Constitutive characterization of biological tissues at high strain rates
Abstract
Project Summary/Abstract (Approved for public release)Constitutive characterization of biological tissues at high strain ratesProgram: Naval Force Health Protection ProgramProgram officer: Dr. Timothy BentleyDigital engineering harnesses predictive computational modeling for iterative engineering design that minimizes the need for expensive testing, and this approach has been successfully deployed in the design of complex engineering systems, e.g., vehicles, such as ships and planes. However, this process neglects loads and deformations applied to human occupants, which is a crucial aspect of predicting potential injuries and hence occupant safety. A key impediment to predictive digital engineering involving the mechanical interactions between humans and engineered systems is the high strain-rate constitutive behavior of biological tissues, which are required as an input but remain a source of uncertainty. Therefore, there is a need for improved mechanical characterization of biological tissues over a broad range of strain rates. Calibrated, predictive constitutive models for soft biological tissue materials are currently lacking because applying traditional high strain-ratematerial characterization techniques (e.g., Kolsky bar or Taylor plate-impact testing) to soft materials is challenging. To address this need, a new soft-material characterization technique has been developed using measurements of the dynamics of isolated bubbles generated by laser or acoustic pulses. Using high-speed imaging of the bubble dynamics along with a theoretical cavitation modeling framework provides a route to high strain-rate soft material characterization, and this approach has been shown to be able to discern mechanical properties at previously undocumented strain rates in materials as soft as a few kPa. In the proposed project, this promising approach will be applied to obtaining calibrated high strain-rate constitutive models for several types of biological tissue. Because biological tissues are not optically transparent, laser-induced cavitation experiments will be carried out by collaborators in thin slices of tissue constrained between parallel glass coverslips. The first aim of the proposed project is to develop and validate a robust, finite-element-based numerical framework that will account for the nonlinear interactions between the bubble and the rigid walls in a thin layer of a soft material, leading to a more accurate estimation of the material parameters for soft materials at high strain rates. Validation will be carried out in a benchmark gelatin gel. In the second aim, using data from laser-induced cavitation experiments in tissue from several different anatomical regions of porcine brains (white matter, gray matter, midbrain, hippocampus, etc.) generated by collaborators, numerical simulations of the cavitation process will be performed, and model predictions will be fit to the experimental data in order to determine the high strain-rate constitutive behavior of the different regions of porcine brain tissue. This process will also be applied to additional porcine tissues, moving first to kidney and next toliver. Successful completion of the proposed fundamental research would result in a validated, extended version of IMR that is applicableto cavitation in thin layers, so that IMR may be applied to materials that are not optically transparent and provide the first set of robust, large-strain, high strain-rate material properties for biological tissues. This material property data will enable predictive digital engineering, potentially leading to improved strategies for mitigating and preventing injuries both in the armed forcesand amongst civilians (e.g., in sports-related injuries).
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- May 15, 2023
- Source ID
- N000142312519
Entities
People
- David L. Henann
Organizations
- Brown University
- Office of Naval Research
- United States Navy