Collaborative Research: Extreme Mechanics of the Human Brain via Integrated In Vivo and Ex Vivo Mechanical Experiments

人脑表现出复杂的机械行为。它在外力作用下的变形取决于加载的程度和速度。在爆炸和车祸等事件中，大脑迅速变形可能会导致创伤性脑损伤。了解人脑在这种极端条件下的机械行为，对于开发预测脑损伤的计算机模型至关重要。这些知识也是设计更安全的个人防护装备和脑损伤管理和预防战略所必需的。不幸的是，目前对活人大脑机械行为的了解仅限于微小的变形和狭窄的加载速率范围，并不能代表造成伤害的全部条件。该奖项支持结合高速率机械测试、分析和计算建模以及机器学习的基础研究，以深入了解活着的人脑如何应对大规模和快速的负载。这项研究的结果将对美国国民的健康和福利产生积极影响，并将对组织力学、创伤性脑损伤和机器学习领域做出贡献。这个项目将导致新的课程，并涉及代表不足的少数民族的贡献。这项研究的总体目标是了解大脑在其本地生物物理环境中的高应变率机制。第一阶段将重点研究小变形和动态应变率下的组织反应。将对来自多个脑区的脑组织标本进行宽带磁共振弹性成像实验，以建立线性粘弹性本构模型。多保真模型将被开发来融合观察到的响应和可用的窄带活体脑组织响应，以预测在大范围加载频率下活体脑组织的线性粘弹性特性。第二阶段将重点研究大变形和极端应变率下的组织反应。将进行准静态和动态力学试验，以建立粘超弹性本构模型。物理信息的多保真模型将被开发，以融合体外粘超弹性反应和在体的线性粘弹性反应，在前一阶段表征。这项研究将极大地促进我们对大脑生物力学的理解，通过深入了解体内和体外组织力学之间的关系，以及首次在极端负荷条件下适用的活体大脑机械特性的全场图。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

The human brain exhibits complex mechanical behavior. Its deformation under external forces depends on the extent and speed of loading. Rapid deformation of the brain during events such as blasts and automotive crashes can cause traumatic brain injury. Understanding the mechanical behavior of the human brain under such extreme conditions is critical to developing computer models for predicting brain injury. This knowledge is also needed to design safer personal protective equipment and brain injury management and prevention strategies. Unfortunately, the current understanding of the mechanical behavior of living humans' brains is restricted to small deformations and a narrow range of loading rates that do not represent the full spectrum of injury-causing conditions. This award supports fundamental research combining high-rate mechanical testing, analytical and computational modeling, and machine learning to generate insights into how the living human brain responds to large and rapid loading. Results from this research will positively impact U.S. national health and welfare and will contribute to the fields of tissue mechanics, traumatic brain injury, and machine learning. This project will lead to new courses and involve contributions from underrepresented minorities.The overarching goal of this research is to understand the high strain rate mechanics of the brain in its native biophysical environment. The first stage will focus on tissue responses under small deformations and dynamic strain rates. Wide-band Magnetic Resonance Elastography experiments will be conducted on brain tissue specimens from multiple brain regions to develop linear viscoelastic constitutive models. Multi-fidelity models will be developed to fuse the observed responses with available narrow-band in vivo brain tissue responses for predicting linear viscoelastic properties of the in vivo brain tissue in a wide range of loading frequencies. The second stage will focus on tissue responses under large deformations and extreme strain rates. Quasi-static and dynamic mechanical testing will be conducted to develop visco-hyperelastic constitutive models. Physics-informed multi-fidelity models will be developed to fuse the ex vivo visco-hyperelastic responses with the in vivo linear viscoelastic responses characterized in the previous stage. This study will significantly advance our understanding of brain biomechanics by generating insights into the relationship between in vivo and ex vivo tissue mechanics and the first-ever full-field maps of the living brain’s mechanical properties applicable under extreme loading conditions.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.