Blood–brain mechanics: How brain tissue responds to pulsatile blood flow dynamics

Highly coupled interactions between nonlinear fluids and soft matter are ubiquitous in nature and critical for various applications. A prime example is the blood–brain interaction, where the pulsatile non-Newtonian blood flow deforms the extremely soft and highly nonlinear human brain tissues. Understanding this dynamic is vital, as it can provide critical insights into neurological issues and their underlying mechanisms. However, experimentally investigating these interactions is less feasible due to the limited access to the human brain. Although advanced computational models have been developed to simulate blood flow in the human brain, a comprehensive model that can reconcile the various nonlinear components in a fully coupled framework to capture the specific interactions between the blood flow, vessel movement, and brain tissue dynamics remains elusive.

To explore the mechanisms governing blood–brain interactions, we have developed an innovative finite element model that seamlessly integrates the interactions between non-Newtonian blood flow, hyperelastic blood vessels, and hyper-viscoelastic brain tissue. This model is enhanced by a hyper-viscoelastic model based on compression–relaxation tests of human brain tissues, which can precisely capture their time-dependent nonlinear behaviour. Comprehensive simulations based on this model illustrate how pulsatile blood flow significantly deforms brain tissues under various scenarios. This study not only offers new possibilities for understanding the intimate links between brain function and its biomechanics, but also provides a novel modelling framework to solve complex interactions between nonlinear fluids and soft matter across several other scientific disciplines and fields.