CAREER: Dynamics and Damage of Void Collapse in Biological Materials Under Stress Wave Loading

主要研究员：乔安娜·奥斯汀研究所：伊尔巴纳大学香槟分校提案编号：CBET-0954769摘要塌陷空洞在从生物医学到水下推进再到炸药的各种应用中都会造成广泛的损害。虽然对冲击引起的空洞坍塌有广泛的研究，但如果存在波的衰减机制或冲击速度相对较低，则会发生应力波加载。本研究的目的是量化加载波形对多孔洞坍塌的水动力相互作用和损伤机制的影响。在分布载荷下，波的分布与空洞和空洞间的长度尺度是相似的，这可能会导致强耦合的相互作用，并排除了冲击波坍塌模型的直接应用，例如在生物医学应用中预测细胞和组织损伤。脉冲激光诱导的组织和细胞破坏可以带来巨大的生物医学治疗益处，例如在延缓肿瘤生长方面，然而，也可能导致对周围组织的严重附带损害。创伤的一种机制是空洞对压力脉冲的动态响应，通过与体内声学异质性的相互作用，随着上升时间的增加，空洞从初始冲击中衰减。在这些加载条件下的组织损伤预测模型对于使用这些强大的技术至关重要。智能优点：动态实验旨在强调空洞在应力波通过后坍塌的相互作用和损伤机制。在生物医学应用中，与峰值压力相比，斜波轮廓(或上升时间)与组织损伤的相关性更好。据PI所知，在这些条件下空洞的坍塌以前还没有被研究过。将在模型实验装置中进行空洞坍塌的实验时间分辨可视化、周围材料中的第一次速度场测量以及内部和外部温度测量，该模型实验装置允许在组织替代聚合物材料中准确放置2D和3D空洞阵列。PI的初步工作表明，内部体积历史是非线性的，这与模拟一致，但与现有的线性实验数据吻合。上升时间的作用将作为整个波浪的总体压力比的附加参数进行检验。在多个空洞的情况下，速度测量显示应力波绕射响应于上游空洞，影响随后的加载条件。崩塌抑制(屏蔽)和崩塌触发效应都被观察到，并将被量化。布罗德影响准确预测组织和细胞损伤的能力对广泛的生物医学应用中的治疗选择产生深远影响，包括体外冲击波碎石术、激光诱导等离子体手术和超声波。通过将研究成果融入到当地社区儿童、中学生和本科生三个年龄段的活动中，职业研究和教育计划相互交织在一起。通过这个综合研究和教育计划，本科生将接触到跨学科的学习，并将向中学生展示他们的研究成果，特别是通过女孩在数学、工程和科学(游戏)和女孩做科学项目中的机会。这些项目的目标是中学阶段的女孩，而在这个阶段，学术环境中的自尊大幅下降已被广泛报道。航空航天工程游戏计划目前正在由PI与伊利诺伊州工程学院协调开发。主要目标是通过展示工程学的社会有效性、机会广度和社区利益，以及通过团队项目、接触大学以及与榜样和导师会面来提供学习机会，从而留住在数学和科学方面有学术天赋的中学女生。该协会还将继续她在招聘和指导工程学本科生和研究生方面的成功记录，以及继续参与诸如Girls do Science等外展活动。

Title: CAREER: Dynamics and Damage of Void Collapse in Biological Materials Under Stress Wave LoadingPrincipal Investigator: Joanna AustinInstitution: U of Ill Urbana-ChampaignProposal No: CBET-0954769AbstractCollapsing voids cause extensive damage in diverse applications from biomedicine to underwater propulsion to explosives. While there is extensive research into shock induced void collapse, if there are mechanisms for wave attenuation or if the impact velocity is relatively low, stress wave loading will instead occur. The objective of this research is to quantify the effect of loading wave profile on the hydrodynamic interaction and damage mechanisms of multiple void collapse. Under distributed loading, the wave profile and void and inter-void length scales can be comparable, potentially resulting in a strongly coupled interaction and precluding the direct application of shock wave collapse models, for example to predict cell and tissue injury in biomedical applications. Tissue and cell destruction by pulsed laser induced waves can have enormous biomedical treatment benefits for example in retards to cancerous tumor growth, however, severe collateral damage of surrounding tissue can also result. One mechanism for trauma is the dynamic response of voids subjected to the pressure pulse, which is attenuated from an initial shock with an increase in rise time by interaction with acoustic heterogeneities in the body. Predictive models for tissue damage under these loading conditions are critical to the use of these powerful techniques.Intellectual Merit:Dynamic experiments are designed to highlight the interaction and damage mechanisms of voids collapsing after passage of a stress wave. In biomedical applications, the ramped wave profile (or rise time) is found to correlate better with tissue damage than the peak pressure. To the PI's knowledge, the collapse of voids under these conditions has not been previously studied. Experimental time resolved visualizations of void collapse, the first velocity field measurements in the surrounding material, and internal and external temperature measurements will be carried out in a model experimental setup which allows accurate placement of 2D and 3D void arrays in a tissue surrogate polymer material. Initial work by the PI has shown the internal volume history is nonlinear, in agreement with simulations but in contrast to existing linear experimental data fits. The role of rise time will be examined as additional parameter to the overall pressure ratio across the wave. In the case of multiple voids, velocity measurements show the stress wave diffracts in response to the upstream void, affecting the subsequent loading condition. Both collapse-inhibiting (shielding) and collapse triggering effects are observed and will be quantified.Broader impacts The capability for accurate prediction of tissue and cellular damage has a profound impact on treatment options across a broad range of biomedical applications including extracorporeal shock wave lithotripsy, laser induced plasma surgery, and ultrasound. The CAREER research and educational plans are interwoven through the incorporation of research results in hands on activities that reach three age groups: local community children, middle school students, and undergraduate students.Through this integrated research and education plan, undergraduate students will be exposed to interdisciplinary study and will showcase their research results to demonstrate opportunities to middle school students, particularly through the Girls Adventures in Mathematics, Engineering, and Science (GAMES)and Girls Do Science programs. These programs target girls at middle school age level, when a dramatic decrease in self esteem in academic settings has been widely reported. The Aerospace Engineering GAMES program is currently being developed by the PI in coordination with the College of Engineering at Illinois. The overarching goal is retention of academically talented middle school girls in math and science by demonstrating the social validity, breadth of opportunity, and the community benefits of engineering, and by providing the opportunity for learning through team based projects, exposure to the University, and meetings with role models and mentors. The PI will also continue her successful record of recruiting and mentoring undergraduate and graduate students in engineering, as well as on going participation in outreach activities such as Girls Do Science.