gallery

Stochastic reconstruction of sandstone microstructure from limited-angle x-ray tomography projections. Starting from a random initial configuration, the pixels are randomly selected and displaced to search the space of microstructures in order to find one that generates a simulated projection set that best matches the target set (insets at the lower right corner). Image courtesy @ Hechao Li, 2014. 

Dynamic reconstruction of lead-tin alloy using time-dependent correlation function. The coarsening process in lead-tin alloy is quantitatively characterized via a time-dependent correlation function which includes information on both the initial density fluctuations and a growing length scale. Dynamic reconstruction based-on surface optimization is utilized to evolve the microstructure and reconstruction the 4D coarsening process. Image courtesy @ Shaohua Chen, 2014. 

3D stochastic reconstruction of highly heterogeneous polycrystalline tin microstructure from single 2D micrograph. A multi-scale reconstruction process is developed to model and reconstruct highly heterogeneous polycrystalline microstructure based 2D EBSD micrographs alone. Smaller grains are first coarsened and reconstructed together with the large ones, which are resolved in a hieratical manner. Image courtesy @ Shaohua Chen, 2014. 

Simulated Ti-alloy microstructure from laser sintering. A hybrid finite-element cellular automaton technique is developed to simulate the microstructure evolution of Ti alloy during laser sintering. A variety of complex phase morphologies emerge from the simulation that mimics the actual microstructure obtained under the same processing conditions. The simulated structure will be subsequently analyzed to obtain mechanical properties. Image courtesy @ Shaohua Chen, 2015. 

Stress distribution in a Ti alloy with basket weaving structure. A novel volume-compensated lattice-particle simulation technique is developed to investigate mechanical properties, in particular fracture behavior of heterogeneous materials. Of particular interest is a high-cycle fatigue behavior of Ti-6Al-4V alloys obtained under different processing conditions. Image courtesy @ Yao Xu, 2015. 

Heterogeneous force chains in cellularized ECM. Our simulations have suggested that the fiberous nature of biopolymer network is able to support long-range force transmission through heterogeneous force chains. Such linear structures are formed by either fiber orientation during cell contraction or by pre-selection of linear structures consisting of aligned fibers. Image courtesy @ Long Liang, 2015. 

Microstructure evolution during solid state sintering. We have developed a novel kinetic Monte Carlo method that incorporates geometrical constraints on particle morphology evolution as well as sintering stress induced grain boundary migration and mass transfer to simulate morphology evolution and densification of a particle compact during free sintering. Image courtesy @ Shaohua Chen, 2016. 

Discharging hopper with mass-inflow boundary condition. We have enhanced the physical modeling capability of MFIX-DEM to alloy arbitrary particle size distribution. The animation shows the discharging process of the hopper with particle inflow through the top boundary and particle outflow at the bottom boundary. Two distinct solid phases (particles with distinct mean radius and physical properties) shown in different colors are used. Image courtesy @ Shaohua Chen, 2016. 

Electromigration in polycrystalline tin solder. The color map shows the diffusion paths of tin atoms from the cathode to anode from a hotspot due to current crowding effects caused by electromigration in polycrystalline tin solder obtained via kinetic Monte Carlo simulations. The tin diffusion will lead to the formation of a void close to the cathode. Image courtesy @ Deepak Karunakaran, 2016. 

Normal strain distribution in a disordered hyperuniform two-phase material. The color map shows themagnitude of the normal strain of the material under bi-axial tension loading. In this hyperuniform material, largescale volume fraction fluctuations are suppressed, leading to much more uniform distribution of the stress/strain. Such disordered hyperuniform materials possess superior mechanical properties such as higher fracture strength compared to their non-hyperuniform counterparts. Image courtesy @ Yaopengxiao Xu, 2017. 

Collective force generation in multi-cellular tumor diskoid. The color map shows the magnitude of the normal strain in the extracellular matrix due to contraction of the tumor cells in the diskoid. The color of the tumor cells (represented as circles) indicates the contraction phase. In this system, the contraction phases of individual tumor cells are spatially correlated with other cells with a correlation length of ~25 microns. Image courtesy @ Yaopengxiao Xu, 2017. 

Evolution of temperature field in a packed alloy powder bed during selective laser sintering. The color map shows the magnitude of the temperature in the packed powder bed, which is heated locally via a moving laser spot. The region in the center of the bed is being sintered and the powders in the sintering region will undergo complex phase transformation and microstructure evolution. Image courtesy @ Shaohua Chen, 2017. 

Microstructure evolution in Ti-6V-4Al alloy during selective laser sintering. The animation shows the nucleation and growth of alpha plates from a beta phase field during selective laser sintering. The growth direction and velocity depend on the local temperature and the crystal graphical orientation of the alpha planes depend on the parent beta grains. Image courtesy @ Shaohua Chen, 2017. 

Complex multiphase flow in a discharge hopper. The animation shows the discharge of four different solid phases with distinct particle sizes as a product of a chemical reaction from a hopper. The discharged particles are further collected by another container at the bottom of the hopper. From the discharge dynamics and the final packing configuration, the initial packing configuration in the hopper can be reconstruction, which reveals important information of the prior chemical reaction. Image courtesy @ Shaohua Chen, 2017. 

Distribution of shear stress on cell surface via modulus . The image shows the distribution of shear stress on a contracting cell, which is obtained by reconstructing the heterogeneous modulus of ECM surrounding the cell. Once the mechanical properties of ECM are obtained, the stresses on cell are obtained via finite element analysis. Image courtesy @ Shaohua Chen, 2017. 

Dynamical collision network in a non-equilibrium hard-sphere system. Two particles undergo a collision during a specific time interval are connected by a virtual bond, whose color indicates the "strength" of the dynamical connection between the two particles (i.e., the number of collisions). A hidden dynamic phase transition at low density regime has been identified using this analysis. Image courtesy @ Shaohua Chen, 2018. 

RVE of a heterogeneous adhesive composite-glass interface . The image shows the initial crack distribution on the interface, due to the expansion of the low-melting-point alloy phase in the composite (shown as blue), controlled by joule heating induced by electric current. One can use this mechanism to tune the dry adhesion force on the surface for soft gripper applications. Image courtesy @ Yaopengxiao Xu, 2018. 

Penetration of  force chains in highly heterogeneous ECM network. The image shows the propagation of force chains, generated by a migrating polarized cell, in a highly heterogeneous ECM, with distinct fiber orientations. It is suggested this range-long force transmission provides a promising mechanism for mechanical coupling of migrating cells. Image courtesy @ Hanqing Nan, 2018. 

Hyperuniform flow pattern resulted from hyperuniform distribution of particles . The image shows the flow flied resulted from a hyperuniform distribution of hard disks. It turns the resulting pattern is also hyperuniform, a exotic disordered state characterized by vanishing density fluctuations at large scales and hidden quasi-long-range order. Image courtesy @ Yu Zheng and Zhenya Ding, 2018. 

Unit cell of the superstructure for a metal-organic polyhedral cage. The image shows a unit cell of a face-centered cubic superstructure for a MO polyhedral cage, possessing the symmetry of a truncated cuboctahedron, on the thirteen Archimedean solids. Our simulations suggests that such MO particles can self-assemble into a double-helical nanowire structure on graphite substrate. Image courtesy @ Matthew Hart, 2018. 

Collective cancer cell invasion regulated by geometry dependent ECM collective remodeling. The imageshows a snapshot of invading cancer cells emanating from a triangle-shaped tumor organoid. The ECM (i.e., collagen network) surrounding the tumor is remodeled by the tumor to facilitate the invasion of the cells. Image courtesy @ Yu Zheng, 2019. 

Self-organization of active particles on random network. The image shows a snapshot of dynamic clusters formed by contractile active particles hopping from one node to another on a random network, following local durotaxis. For small particle density, small isolated clusters are form. Beyond a critical density, particles form a large dynamic cluster as shown here. Image courtesy @ Hanqing Nan, 2019. 

Dynamic heterogeneity in self-organizing clusters of active particles on network. The image shows the trajectories of randomly selected "radicals" in dynamic self-organizing cluster formed by these particles on random network, mimicking collective cell dynamics regulated by ECM-mediated force propogation. This behavior is similar to the dynamic heterogeneity in the vicinity of glass transition. Image courtesy @ Hanqing Nan, 2019. 

Active contractile particles on random network mimicking migrating cells in 3D Extracellular Matrix (ECM). Migrating cells in 3D can generate active pulling forces, which lead to a dynamically evolving force network in the system. We elucidate the role of such force network in regulating collective cell behaviors using an active-particle-on-network (APN) model, in which active particles can pull the fibers and hop between neighboring nodes of the network following local durotaxis. Our model reveals interesting collective cellular dynamics regulated by the force network. This image was selected as back cover for Soft Matter. Image courtesy @ Yang Jiao, 2019. 

Aggregation of active Brownian particles. Active Brownian particles possess an intrinsic persistent direction of motion, which is subject to diffusive rotation. ABP systems exhibit many interesting and novel collective behaviors such as aggregation at low densities, compared to the passive particle systems. By incorporating effective many-body interactions in the ABP systems, they can be employed to model collective dynamics of large-scale multi-cellular systems in complex micro-environment. Image courtesy @ Yu Zheng, 2019. 

Tumor geometry influences ECM remodeling. A start-shaped tumor diskoid composed of MDA-MB-231 breast cancer cells embedded in 3D collagen gel as ECM. The collagen fibers surrounding the tumor have been remodel to exhibit a clock-wise "flow" pattern. The image was selected as the cover for Mar. 2020 issue of Biophysical Journal. Image courtesy @ Prof. Bo Sun at Oregon State University, 2020. 

"Butterfly" displacement field resulted from two contractile cells. Two spherical cells generate isotropic pulling due to actin filament contraction and pull the local ECM fibers towards themselves. The ECM between the cells is cut using laser, leading to an opening crack. The cellular forces can be computed from the simulation. Image courtesy @ Yu Zheng, 2020. 

Evolution of stress distribution in a elastoplastic triangular-lattice network with a hexagonal hole under uniaxial loading via the Sweeping Process Theory (SPT). The simulation shown is based on a novel computational method based on SPT that "leapfrog" the long elastic branch of the system and directly jumps to the first yielding state of the network, which significantly improves the efficiency of the computation. More videos of SPT simulations can be found here.  Image courtesy @ Ivan Gudoshnikov, 2020. 

Self-assembly of supramolecular polyhedra into double-helical chain on graphene substrate.  The supramolecules possess a symmetry of truncated cuboctahedron (TCO), one of the 13 Archimedean solids,  with short-range attractions through the square facets.  Monte Carlo simulations reveal such TCO particles with "patchy" square facets can self-assemble under proper conditions into double-helical 1D structure, which is also realized experimentally.  Image courtesy @ Yang Jiao, 2021. 

Collective cell migration regulated by ECM-mediated active forces. The simulation shown is based on a generalized active particle model that explicitly incorporates the feedback interactions between active cells and mechanically remodeled ECM fibers, including the transmission and sensing of active tensile forces by ECM fibers. Feel free to try out our web-based interactive app simulating the cell-ECM system developed by Yu Zheng.  Image courtesy @ Yu Zheng, 2021. 

Disordered Hyperuniform 2D Network Containing a Significant Amount of the Stone-Wales Topological Defects. The schematic plot illustrates the structure factor associated with a disordered 2D network material generated by continuously introducing the Stone-Wales (SW) topological defects in a perfect honeycomb network, a model for many hexagonal 2D materials. The SW defects preserve the hyperuniformity property of the crystalline state of the materials, which is recently shown to lead to enhanced electronic transport.  Image courtesy @ Duyu Chen, Mohan Chen, Houlong Zhuang & Yang Jiao, 2021. 

2D Packing of Pentagonal Building Blocks with Global Three-Fold Rotational Symmetry. The packing models the self-assembly structure of pentagonal supramolecular building blocks with pi-pi type attractions through the corners. Remarkably, the packing structure exhibits emerging global 3-fold rotational symmetry from 5-fold symmetric shapes.  Image courtesy @ Yang Jiao, 2021. 

Mechanical Communication of Migrating Cells via Remodeled ECM Fiber Bundles. The migrating cells generate active pulling forces, which remodel the ECM network and form fiber bundles that transport mechanical signals, which in turn regulate the collective and correlated cell migration dynamics.  Image courtesy @ Qihu Fan, 2021. 

Topological Transformation Induced by Stone-Wales Defects Taking A Periodic Pentagonal Tiling to a Hexagon-Rhombus Tiling. The continuous spectrum of structures generated in this transformation pathway corresponds to a class of 2D materials AB2 possessing the remarkable property of hyperuniformity and unique electronic transport properties. These structures can be considered as the analog of "Barlow" packing variants with respect to the FCC and HCP packings.  Image courtesy @ Yu Zheng, 2021. 

Collective Aggregation of Invasive Tumor Cells Regulated by ECM-Mediated Mechanical Communications. The migrating tumor cells generate active pulling forces, which remodel the ECM network and form fiber bundles that transport mechanical signals, which in turn regulate the collective and correlated cell migration dynamics. This leads to abnormal aggregation of invasive tumor cells, rather than spreading out. Image courtesy @ Yu Zheng, 2022. 

Collective Remodeling of ECM by Active Cellular Forces. The migrating tumor cells generate active pulling forces, which remodel the ECM network and form fiber bundles that transport mechanical signals. The simulation shows the elastic remodeling of ECM where red color indicates higher fiber bundle density and stronger remodeling. Image courtesy @ Yu Zheng, 2022. 

Data-Driven Learning of Higher-Order Spatial Correlations As Microstructure Representations. Higher-order correlations provide a concise and explainable representation for complex material structures. We developed efficient data-driven method for learning minimal sets of high-order correlations that provide statistically accurate representations of complex materials. Image courtesy @ Sheng Cheng, 2022. 

Multihyperuniform High-Entropy Alloy. We recently discover a hidden quasi-long-range correlations in high entropy alloys, in which the large-scale composition fluctuations for all components are completely suppressed. This leads to a lower energy of the alloys and enhanced electronic band structures and low-temperature thermal transport properties. Image courtesy @ Duyu Chen, 2022. 

Collective Remodeling of ECM by Tumor Spheroid. Tumor spheroid during its development generate forces which actively remodel the surrounding ECM. The bulk tumor squeezes the surrounding ECM, while individual invasive cells degrade the fibers and generate fiber bundles as they migrate in the ECM. These remodeling results in highly heterogeneous and anisotropic micro-mechanical behaviors of the ECM materials, which have been recently quantified both experimental and via simulations.  Image courtesy @ Yang Jiao & Bo Sun 2022. 

Designer Anisotropic Hyperuniform Material with Directional Scattering Property. A realization of anisotropic binary composite possessing a lemniscate-shaped scattering pattern (lower left inset), obtained from stochastic optimization.  This material is stealthy hyperuniform (i.e., with complete suppression of infinite wavelength density fluctuations and scattering) along horizonal directions, and non-hyperuniform along vertical directions. Image courtesy @ Wenlong Shi 2023. 

Minimal Spheroid Packing Model for Complex Molecular Crystals. We establish a novel paradigm for modelling complex molecular crystals via an “inverse packing” framework, where molecular building blocks (BD) are represented by minimal anisotropic shapes. Instead of sticking to hard-particles with increasing shape complexity to model complex molecular BDs, we allow overlapping between the particles which is optimally determined using a “contact diagram” that we invented.  Image courtesy @ Weihao Wang & Shaodong Zhang 2023. 

3D Realization of an Antihyperuniform Two-Phase Medium. Using a Fourier-space construction method, we generate realizations of two-phase media with target spectral density (scattering properties). The image shows one with a spectral density that diverges at the origin, mimicking the huge fluctuations in systems at the critical point.  Image courtesy @ Yang Jiao 2024. 

Active Hyperuniform Phase of Magnetic Micro-Robots. Micro-robotic spinners with three-fold symmetric magnetic binding sites can self-assembly into a variety of active solid-state network structures, controlled by the rotation speed and magnetic binding strength.  An active hyperuniform phase can emerge for relative strong binding force and small rotation speed. Image courtesy @ Jing Wang 2024. 

Hyperuniform Organization in Leaf Vein Networks. Leaf vein network provides mechanical support and transport nutrients to leaf cells. We discover a universal hyperuniform organization in the leaf vein network, associated with the distribution of the areola, which gives an optimal transport behavior under the constraints of disorder. Image courtesy @ Yuan Liu 2024.