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Bulging and budding of lipid droplets from symmetric and asymmetric membranes: competition between membrane elastic energy and interfacial energy. (pdf, doi)
Soft Matter 17(21), 5319–5328 (2021). by M. Wang and X. Yi
Mechanics of cell interaction with intercellular nanoparticles: Shape-dependent competition between two-membrane trapping and single-membrane wrapping. (pdf, doi)
Extreme Mechanics Letters 46, 101296 (2021). by Z. M. Wu and X. Yi
Effects of processing parameters on the densification, microstructures and mechanical properties of pure tungsten fabricated by optimized selective laser melting: From single and multiple scan tracks to bulk parts. (pdf, doi)
International Journal of Refractory Metals and Hard Materials 96, 105490 (2021). by X. Ren et al.
Soft actuators based on liquid-vapor phase change composites. (pdf, doi)
Soft Robotics 8(3), (2021). by X. Y. Li et al.
Unified model for size-dependent to size-independent transition in yield strength of crystalline metallic materials. (pdf, doi)
Physical Review Letters 124(23), 235501 (2020). by W. B. Liu et al.
Structures and mechanical behaviors of soft nanotubes confining adhesive single or multiple elastic nanoparticles. (pdf, doi)
Journal of the Mechanics and Physics of Solids 137, 103867 (2020). by Z. M. Wu and X. Yi
Nanoparticle elasticity regulates phagocytosis and cancer cell uptake. (pdf, doi)
Science Advances 6(16), eaaz4316 (2020). by Y. Hui et al.
Nanomechanical characterization of pressurized elastic fluid nanovesicles using indentation analysis. (pdf, doi)
Extreme Mechanics Letters 34, 100613 (2020). by X. Y. Tang et al.
Finite indentation of pressurized elastic fluid nanovesicles by a rigid cylindrical indenter. (pdf, doi)
Acta Mechanica Solida Sinica 32(5), 633–642 (2019). by X. Y. Tang, J. X. Wang and X. Yi
Probabilistic and constitutive models for ductile-to-brittle transition in steels: A competition between cleavage and ductile fracture. (pdf, doi)
Journal of the Mechanics and Physics of Solids 135, 103809 (2020). by L. R. Chen et al.
A probabilistic model coupling with the temperature dependent constitutive relationship is proposed to describe the competition between the cleavage and ductile void failure of ferritic/martensitic steels with irradiation effects. At low temperature, the fracture toughness of ferritic/martensitic steels is relatively low as the cleavage is the main failure mechanism. At high temperature, the cleavage nucleation and crack propagation is suppressed, the ductile void growth gives rise to a relatively high fracture toughness. The underlying mechanism of the increase of the ductile-to-brittle transition temperature by irradiation (irradiation embrittlement) is that the irradiation defects induced hardening makes the flow stress increase greatly which can promote the development of cleavage micro-crack, and the irradiation-induced plasticity localization weakens the hindering effect from ductile void growth on the cleavage nucleation and propagation.
Curvature-mediated cooperative wrapping of multiple nanoparticles at the same and opposite membrane sides. (pdf, doi)
Nanoscale 11(42), 19751–19762 (2019). by Z. S. Yan et al.
Combining molecular dynamics simulations and theoretical analysis, we systematically investigate the cooperative effect in the wrapping of multiple adhesive nanoparticles at the same and opposite membrane sides. For nanoparticles binding to the same membrane side, the curvature-mediated interaction of nanoparticles could be either attractive or repulsive, depending on the initial particle distance and the competition between the membrane bending, particle binding and membrane protrusion. In contrast, the interaction between two nanoparticles binding to opposite membrane sides is always attractive and the cooperative wrapping is promoted. Our results enrich the fundamental understanding on high-order cooperative assemblies of nanoparticles or proteins in biological processes.
Force barrier for lipid sorting in the formation of membrane nanotubes. (pdf, doi)
Journal of Applied Mechanics 86(12), 121002 (2019). by X. Y. Tang, J. X. Wang and X. Yi
We perform a theoretical study on the formation of the multicomponent membrane nanotube and the associated curvature-driven lipid sorting and explore the dependence on the size of the pulling region. The presence of the lipid-disordered phase facilitates the nanotube formation by reducing the force barrier. Analytical solutions for the linear force-extraction relation and the membrane configurations in the early stage of the membrane extraction are obtained. At a small pulling region, the coupling between the membrane composition and mechanical properties play an important role in regulating the membrane extraction, and such an effect due to the phase separation diminishes gradually as the pulling region enlarges and the force barrier becomes dominated by a large pulling region.
Chain-length- and saturation-tuned mechanics of fluid nanovesicles direct tumor delivery. (pdf, doi)
ACS Nano 13(7), 7676–7689 (2019). by Z. Dai et al.
By changing the lipid chain length and saturation, liposomes of different rigidities are obtained. It is found that stiff liposomes hardly deformed and soft liposomes changed their shape irregularly, both slowing their MCS penetration. Liposomes with intermediate rigidity exhibit better tumor extracellular matrix diffusion and multicellular spheroid (MCS) penetration and retention than that of their stiffer or softer counterparts, contributing to improved tumor suppression. Our results suggest that liposome mechanics could be a design parameter for enhancing drug delivery.
Role of nanoparticle mechanical properties in cancer drug delivery. (pdf, doi)
ACS Nano 13(7), 7410–7424 (2019). by Y. Hui et al.
This review article provides an overview of the impacts of nanoparticle mechanical properties on cancer drug delivery, including (1) basic terminologies of the mechanical properties of nanoparticles and techniques for characterizing these properties; (2) current methods for fabricating nanoparticles with tunable mechanical properties; (3) in vitro and in vivo studies that highlight key biological performances of stiff and soft nanoparticles, including blood circulation, tumor or tissue targeting, tumor penetration, and cancer cell internalization, with a special emphasis on the underlying mechanisms that control those complicated nano-bio interactions at the cellular, tissue, and organ levels.
Why are nanoparticles trapped at cell junctions when the cell density is high? (pdf, doi)
Nanoscale 11(14), 6602–6609 (2019). by T. T. Yue et al.
Our experimental and computational studies show that nanoparticles simultaneously encountering two adjacent cells as regularly observed in tissues could be trapped at cell junctions with impeded cell uptake. The stable distribution of nanoparticles outside of cells at a high cell density is regulated by the adhesion, bending and protrusion of membranes from these cells.
Temperature- and rigidity-mediated rapid transport of lipid nanovesicles in hydrogels. (pdf, doi)
Proc. Natl. Acad. Sci. U. S. A. 116(12), 5362–5369 (2019). by M. R. Yu et al.
It is found that the liposomes gain optimal diffusivity when their phase transition temperature is around the ambient temperature, which signals a drastic change in the nanovesicle rigidity. Liposomes with phase transition temperature around body temperature exhibit enhanced cellular uptake in mucus-secreting epithelium and show significant improvement in oral insulin delivery efficacy in diabetic rats.
Model of nanoindentation size effect incorporating the role of elastic deformation. (pdf, doi)
J. Mech. Phys. Solids 126, 245–255 (2019). by W. B. Liu et al.
A theoretical model incorporating the role of elastic deformation is proposed for modeling the indentation size effect. It is shown that, while elastic deformation is generally not associated with the generation of geometrically necessary dislocations, neglecting it can lead to severe overestimation of both the nanoindentation hardness, particularly below 100 nm. Our model predictions are in good agreement with experimental results on nanoindentation of single Cu and MgO crystals. A similar scheme is applied for ion-irradiated metallic materials.
Sidewall contact regulating the nanorod packing inside vesicles with relative volumes. (pdf, doi)
Soft Matter 15(12), 2552–2559 (2019). by Z. M. Wu et al.
Theoretical analysis is performed to investigate the interplay between the lipid vesicle and encapsulated rigid nanorods of finite diameters and selected geometries. The contact between the vesicle protrusion and the rod sidewall, neglected in most theoretical studies, is shown to play an important role in regulating the vesicle tubulation, membrane tension, and axial contact force on the nanorod. Depending on the rod size and the relative vesicle volume, the confining vesicle evolves from a prolate into different shapes. Corresponding morphological phase diagrams are determined. Moreover, it is shown that there exists an optimal filament number at which the encapsulated weakly cross-linked filament bundle maintains the largest length in a mechanically stable state.
Mechanics of the formation, interaction and evolution of membrane tubular structures. (pdf, doi)
Biophys. J. 116(5), 884–892 (2019). by S. X. Li et al.
MD simulations and theoretical modeling are presented to reveal the physics of the formation and interaction of membrane protrusions pulled from a lipid membrane. Depending on the pulling displacement and separation distance, different membrane configurations, including an individual tubular protrusion, V-shaped nanotubes, a Y-shaped tube configuration through coalescence, and two weakly interacting tubular protrusions, are observed. We analyze lipid flow accompanying the membrane shape transition and theoretically estimate the corresponding energy profiles.
Membrane wrapping efficiency of elastic nanoparticles during endocytosis: Size and shape matter. (pdf, doi)
ACS Nano 13(1), 215–228 (2019). by Z. Q. Shen et al.
The receptor-mediated endocytosis of elastic nanoparticles with different sizes and shapes, including sphere-like, oblate-like, and prolate-like, is systematically investigated through MD simulations. It is revealed that the wrapping efficiency is a result of competition between the receptor diffusion kinetics and thermodynamic driving force associated with system energy variation. Under the volume constraint of particles, the softer spherical nanoparticles are less efficiently be fully wrapped due to their elastic deformation. Moreover, the difference in wrapping efficiency between soft and rigid spherical particles increases with their sizes. The oblate ellipsoid is found to be the least sensitive geometry to the variation in particle elasticity among the spherical, prolate, and oblate shapes during the membrane wrapping.
Multimaterial microfluidic 3D printing of textured composites with liquid inclusions. (pdf, doi)
Adv. Sci. 6(3), 1800730 (2019). by X. Y. Li et al.
By combining the direct ink writing and microfluidics, a novel multimaterial microfluidic 3D printing system is built for fabricating textured composites with liquid inclusions of programmable spatial distribution and compositions. We demonstrate the versatility of our multimaterial 3D printing framework in fabricating 1D, 2D, and 3D structures and functional composite systems such as layered composite beams of tunable thermal property and self-healing materials.
Mechanics of cellular packing of nanorods with finite and non-uniform diameters. (pdf, doi)
Nanoscale 10, 14090 (2018). by X. Yi, G. J. Zou and H. J. Gao
Theoretical modeling and MD simulations demonstrate that the diameter, length, and shape of an encapsulated nanorod together play key roles in regulating its mechanical interplay with the confining vesicle, shedding light on the cellular packing of microtubule bundles, filopodial protrusion, mitotic cell division, and cytotoxicity.
Packing of flexible 2D materials in vesicles. (pdf, doi)
J. Phys. D: Appl. Phys. 51, 224001 (2018). by G. J. Zou et al.
Molecular dynamics simulations and theoretical analysis are performed to investigate the packing of a flexible 2D sheet in a vesicle confinement. Depending on the size and bending rigidity ratios between the confined sheet and the vesicle membrane, a variety of packing morphologies are observed, including a conical shape, a shape of three-fold symmetry, a cylindrically curved shape, and an axisymmetrically buckled shape. Packing phase diagrams are constructed based on buckling analyses.
A minimal mechanics model for mechanosensing of substrate rigidity gradient in durotaxis. (pdf, doi)
Biomech. Model. Mechanobiol. (2018). by B. Marzban, X. Yi and H. Y. Yuan
A simple elasticity mechanics model is established to predict durotaxis in single cell durotaxis, the directed cell migration toward mechanically stiffer regions. With consideration of the elasticity effects of the cytoskeleton, focal adhesion, and extracellular matrix, we show that the static cell equilibrium alone is sufficient to account for the generation of the larger focal adhesion force on the stiffer region of the ECM substrate, which subsequently leads to the durotaxis. A finite element model is developed and predicts the durotaxis observed in experiments.
Size-dependent formation of membrane nanotubes: continuum modeling and molecular dynamics simulations. (pdf, doi)
Phys. Chem. Chem. Phys. 20, 3474 (2018). by F. L. Tian et al.
Theoretical analysis and dissipative particle dynamics (DPD) simulations are performed to investigate the lipid membrane nanotube formation. As the size of the pulling region and the membrane tension increases, the force-extraction curve becomes discontinuous and the membrane undergoes a discontinuous shape transition. A formula characterizing the nonlinear relationship between the maximum static pulling force and the size of pulling region is identified. DPD simulations indicate that the steady state force is linearly proportional to the pulling velocity and the pulling region size.
Packing of flexible nanofibers in vesicles. (pdf, doi)
Extreme Mech. Lett. 19, 20 (2018). by G. J. Zou et al.
Packing of a flexible nanofiber inside an elastic vesicle depends on not only the geometrical and material properties of the encapsulated nanofiber but also its initial configuration in the vesicle confinement. Based on the vesicle morphology, three distinct types of morphological packing phases (lemon, dumpling, and cherry) are found from MD simulations. Packing phase diagrams with respect to the normalized nanofiber length and bending stiffness are determined, consistent with experimental observation. The effect of osmotic pressure on the nanofiber packing is also analyzed.
Kinetics of receptor-mediated endocytosis of elastic nanoparticles. (pdf, doi)
Nanoscale 9, 454 (2017). by X. Yi and H. J. Gao
The membrane wrapping of soft nanoparticles is kinetically faster than that of stiff ones. Further calculations indicated that membrane tension plays an important role in the control of minimum particle radius but has a negligible effect on the wrapping rate. The role of the stochastic receptor-ligand binding in the endocytosis has also been investigated.
Incorporation of soft particles into lipid vesicles: Effects of particle size and elasticity. (pdf, doi)
Langmuir 32, 13252 (2016). by X. Yi and H. J. Gao
Budding of an adhesive elastic particle out of a lipid vesicle. (pdf, doi)
ACS Biomater. Sci. Eng. 3, 2954 (2017). by X. Yi and H. J. Gao
Theoretical studies indicate that the incorporation of small particles involves smooth shape evolution, while the vesicle wrapping of large particles exhibits a discontinuous shape transition. In the case of outward budding, a discontinuous vesicle shape transformation can occur for a vesicle with positive spontaneous curvature but not for a vesicle with zero or negative spontaneous curvature. Moreover, larger adhesion energy is required for soft particles to reach the state of full release than full wrapping. This result suggests that tuning the cell membrane affinity might help to keep internalized soft drug agents stay in the cell, instead of being released out through exocytosis.
Nanomechanical mechanism for lipid bilayer damage induced by carbon nanotubes confined in intracellular vesicles. (pdf, doi)
Proc. Natl. Acad. Sci. U. S. A. 113, 12374 (2016). by W. P. Zhu et al.
Stiff nanotubes beyond a critical length are compressed by lysosomal membranes causing persistent tip contact with the inner membrane leaflet, leading to lipid extraction, lysosomal permeabilization, release of cathepsin B into the cytoplasm, and cell death. The fundamental mechanistic link between nanotube stiffness and cytotoxicity is revealed.
Biological and environmental interactions of emerging two-dimensional nanomaterials. (pdf, doi)
Chem. Soc. Rev. 45, 1750 (2016). by Z. Y. Wang et al.
The review proposes a framework for more systematic investigation of biological behavior rooted in fundamental materials chemistry and physics. That framework considers three fundamental interaction modes: (i) chemical interactions and phase transformations, (ii) electronic and surface redox interactions, and (iii) physical and mechanical interactions that are unique to near-atomically-thin, high-aspect-ratio solids.
Cell interaction with graphene microsheets: Near-orthogonal cutting versus parallel attachment. (pdf, doi)
Nanoscale 7, 5457 (2015). by X. Yi and H. J. Gao
Graphene microsheets can either undergo a near-orthogonal cutting or a parallel attachment mode of interaction with cell membranes. Driven by the membrane splay and tension energies, a two-dimensional microsheet would adopt a near-perpendicular configuration with respect to the membrane in the transmembrane penetration mode, whereas the membrane bending and tension energies would lead to parallel attachment.
Phase diagrams and morphological evolution in wrapping of rod-shaped elastic nanoparticles by cell membrane: A two-dimensional study. (pdf, doi)
Phys. Rev. E 89, 062712 (2014). by X. Yi and H. J. Gao
A theoretical analysis is performed to investigate phase diagrams and morphological evolution of an elastic rod-shaped nanoparticle wrapped by a lipid membrane in two dimensions. While symmetric morphologies are observed in the early and late stages of wrapping, in between a soft rod-shaped nanoparticle undergoes a dramatic symmetry breaking morphological change while stiff and rigid nanoparticles experience a sharp reorientation.
A universal law for cell uptake of one-dimensional nanomaterials. (pdf, doi)
Nano Lett. 14, 1049 (2014). by X. Yi, X. H. Shi and H. J. Gao
Cell uptake of one-dimensional (1D) nanomaterials follows a near-perpendicular entry mode at small membrane tension but it switches to a near-parallel interaction mode at large membrane tension. This membrane tension-dependent behavior has been observed in the interplay between cell membranes and 1D nanomaterials such as carbon nanotubes, filopodia, microtubules, and particle chains.
Cellular uptake of elastic nanoparticles. (pdf, doi)
Phys. Rev. Lett. 107, 098101 (2011). by X. Yi, X. H. Shi and H. J. Gao
Cell membrane wrapping of a spherical thin elastic shell. (pdf, doi)
Soft Matter 11, 1107 (2015). by X. Yi and H. J. Gao
Theoretical analysis is performed to study cell uptake of elastic nanoparticles such as liposomes and polymer capsules. It is found that stiffer particles can achieve full wrapping more easily than softer particles, while softer particles experience smaller energy changes during wrapping and might be more favorable in case full wrapping is not necessary. Our results provide feasible explanations why viral particles harden right before budding and then soften again in the uptake stage. Moreover, our analysis suggest that precise control of the particle elasticity can be another appealing way to control cell uptake.
Water-swelling-induced morphological instability of a supported polymethyl methacrylate thin film. (pdf, doi)
Langmuir 26, 7651 (2010). by B. X. Jing et al.
Poly(methyl methacrylate) (PMMA) thin films in water partially detach from the solid substrate, resulting in the formation of bubbles under water. The process is reversible. Theoretical analysis based on a two-layer model (swollen layer and interior layer) shows that the partial swelling of PMMA in water is the physical origin of bubble formation.
Surface stress induced by interactions of adsorbates and its effect on deformation and frequency of microcantilever sensors. (pdf, doi)
J. Mech. Phys. Solids 57, 1254 (2009). by X. Yi and H. L. Duan
Vibration of cantilevers with rough surfaces. (pdf, doi)
Acta Mechanica Solida Sinica 22, 550 (2009). by H. L. Duan, Y. H. Xue and X. Yi
We establish the relations between the adsorption-induced surface stress and the van der Waals and Coulomb interactions in terms of the physical and chemical interactions between adsorbates and solid surfaces. Based on the relations, we present a theoretical framework to predict the deflection and resonance frequencies of microcantilevers with the simultaneous effects of the eigenstrain, surface stress and adsorption mass. Further analysis indicates that surface roughness of the microcantilevers can enhance, decrease or even annul the effect of surface stress on the resonance frequency.
Prediction of complex dielectric constants of polymer-clay nanocomposites. (pdf, doi)
Phys. Lett. A 372, 68 (2007). by X. Yi et al.
Theoretical analysis indicates that the morphology of the clay fillers and the thickness and dielectric properties of the interphases play an important role in determining the dielectric properties of polymer-clay nanocomposites.
A unified scheme for prediction of effective moduli of multiphase composites with interface effects.
Part I: Theoretical framework. (pdf, doi)
Mech. Mater. 39, 81 (2007). by H. L. Duan et al.
Part II—Application and scaling laws. (pdf, doi)
Mech. Mater. 39, 94 (2007). by H. L. Duan et al.
In the two-part papers, a unified theoretical framework based on a replacement procedure and the generalized self-consistent method (GSCM) is established to predict the effective moduli of multiphase composites containing spherical particles or cylindrical fibers with various interface effects. The analytical solutions for the effective moduli and numerical companion with experimental results are presented.
Solutions of inhomogeneity problems with graded shells and application to core-shell nanoparticles and composites. (pdf, doi)
J. Mech. Phys. Solids 54(7), 1401 (2006). by H. L. Duan et al.
Eshelby equivalent inclusion method for composites with interface effects. (pdf, doi)
Key Eng. Mater. 312, 161 (2006). by H. L. Duan et al.
Eshelby formalism for multi-shell nano-inhomogeneities. (pdf, doi)
Arch. Mech. 59, 259 (2007). by X. Yi et al.
The Eshelby tensors and stress concentration tensors are derived for a spherical inhomogeneity with a graded shell embedded in an alien infinite matrix. The solution is then specialized to inhomogeneous inclusions in finite spherical domains with fixed displacement or traction-free boundary conditions. Moreover, the strain distributions in core-shell nanoparticles with eigenstrains induced by lattice mismatches are calculated using the Eshelby tensors in the finite domains. Within the framework of the equivalent inclusion method, the Eshelby and stress concentration tensors in the three-phase configuration are used to formulate the generalized self-consistent prediction of the effective moduli of composites containing spherical particles.
Conductivities of heterogeneous media with graded anisotropic constituents. (pdf, doi)
J. Appl. Phys. 100, 034906 (2006). by H. L. Duan et al.
Effective conductivities of heterogeneous media containing multiple inclusions with various spatial distributions. (pdf, doi)
Phys. Rev. B 73, 174203 (2006). by H. L. Duan et al.
Bounds on effective conductivities of heterogeneous media with graded constituents. (pdf, doi)
Phys. Rev. B 73, 104208 (2006). by J. X. Wang, H. L. Duan and X. Yi
The effective conductivities of heterogeneous media containing discretely suspended particles with a graded interphase or graded particles are obtained based on an energy equivalency condition. The corresponding upper and lower bounds of the effective conductivities are also derived. For heterogeneous media containing ellipsoidal inclusions of diverse shapes, spatial distributions, and orientations, another scheme is proposed to predict the effective conductivities.
Strain distributions in nano-onions with uniform and non-uniform compositions. (pdf, doi)
Nanotechnology 17, 3380 (2006). by H. L. Duan et al.
Compatible composition profiles and critical sizes of alloyed quantum dots. (pdf, doi)
Phys. Rev. B 74, 195328 (2006). by H. L. Duan et al.
The strains in embedded and free-standing nano-onions with uniform and non-uniform compositions are investigated. It is found that the strains in the nano-onions can be modified by adjusting their compositions and structures.