Master 2
Approche biomimétique de la perception de textures en bouche

As part of a contract with Nestec Ltd (Nestlé Rese arch Center), we are seeking a Master student to work on in - mouth texture perception using a biomimetic approach.

Recent psychophys ical tests by Nestlé, designed to study mouth feel of emulsions , have revealed that human subjects can perceive minute changes in the droplet density within emulsions, where standard rheological measurements show no significant differences in shear viscosity.

It is thought that two different biomechanical processes could underlie such remarkable discrimination tasks. First, the softness of the tongue tissue may induce non - trivial rheological responses owing to the coupling between the shear - induced normal stress and the tongue deformation s . Second, the micro - droplets may interlock with the tongue’s topography ( papillae ) and thus modify the effective lu brication efficiency of the emulsion. Both biomechanical aspects of the tongue could prove important in shaping the surface stress signal s that drive the texture perception.

To address these questions, we are currently using a biomimetic approach that co nsists in reproducing the functioning of the human tongue/palate system. The artificial tongue is made of a soft elastomer slab covered with myriads of cylindrical asperities of the same material, as equivalents of the filliform papillae ( see pictures abov e for an extended (left) and a close up (right) view ). The artificial tongue is placed at the bottom of the cell of a rhe oscope (rheometer combined with a microscope) , whose rotating disk plays the equivalent of the palate. We have developed image correlation techniques to measure the deflections of cylindrical papillae when shearing occurs.

In this internship, we will study the papillae’s response when m icro - emulsions or granular suspensions are sheared in a plane - plane geometry. From Einstein’s l aw, one expects that the viscosity increases linearly with the droplet density. We will check this law both macroscopically with the rheometer and locally with the papillae’ s average bending.

The student involved in this project will acquire experimental skills in opti cs, rheology and hydrodynamics . He/She will also benefit from strong interactions with the Nestlé Research Center.

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