A5026962319- Micro and Nano Robotics
- Nonlinear Dynamics and Pattern Formation
- Adhesion, Friction, and Surface Interactions
- Advanced Materials and Mechanics
- High-Velocity Impact and Material Behavior
- Mechanical Behavior of Composites
- Advanced Thermodynamics and Statistical Mechanics
- Force Microscopy Techniques and Applications
- Material Dynamics and Properties
- Modular Robots and Swarm Intelligence
- Fluid Dynamics and Turbulent Flows
- Characterization and Applications of Magnetic Nanoparticles
- Image Processing and 3D Reconstruction
- Rock Mechanics and Modeling
- Solar and Space Plasma Dynamics
- Hydraulic Fracturing and Reservoir Analysis
- Control and Dynamics of Mobile Robots
- Oceanographic and Atmospheric Processes
- Microfluidic and Bio-sensing Technologies
- Seismology and Earthquake Studies
- High-pressure geophysics and materials
- Thermodynamic properties of mixtures
- Particle Dynamics in Fluid Flows
- Pickering emulsions and particle stabilization
- Mechanical and Optical Resonators
Georgia Institute of Technology
2024
University of California System
2024
University of California, Santa Barbara
2018-2022
Hebrew University of Jerusalem
2009-2018
Watching defects flow and grow Orientational topological in liquid crystals, known as disclinations, have been visualized polymeric materials or through mesoscale simulations of the local orientation molecules. Duclos et al. report experimental visualization structure dynamics disclination loops active, three-dimensional nematics using light-sheet microscopy to watch motion nematic molecules driven by microtubule bundles (see Perspective Bartolo). This setup makes it possible directly...
Controlling interfaces of phase-separating fluid mixtures is key to the creation diverse functional soft materials. Traditionally, this accomplished with surface-modifying chemical agents. Using experiment and theory, we studied how mechanical activity shapes that separate an active a passive fluid. Chaotic flows in give rise giant interfacial fluctuations noninertial propagating waves. At high activities, stresses disrupt interface continuity drive droplet generation, producing...
We study the structure and dynamics of interface separating a passive fluid from microtubule-based active fluid. Turbulent-like flows power giant interfacial fluctuations, which exhibit pronounced asymmetry between regions positive negative curvature. Experiments, numerical simulations, theoretical arguments reveal how breaks up spatial symmetry fundamental bend instability to generate local vortical that lead asymmetric fluctuations. The magnitude deformations increases with activity: In...
Fracture of highly stretched materials challenges our view how things break. We directly visualize rupture tough double-network gels at >50% strain. During fracture, crack tip shapes obey a x∼y^{1.6} power law, in contrast to the parabolic profile observed low-strain cracks. A new length scale ℓ emerges from law; we show that scales with stored elastic energy and diverges when velocity approaches shear wave speed. Our results undergo brittle fracture provide testing ground for large-strain mechanics.
When fast cracks become unstable to microscopic branching (microbranching), fracture no longer occurs in an effective 2D medium. We follow in-plane crack front dynamics via real-time measurements brittle gels as microbranching unfolds and progresses. first show that spatially local energy balance quantitatively describes dynamics, even when translational invariance is badly broken. Furthermore, our results explain microbranch dynamics; why microbranches form along localized chains how...
The interface of an active liquid crystal can support travelling waves. We derive dispersion relations from a linear theory and compute the dynamical structure factor continuum simulations.
We study the transition from fluid at rest to turbulence in a rotating tank. The energy is transported by inertial wave packets through volume. These high amplitude waves propagate velocities consistent with those calculated linearized theory [H. P. Greenspan, (Cambridge University Press, Cambridge, England, 1968)]. A "front" temporal evolution of power spectrum indicates time scale for transport linear speed. Nonlinear transfer between modes governed different, longer, scale. observed...
Cracks in brittle materials produce two types of generic surface structures: facets at low velocities and microbranches higher ones. Here we observe a transition from faceting to microbranching polyacrylamide gels that is characterized by nonlinear dynamic localization crack fronts. To better understand this process derive first-principles equation motion for fronts the context scalar elasticity. Its solution shows focusing coupled rate dependence dissipation governs microbranching.
Are heterogeneous materials harder to break than homogeneous ones? Predicting rapid crack propagation in the presence of inhomogeneities remains a challenge. Linear perturbations leave net speed fracture unchanged. We obtain nonlinear equation motion for planar fronts gain insight into dynamic moderately solids. The coupling front geometry heterogeneity landscape renormalizes energy dissipation and velocity. In whose toughness is weakly sensitive speed, such as silica glass, results...
We study the structure and dynamics of interface separating a passive fluid from microtubule-based active fluid. Turbulent-like flows power giant interfacial fluctuations, which exhibit pronounced asymmetry between regions positive negative curvature. Experiments, numerical simulations, theoretical arguments reveal how breaks up spatial symmetry fundamental bend instability to generate local vortical that lead asymmetric fluctuations. The magnitude deformations increases with activity: In...
A wide range of glassy and disordered materials exhibit complex, non-exponential, structural relaxation (aging). We propose a simple nonlinear rate equation d\delta/dt = [1-exp (b\delta)], where '\delta' is the normalized deviation macroscopic variable from its equilibrium value, to describe relaxation. Analysis extensive experimental data shows that this quantitatively captures relaxation, 'a' 'b' are both temperature-, more importantly, history-dependent parameters. This analysis...
We show that, in dimension higher than one, heat diffusion and viscosity cannot arrest thermal collapse a freely evolving dilute granular gas, even the absence of gravity. Thermal involves finite-time blowup gas density. It was predicted earlier ideal, Euler hydrodynamics gases gravity, nonideal, Navier-Stokes presence determine, analytically numerically, dynamic scaling laws that characterize flow close to collapse. also investigate bifurcations circular wedge-shaped containers. Our results...
The interaction of crack fronts with asperities is central to the criteria fracture in heterogeneous materials and for prediction surface formation. It known how dynamic respond small, 1st-order, perturbations. Large localized disturbances motion, however, induce geometric nonlinear effects that are beyond existing linear theories. Because determination 3D elastic fields surrounding perturbed a necessary step towards any theoretical study front dynamics, we develop 2nd-order perturbation...
The interaction of crack fronts with asperities is central to the criteria fracture in heterogeneous materials and for prediction surface formation. It known how dynamic respond small, 1st-order, perturbations. Large localized disturbances motion, however, induce geometric nonlinear effects that are beyond existing linear theories. Because determination 3D elastic fields surrounding perturbed a necessary step towards any theoretical study front dynamics, we develop 2nd-order perturbation...
Active liquid crystals exert nonequilibrium stresses on their surroundings through constant consumption of energy, giving rise to dynamical steady states not present in equilibrium. The paradigmatic example an active crystal is a suspension microtubule bundles powered by kinesin motor proteins, which exhibits self-sustained spatiotemporal chaotic flows. This system has been modelled using continuum theories that couple the orientation Recently focus shifted interfacial properties mixtures...
We use the chaotic flows generated by a microtubule-based active fluid to assemble self-binding actin filaments into thin elastic sheets. Starting from uniformly dispersed state, drive motion of filaments, inducing their bundling and formation bundle-bundle connections that ultimately generate an network. The emerging network separates form sheets suspended at sample midplane. At intermediate times, drives large in-plane out-of-plane deformations sheet which are driven low-energy bending...
Using scanning transmission electron microscopy, researchers watch a