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Issue 25, 2019
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Poynting effect of brain matter in torsion

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Abstract

We investigate experimentally and model theoretically the mechanical behaviour of brain matter in torsion. Using a strain-controlled rheometer, we perform torsion tests on fresh porcine brain samples. We quantify the torque and the normal force required to twist a cylindrical sample at constant twist rate. Data fitting gives a mean value for the shear modulus of μ = 900 ± 312 Pa and for the second Mooney–Rivlin parameter of c2 = 297 ± 189 Pa, indicative of extreme softness. Our results show that brain always displays a positive Poynting effect; in other words, it expands in the direction perpendicular to the plane of twisting. We validate the experiments with finite element simulations and show that when a human head experiences a twisting motion in the horizontal plane, the brain can experience large forces in the axial direction.

Graphical abstract: Poynting effect of brain matter in torsion

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Publication details

The article was received on 18 Jan 2019, accepted on 30 Apr 2019 and first published on 13 Jun 2019


Article type: Paper
DOI: 10.1039/C9SM00131J
Soft Matter, 2019,15, 5147-5153
  • Open access: Creative Commons BY license
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    Poynting effect of brain matter in torsion

    V. Balbi, A. Trotta, M. Destrade and A. Ní Annaidh, Soft Matter, 2019, 15, 5147
    DOI: 10.1039/C9SM00131J

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