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。在爆炸和汽车碰撞等事件中，大脑的快速变形会导致创伤性脑损伤。了解人类大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。设计更安全的个人防护设备以及脑损伤管理和预防策略也需要这些知识。不幸的是，目前对人类大脑的机械行为的理解仅限于微小的变形和狭窄的加载速率范围，这并不能代表造成伤害的全部条件。该奖项支持结合高速机械测试、分析和计算建模以及机器学习的基础研究，以深入了解活体人脑如何对大型快速负载做出反应。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，并将为组织力学、创伤性脑损伤和机器学习领域做出贡献。该项目将开设新课程，并涉及代表性不足的少数民族的贡献。本研究的首要目标是了解大脑在其原生生物物理环境中的高应变率机制。第一阶段将集中在小变形和动态应变率下的组织反应。宽带磁共振弹性成像实验将在多个脑区脑组织标本上进行，建立线性粘弹性本构模型。将开发多保真度模型，将观察到的响应与可用的窄带体内脑组织响应融合在一起，以预测体内脑组织在宽加载频率范围内的线性粘弹性特性。第二阶段将集中在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。将开发基于物理的多保真度模型，以融合前一阶段表征的离体粘弹性响应和体内线性粘弹性响应。这项研究将通过深入了解体内和离体组织力学之间的关系，以及有史以来第一次在极端负载条件下适用的活体大脑力学特性的全景图，显著推进我们对大脑生物力学的理解。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值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.