Yi Liu, Ph.D.
Biomedical Engineering Department
723 W. Michigan St. SL 220P
Indianapolis, IN 46202
Ph.D. Applied Mechanics, the University of Pennsylvania, Philadelphia, USA (2003)
M.S. Solid Mechanics, Peking University, Beijing, China (1998)
Department of Biomedical Engineering, University of California, Irvine, California, USA (2005-2006)
Department of Radiology, Iowa University Hospitals and Clinics, Iowa, USA (2003-2005)
Research area : cardiovascular mechanics, microstructure, finite element
My research focuses on the solid mechanics of the heart and vessels. The mechanical properties of myocardium and vessel tissue change with the age and health condition. For example, in ischemia, the myocardium becomes stiff due to loss of blood supply with the subsequent development of fibrosis. In hypertension, there are significant remodeling that change the mechanical properties of the intima, media and adventitia layers of the vessel. We are developing an experimental and computational framework that includes the following main research topics:
Laboratory research and experimental methodologies
- To develop a constitutive model of the nonlinear finite-strain viscoelastic behavior of myocardium and vessel tissue based on the microstructures, including elastin and collagen fibers, fiber cells and smooth muscle cells, which are accurately measured with Multi-Photon Microscopy.
- To combine the above microstructural constitutive model with finite element method, and conduct multiple scale simulations on heart and vessel in different physiological conditions. Our objective is to clarify some important issues in cardiovascular mechanics, including uniform transmural stress hypothesis, the relation between stress/strain and remodeling, the change of myofiber architecture in infarcted heart.
- To develop dynamic cardiovascular elastography method to identify the mechanical properties of myocardium and vessel tissue from biomedical image of the heart and vessel. The result of this in vivo study may serve to diagnose cardiovascular diseases and monitor the therapies, and patient-based surgical simulations.
- Multi-Photon Microscopy (MPM). MPM selectivity is driven by two primary types of nonlinear interaction between ultra-fast laser light and biological tissues: two-photon excited fluorescence and second-harmonic generation. We use MPM to image the elastin and collagen fibers in the vessel wall.
- Triaxial mechanics testing machine. We use step motor-controlled machine to text the mechanical response of vessel segment under inflation, extension and torsion loadings.
- Multiple-scale finite element method. We use multiple-scale finite element method to simulate the macroscopic stress-strain relation of the vessel and the microscopic mechanical response of the cells and fibers.
Wang Z, Liu Y, Sun L, Wang G, Fajardo LL. Elasto-mammography: Theory, Algorithm, and Phantom Study. International Journal of Biomedical Imaging, Vol. 1, 53050-1-11, 2006
Ju JW, Weng L, Liu Y. Ultrasonic frequency-dependent amplitude attenuation characteristics technique for NDE of concrete. ACI Materials Journal, Vol. 103, 177-185, 2006
Liu Y, Wang G, Sun L. Tomography-based 3-D anisotropic elastography using boundary measurements. IEEE Transactions on Medical Imaging, Vol. 24, 1323-1333, 2005
Liu Y, Gilormini P, Castañeda PP. Second-order homogenization estimates for texture evolution in polycrystalline halite. Tectonophysics, Vol. 406, 179-195, 2005
Liu Y and Castañeda PP. Homogenization estimates for the effective behavior and field heterogeneity in cubic and HCP polycrystals. Journal of the Mechanics and Physics of Solids, Vol. 52, 1175-1211, 2004