life.
3D Printing a Biomimetic Tongue
One of the urgent and significant applications of a biomimetic tongue, or a synthetic material that emulates the tongue, is in helping overcome the sensory disabilities caused by the global coronavirus pandemic. Sensory trials and consumer tests for experimental medication would see great progress, increasing development productivity for researchers and reducing the pharmaceuticals' reliance on human trials.
A setup that can emulate the human mouth, complete with a lifelike tongue, will allow developers from different fields to conduct screening of products without the need for actual human volunteers in the early stages, which is both costly and time-consuming.
The human tongue, one of the strongest and most versatile muscles in the human body, is both strong and elastic - allowing us to eat and speak. However, the complex composition of its surface has made attempts to synthetically replicate the tongue a challenging task. It adds obstacles in screening and developing effective remedies for dry mouth syndrome - a condition that affects 10 percent of the general population and about a third of older people.
"Recreating the surface of an average human tongue comes with unique architectural challenges," explains Dr. Efren Andablo Reyes, lead author of the study from the School of Food Science and Nutrition at Leeds. He explains that the characteristic rough texture of the tongue is from the papilla - small, bud-like structures - giving rise to the mechanically challenging surface.
Replicating From Actual Tongue Imprints
In the attempt at fabricating a mimetic human tongue, researchers took silicone impressions of the tongue surfaces of fifteen adults. The researchers then conducted 3D optical scanning on the tongue imprints, characterizing properties such as the density, roughness, and the mapping of papillae dimensions.
With the aid of computer simulations and mathematical modelling, researchers fabricated the 3D printed surface which served as the mold for the actual synthetic tongue. The mold also included wells, or impressions in the shape and dimensions of the papillae from the imprints - randomly distributing them while maintaining their density across the tongue. Researchers then created a replica against elastomers to determine the optimal softness and wettability.
"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," Andablo-Reyes explained. While both types of papillae are important in providing the "right mechanical friction" to support food processing with just the right amount of saliva.
