Application of biomimetic tongue substrate to investigate the role of friction and vibration in sensory texture perception

This study proposed a novel biomimetic tongue substrate to better understand food texture perception, expanding the scope of this mechanism from merely friction to also include vibration in oral lubrication. With our bioinspired setup, friction and vibration signals were simultaneously acquired using the polyvinyl alcohol (PVA) hydrogel substrates fabricated with different parameters of surface roughness and thickness. Results showed that the feature parameters of friction coefficient and vibration amplitude were positively correlated to surface roughness, while substrate thickness had little effect on these features. Characterization tests were conducted for the PVA biomimetic tongue substrate with featured filiform papillae and fungiform papillae, whose surface roughness, Young's modulus, and friction coefficient were 70.94 ± 8.44 μm, 12.11 ± 1.15 kPa, and 0.17, respectively, showing similar properties and friction responses to the human tongues. Focusing on the typical texture attributes of slipperiness, astringency, and graininess, rheological, friction, and vibration response were further measured using the food samples mixed with artificial saliva. Sensory analysis was also conducted to demonstrate the essential roles of tactile features in sensory texture perception. Results of correlation analysis revealed that sensory slipperiness and astringency had linear correlations with friction coefficient (r = 0.89 and 0.899, respectively), while sensory graininess was linearly correlated with vibration amplitude (r = 0.905, higher than r = 0.819 with friction coefficient). The findings highlighted the crucial role of oral friction and vibration sensation in sensory texture perception. Meanwhile, this work provided a new biomimetic setup for oral lubrication studies, paving the way for a better understanding of the food texture perception mechanism.