Current Research and Scholarly Interests
Classification for the flow defects in metallic glass materials;
Molecular Dynamics Simulation for the Nano-indentation of Al-Mg alloy;
Spherical Harmonics Approach of the spherical elasticity problem;
- Phagocytic 'teeth' and myosin-II 'jaw' power target constriction during phagocytosis ELIFE 2021; 10
Phagocytic 'teeth' and myosin-II 'jaw' power target constriction during phagocytosis.
Phagocytosis requires rapid actin reorganization and spatially controlled force generation to ingest targets ranging from pathogens to apoptotic cells. How actomyosin activity directs membrane extensions to engulf such diverse targets remains unclear. Here, we combine lattice light-sheet microscopy (LLSM) with microparticle traction force microscopy (MP-TFM) to quantify actin dynamics and subcellular forces during macrophage phagocytosis. We show that spatially localized forces leading to target constriction are prominent during phagocytosis of antibody-opsonized targets. This constriction is largely driven by Arp2/3-mediated assembly of discrete actin protrusions containing myosin 1e and 1f ('teeth') that appear to be interconnected in a ring-like organization. Contractile myosin-II activity contributes to late-stage phagocytic force generation and progression, supporting a specific role in phagocytic cup closure. Observations of partial target eating attempts and sudden target release via a popping mechanism suggest that constriction may be critical for resolving complex in vivo target encounters. Overall, our findings present a phagocytic cup-shaping mechanism that is distinct from cytoskeletal remodeling in 2D cell motility and may contribute to mechanosensing and phagocytic plasticity.
View details for DOI 10.7554/eLife.68627
View details for PubMedID 34708690
- Stress effects on the energy barrier and mechanisms of cross-slip in FCC nickel JOURNAL OF THE MECHANICS AND PHYSICS OF SOLIDS 2020; 144
Microparticle traction force microscopy reveals subcellular force exertion patterns in immune cell-target interactions.
2020; 11 (1): 20
Force exertion is an integral part of cellular behavior. Traction force microscopy (TFM) has been instrumental for studying such forces, providing spatial force measurements at subcellular resolution. However, the applications of classical TFM are restricted by the typical planar geometry. Here, we develop a particle-based force sensing strategy for studying cellular interactions. We establish a straightforward batch approach for synthesizing uniform, deformable and tuneable hydrogel particles, which can also be easily derivatized. The 3D shape of such particles can be resolved with superresolution (<50 nm) accuracy using conventional confocal microscopy. We introduce a reference-free computational method allowing inference of traction forces with high sensitivity directly from the particle shape. We illustrate the potential of this approach by revealing subcellular force patterns throughout phagocytic engulfment and force dynamics in the cytotoxic T-cell immunological synapse. This strategy can readily be adapted for studying cellular forces in a wide range of applications.
View details for DOI 10.1038/s41467-019-13804-z
View details for PubMedID 31911639
- Spherical harmonics method for computing the image stress due to a spherical void JOURNAL OF THE MECHANICS AND PHYSICS OF SOLIDS 2019; 126: 151–67
Strengthening Mechanism of a Single Precipitate in a Metallic Nanocube
2019; 19 (1): 255–60
Nano-precipitates play a significant role in the strength, ductility and damage tolerance of metallic alloys through their interaction with crystalline defects, especially dislocations. However, the difficulty of observing the action of individual precipitates during plastic deformation has made it challenging to conclusively determine the mechanisms of the precipitate-defect interaction for a given alloy system, and presents a major bottleneck in the rational design of nanostructured alloys. Here we demonstrate the in situ compression of core-shell nanocubes as a promising platform to determine the precise role of individual precipitates. Each nanocube with a dimension of ~85 nm contains a single spherical precipitate of ~25 nm diameter. The Au-core/Ag-shell nanocubes show a yield strength of 495 MPa with no strain hardening. The deformation mechanism is determined to be surface nucleation of dislocations which easily traverses through the coherent Au-Ag interface. On the other hand, the Au-core/Cu-shell nanocubes show a yield strength of 829 MPa with a pronounced strain hardening rate. Molecular dynamics and dislocation dynamics simulations, in conjunction with TEM analysis, have demonstrated the yield mechanism to be the motion of threading dislocations extending from the semi-coherent Au-Cu interface to the surface, and strain hardening to be caused by a single-armed Orowan looping mechanism. Nanocube compression offers an exciting opportunity to directly compare computational models of defect dynamics with in situ deformation measurements to elucidate the precise mechanisms of precipitate hardening.
View details for DOI 10.1021/acs.nanolett.8b03857
View details for Web of Science ID 000455561300032
View details for PubMedID 30525680