Characterization and control of the mechanical properties of the extracellular matrix are critical to the interpretation of results of in vitro studies of cultured tissues and cells and for the design of functional engineered constructs. In this work a viscoelastic tensile test system and custom culture chambers were developed and characterized. The system allowed quantification of strain as we...

Recent developments on the optimization and parameter estimation in hybrid active-passive composite sandwich structures are presented. For this purpose, a mixed layerwise finite element model has been formulated, by considering a higher order shear deformation theory to represent the displacement field in the viscoelastic core and a first order theory for the displacement fields of the adjacent...

The present work reports a discrete stress-dependent, complex compliance spectra method that may be used to predict the mechanical response of nonlinear viscoelastic polymers during creep and recovery processes. The method is based on the observation that the real and imaginary parts of a discrete complex compliance frequency spectra obtained from creep and recovery measurements are smooth, eas...

We present a method to improve accuracy in measurements of nanoscale viscoelastic material properties with contact resonance atomic force microscope methods. Through the use of the two-dimensional hydrodynamic function, we obtain a more precise estimate of the fluid damping experienced by the cantilever-sample system in contact resonance experiments, leading to more accurate values for the tip-...

The aim of this paper is to introduce a new three-dimensional elastoviscoplastic model that combines both the Oldroyd viscoelastic model and the Herschel-Bulkley viscoplastic model with a power-law index n > 0. The present model is derived to satisfy the second law of thermodynamics. Various fluids of practical interest, such as liquid foams, droplet emulsions or blood, present such elastovisco...

A numerical algorithm is presented that simulates large deformations of heterogeneous, viscoelastic materials in two dimensions. The algorithm is based on a spectral/finite difference method and uses the Eulerian formulation including objective derivatives of the stress tensor in the rheological equations. The viscoelastic rheology is described by the linear Maxwell model, which consists of an ...

The paper is devoted to homogenization of two-phase incompressible viscoelastic flows with disordered microstructure. We study two cases. In the first case, both phases are modeled as Kelvin-Voight viscoelastic materials. In the second case, one phase is a Kelvin-Voight material, and the other is a viscous Newtonian fluid. The microscale system contains the conservation of mass and balance of m...

We present the first quantitative measurement of the receding contact angle between a soft viscoelastic material and a solid surface during the debonding of the material. We developed a new method of observation, based on the technique pioneered by Yamaguchi et al. (T. Yamaguchi, K. Koike, and M. Doi, Euro. Phys. Lett., 2007, 77, 64002). In a probe-tack geometry, we obtained a 3D-like view of t...

Low pulling forces applied locally to cell surface membranes produce viscoelastic cell surface protrusions. As the force increases, the membrane can locally separate from the cytoskeleton and a tether forms. Tethers can grow to great lengths exceeding the cell diameter. The protrusion-to-tether transition is known as the crossover. Here we propose a unified approach to protrusions and tethers p...

OF THE DISSERTATION The Material Point Method for the Physics-Based Simulation of Solids and Fluids by Chenfanfu Jiang Doctor of Philosophy in Computer Science University of California, Los Angeles, 2015 Professor Demetri Terzopoulos, Co-chair Professor Joseph M. Teran, Co-chair Simulating fluids and solid materials undergoing large deformation remains an important and challenging problem in Co...