Issue 25, 2019

Poynting effect of brain matter in torsion

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

Supplementary files

Article information

Article type
Paper
Submitted
18 Jan 2019
Accepted
30 Apr 2019
First published
13 Jun 2019
This article is Open Access
Creative Commons BY license

Soft Matter, 2019,15, 5147-5153

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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