The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Xi-qiao Feng - One of the best experts on this subject based on the ideXlab platform.
-
Surface wrinkling of anisotropic films bonded on a Compliant Substrate
International Journal of Solids and Structures, 2018Co-Authors: Si-fan Yin, Yanping Cao, Xi-qiao FengAbstract:Abstract Material anisotropy regulates the instabilities of film–Substrate systems at different length scale. In this paper, we investigate the surface wrinkling and morphological evolution of an orthotropic thin film resting on a Compliant Substrate. Under different loading conditions, the system may buckle into various surface patterns, e.g., stripe, checkerboard, and herringbone, which are analyzed by using the Foppl–von Karman plate theory. The Fourier spectral method is employed to simulate the morphological evolutions of surface patterns under different loading biaxialities. We find that both loading biaxiality and material anisotropy affect the characteristics of surface wrinkling patterns and their evolutions. Stripe and checkerboard modes often emerge at the critical buckling and they tend to transform into herringbone and labyrinth patterns during postbuckling. Phase diagrams are established to reveal the dependence of surface patterns on material anisotropy, Poisson's effect, and loading biaxiality. This study may help design diverse functional surfaces and deepen our understanding of the morphogenesis of some soft biological tissues and organs.
-
effects of tension compression asymmetry on the surface wrinkling of film Substrate systems
Journal of The Mechanics and Physics of Solids, 2016Co-Authors: Xiao Huang, Wei Hong, Yanping Cao, Xi-qiao FengAbstract:Abstract Many soft materials and biological tissues are featured with the tension–compression asymmetry of constitutive relations. The surface wrinkling of a stiff thin film lying on a Compliant Substrate is investigated through theoretical analysis and numerical simulations. It is found that the tension–compression asymmetry of the soft Substrate not only affects the critical strain of buckling but, more importantly, may also influence the wrinkling pattern that occurs in the film–Substrate system under specified loading conditions. Due to this mechanism, the thin film subjected to equi-biaxial compression may first buckle into a hexagonal array of dimples or bulges, instead of the checkerboard pattern, and consequently evolve into labyrinths with further loading. Under non-equi-biaxial compression, the system may buckle either into a parallel bead-chain pattern or a stripe pattern, depending on the Substrate nonlinearity and the loading biaxiality. Phase diagrams are established for the wrinkling patterns in a wide range of geometric and mechanical parameters, which facilitate the design of surface patterns with desired properties and functions.
-
effect of lateral dimension on the surface wrinkling of a thin film on Compliant Substrate induced by differential growth swelling
Journal of The Mechanics and Physics of Solids, 2015Co-Authors: Yan Zhao, Yanping Cao, Xi-qiao Feng, Xue Han, Huajian GaoAbstract:Abstract Surface wrinkling in thin films on Compliant Substrates is of considerable interest for applications involving surface patterning, smart adhesion, liquid/cell shaping, particle assembly, design of flexible electronic devices, as well as mechanical characterization of thin film systems. When the in-plane size of the system is infinite, the critical wrinkling strain is known to be governed by the moduli ratio between the film and Substrate. Here we show a surprising result that the lateral dimension of the film can play a critical role in the occurrence of surface wrinkling. The basic phenomenon was established through selective UV/Ozone (UVO) exposure of a strain-free PDMS slab via composite copper grids with different meshes, followed by treatment using mixed ethanol/glycerol solvents with different volume fractions of ethanol. To understand the physics behind the experimental observations, finite element (FE) simulations were performed to establish an analytical expression for the distribution of shear tractions at the film–Substrate interface. Subsequent theoretical analysis leads to closed-form predictions for the critical growth/swelling strain for the onset of wrinkling. Our analysis reveals that the occurrence of surface wrinkling and post-wrinkling pattern evolution can be controlled by tuning the lateral size of the thin film for a given moduli ratio. These results may find broad applications in preventing surface wrinkling, creating desired surface patterns, evaluating the interfacial shear strength of a film/Substrate system and designing flexible electronic devices.
-
surface wrinkling of nanostructured thin films on a Compliant Substrate
Computational Materials Science, 2010Co-Authors: Xiupeng Zheng, Yanping Cao, Xi-qiao FengAbstract:The wrinkling of films on a soft Substrate is a critical issue of many technologically important applications and thus has attracted considerable attentions. However, the effect of the surface roughness on the buckling mode of the film remains unclear. In the present paper, the buckling of a rough film, resting on a Compliant Substrate is theoretically investigated. Dimensional analysis and large-scale finite element computations are performed to explore the wrinkling behavior of a film with periodically triangular or sinusoidal nanostructured (rough) surface patterns. The dependence relationship of the wrinkling wavelength on the geometric parameters of surface nanostructures and the elastic properties of the film and Substrate is established. Our study shows that the effects of various surface nanostructures on the film buckling can be well described by using the concept of the equivalent thickness. A relation between the equivalent thickness and the geometric parameters of the system are derived by fitting our computational results. The results reported here may be instructive for surface patterning and biomimetic design of novel materials and devices with specific surface properties. To demonstrate the potential application of the buckling method in the fabrication of hierarchical surface structures, we provide two examples inspired by the micro/nano-patterns on lotus leaves and mosquito legs.
Yanping Cao - One of the best experts on this subject based on the ideXlab platform.
-
Surface wrinkling of anisotropic films bonded on a Compliant Substrate
International Journal of Solids and Structures, 2018Co-Authors: Si-fan Yin, Yanping Cao, Xi-qiao FengAbstract:Abstract Material anisotropy regulates the instabilities of film–Substrate systems at different length scale. In this paper, we investigate the surface wrinkling and morphological evolution of an orthotropic thin film resting on a Compliant Substrate. Under different loading conditions, the system may buckle into various surface patterns, e.g., stripe, checkerboard, and herringbone, which are analyzed by using the Foppl–von Karman plate theory. The Fourier spectral method is employed to simulate the morphological evolutions of surface patterns under different loading biaxialities. We find that both loading biaxiality and material anisotropy affect the characteristics of surface wrinkling patterns and their evolutions. Stripe and checkerboard modes often emerge at the critical buckling and they tend to transform into herringbone and labyrinth patterns during postbuckling. Phase diagrams are established to reveal the dependence of surface patterns on material anisotropy, Poisson's effect, and loading biaxiality. This study may help design diverse functional surfaces and deepen our understanding of the morphogenesis of some soft biological tissues and organs.
-
non leaky modes and bandgaps of surface acoustic waves in wrinkled stiff film Compliant Substrate bilayers
Journal of The Mechanics and Physics of Solids, 2018Co-Authors: Yang Zheng, Yanping CaoAbstract:Abstract Surface acoustic wave (SAW) devices have found a wide variety of technical applications, including SAW filters, SAW resonators, microfluidic actuators, biosensors, flow measurement devices, and seismic wave shields. Stretchable/flexible electronic devices, such as sensory skins for robotics, structural health monitors, and wearable communication devices, have received considerable attention across different disciplines. Flexible SAW devices are essential building blocks for these applications, wherein piezoelectric films may need to be integrated with the Compliant Substrates. When piezoelectric films are much stiffer than soft Substrates, SAWs are usually leaky and the devices incorporating them suffer from acoustic losses. In this study, the propagation of SAWs in a wrinkled bilayer system is investigated, and our analysis shows that non-leaky modes can be achieved by engineering stress patterns through surface wrinkles in the system. Our analysis also uncovers intriguing bandgaps (BGs) related to the SAWs in a wrinkled bilayer system; these are caused by periodic deformation patterns, which indicate that diverse wrinkling patterns could be used as metasurfaces for controlling the propagation of SAWs.
-
effects of tension compression asymmetry on the surface wrinkling of film Substrate systems
Journal of The Mechanics and Physics of Solids, 2016Co-Authors: Xiao Huang, Wei Hong, Yanping Cao, Xi-qiao FengAbstract:Abstract Many soft materials and biological tissues are featured with the tension–compression asymmetry of constitutive relations. The surface wrinkling of a stiff thin film lying on a Compliant Substrate is investigated through theoretical analysis and numerical simulations. It is found that the tension–compression asymmetry of the soft Substrate not only affects the critical strain of buckling but, more importantly, may also influence the wrinkling pattern that occurs in the film–Substrate system under specified loading conditions. Due to this mechanism, the thin film subjected to equi-biaxial compression may first buckle into a hexagonal array of dimples or bulges, instead of the checkerboard pattern, and consequently evolve into labyrinths with further loading. Under non-equi-biaxial compression, the system may buckle either into a parallel bead-chain pattern or a stripe pattern, depending on the Substrate nonlinearity and the loading biaxiality. Phase diagrams are established for the wrinkling patterns in a wide range of geometric and mechanical parameters, which facilitate the design of surface patterns with desired properties and functions.
-
effect of lateral dimension on the surface wrinkling of a thin film on Compliant Substrate induced by differential growth swelling
Journal of The Mechanics and Physics of Solids, 2015Co-Authors: Yan Zhao, Yanping Cao, Xi-qiao Feng, Xue Han, Huajian GaoAbstract:Abstract Surface wrinkling in thin films on Compliant Substrates is of considerable interest for applications involving surface patterning, smart adhesion, liquid/cell shaping, particle assembly, design of flexible electronic devices, as well as mechanical characterization of thin film systems. When the in-plane size of the system is infinite, the critical wrinkling strain is known to be governed by the moduli ratio between the film and Substrate. Here we show a surprising result that the lateral dimension of the film can play a critical role in the occurrence of surface wrinkling. The basic phenomenon was established through selective UV/Ozone (UVO) exposure of a strain-free PDMS slab via composite copper grids with different meshes, followed by treatment using mixed ethanol/glycerol solvents with different volume fractions of ethanol. To understand the physics behind the experimental observations, finite element (FE) simulations were performed to establish an analytical expression for the distribution of shear tractions at the film–Substrate interface. Subsequent theoretical analysis leads to closed-form predictions for the critical growth/swelling strain for the onset of wrinkling. Our analysis reveals that the occurrence of surface wrinkling and post-wrinkling pattern evolution can be controlled by tuning the lateral size of the thin film for a given moduli ratio. These results may find broad applications in preventing surface wrinkling, creating desired surface patterns, evaluating the interfacial shear strength of a film/Substrate system and designing flexible electronic devices.
-
surface wrinkling of nanostructured thin films on a Compliant Substrate
Computational Materials Science, 2010Co-Authors: Xiupeng Zheng, Yanping Cao, Xi-qiao FengAbstract:The wrinkling of films on a soft Substrate is a critical issue of many technologically important applications and thus has attracted considerable attentions. However, the effect of the surface roughness on the buckling mode of the film remains unclear. In the present paper, the buckling of a rough film, resting on a Compliant Substrate is theoretically investigated. Dimensional analysis and large-scale finite element computations are performed to explore the wrinkling behavior of a film with periodically triangular or sinusoidal nanostructured (rough) surface patterns. The dependence relationship of the wrinkling wavelength on the geometric parameters of surface nanostructures and the elastic properties of the film and Substrate is established. Our study shows that the effects of various surface nanostructures on the film buckling can be well described by using the concept of the equivalent thickness. A relation between the equivalent thickness and the geometric parameters of the system are derived by fitting our computational results. The results reported here may be instructive for surface patterning and biomimetic design of novel materials and devices with specific surface properties. To demonstrate the potential application of the buckling method in the fabrication of hierarchical surface structures, we provide two examples inspired by the micro/nano-patterns on lotus leaves and mosquito legs.
Jizhou Song - One of the best experts on this subject based on the ideXlab platform.
-
Buckling of a stiff thin film on a bi-layer Compliant Substrate of finite thickness
International Journal of Solids and Structures, 2020Co-Authors: Chengjun Wang, Zhang Shun, Shuang Nie, Weiqiu Chen, Jizhou SongAbstract:Abstract The buckling of a stiff thin film on a Compliant Substrate has been widely studied over the past decade due to its wide applications such as stretchable electronics, micro- and nano-metrology, and surface engineering. Instead of a single-layer Compliant Substrate, a bi-layer Compliant Substrate is usually encountered in practical applications. In this paper, the buckling of a stiff thin film on a bi-layer Compliant Substrate of finite thickness is studied theoretically, numerically and experimentally. The theoretical models based on the small-deformation theory and the simple finite-deformation theory accounting for the geometry change by using the energy method are both developed and presented. The good agreement among theoretical predictions, finite element analysis and experimental measurements of the buckling behavior validates the theoretical model. The influences of finite thickness of the bi-layer Substrate and Substrate modulus ratio on the buckling wavelength and critical buckling strain are systematically investigated. The buckling configurations at various applied strains are also measured to further validate the theoretical model. These results shed light on the influence of finite Substrate thickness on buckling of the bi-layer Substrate-supported thin films and are helpful to provide design guidelines in practical applications.
-
Buckling of a stiff thin film on an elastic graded Compliant Substrate
Proceedings of The Royal Society A: Mathematical Physical and Engineering Sciences, 2017Co-Authors: Zhou Chen, Weiqiu Chen, Jizhou SongAbstract:The buckling of a stiff film on a Compliant Substrate has attracted much attention due to its wide applications such as thin-film metrology, surface patterning and stretchable electronics. An analytical model is established for the buckling of a stiff thin film on a semi-infinite elastic graded Compliant Substrate subjected to in-plane compression. The critical compressive strain and buckling wavelength for the sinusoidal mode are obtained analytically for the case with the Substrate modulus decaying exponentially. The rigorous finite element analysis (FEA) is performed to validate the analytical model and investigate the postbuckling behaviour of the system. The critical buckling strain for the period-doubling mode is obtained numerically. The influences of various material parameters on the results are investigated. These results are helpful to provide physical insights on the buckling of elastic graded Substrate-supported thin film.
-
Surface effects on the wrinkles in a stiff thin film bonded to a Compliant Substrate
Thin Solid Films, 2012Co-Authors: Yuhang Li, Jiazhong Zhang, Bo Fang, Jizhou SongAbstract:Abstract Surface effects are important to predict the mechanical behavior of nanostructures. In this paper, the wrinkling of a stiff thin film bonded to a Compliant Substrate is studied using an energy method accounting for surface elasticity and residual surface tension. The wavelength, critical buckling strain and amplitude are obtained analytically. These results provide valuable guide to the precise design and control of the wrinkling profile in many applications ranging from stretchable electronics to micro/nano scale surface patterning and precision metrology.
-
Buckling of a stiff thin film on a Compliant Substrate in large deformation
International Journal of Solids and Structures, 2008Co-Authors: Jizhou Song, John A. Rogers, Yonggang Huang, Hanqing Jiang, Zhuangjian Liu, Dahl-young Khang, Chan Ghee KohAbstract:A finite-deformation theory is developed to study the mechanics of thin buckled films on Compliant Substrates. Perturbation analysis is performed for this highly nonlinear system to obtain the analytical solution. The results agree well with experiments and finite element analysis in wavelength and amplitude. In particular, it is found that the wavelength depends on the strain. Based on the accurate wavelength and amplitude, the membrane and peak strains in thin films, and stretchability and compressibility of the system are also obtained analytically. 2008 Elsevier Ltd. All rights reserved.
Zijing Ding - One of the best experts on this subject based on the ideXlab platform.
-
Thermocapillary thin-film flows on a Compliant Substrate.
Physical Review E, 2019Co-Authors: Youchuang Chao, Zijing DingAbstract:We study the dynamics of a thin liquid film on a Compliant Substrate in the presence of thermocapillary effect. A set of long-wave equations are derived to investigate the effects of fluid gravity (G), fluid inertia (Re), and Marangoni stresses (Ma) on the dynamics of the liquid film and the Compliant Substrate. By performing linear stability analysis and time-dependent computations of the long-wave equations, we examine two different cases: thin-film flows on a horizontally Compliant Substrate (β=0, where β is the inclined angle) and down a vertically Compliant Substrate (β=π/2), respectively. For β=0, we neglect fluid inertia and identify two different modes: (1) sinuous mode, where the deformations of liquid-air and liquid-Substrate interfaces are in phase, which is induced by the fluid gravity, and (2) varicose mode, where the deformations of two interfaces are in phase opposition, which is induced by the Marangoni stresses. For β=π/2, we consider a weak fluid inertia and only observe the varicose mode driven by fluid inertia and Marangoni stresses. However, because the gravity direction is parallel to the Substrate, the fluid gravity modifies the varicose mode, making the deformations of two interfaces out of phase. In particular, we also seek the nonlinear traveling-wave solutions in the case of β=π/2, revealing that fluid inertia and/or heating effect enhance the height and speed of the traveling waves. In both cases, the introduction of a strong wall heating gives rise to large deformations of both the thin liquid film and the Compliant Substrate.
-
thermocapillary thin film flows on a Compliant Substrate
Physical Review E, 2019Co-Authors: Youchuang Chao, Zijing DingAbstract:We study the dynamics of a thin liquid film on a Compliant Substrate in the presence of thermocapillary effect. A set of long-wave equations are derived to investigate the effects of fluid gravity $(G)$, fluid inertia (Re), and Marangoni stresses (Ma) on the dynamics of the liquid film and the Compliant Substrate. By performing linear stability analysis and time-dependent computations of the long-wave equations, we examine two different cases: thin-film flows on a horizontally Compliant Substrate $(\ensuremath{\beta}=0$, where $\ensuremath{\beta}$ is the inclined angle) and down a vertically Compliant Substrate $(\ensuremath{\beta}=\ensuremath{\pi}/2)$, respectively. For $\ensuremath{\beta}=0$, we neglect fluid inertia and identify two different modes: (1) sinuous mode, where the deformations of liquid-air and liquid-Substrate interfaces are in phase, which is induced by the fluid gravity, and (2) varicose mode, where the deformations of two interfaces are in phase opposition, which is induced by the Marangoni stresses. For $\ensuremath{\beta}=\ensuremath{\pi}/2$, we consider a weak fluid inertia and only observe the varicose mode driven by fluid inertia and Marangoni stresses. However, because the gravity direction is parallel to the Substrate, the fluid gravity modifies the varicose mode, making the deformations of two interfaces out of phase. In particular, we also seek the nonlinear traveling-wave solutions in the case of $\ensuremath{\beta}=\ensuremath{\pi}/2$, revealing that fluid inertia and/or heating effect enhance the height and speed of the traveling waves. In both cases, the introduction of a strong wall heating gives rise to large deformations of both the thin liquid film and the Compliant Substrate.
Arezki Boudaoud - One of the best experts on this subject based on the ideXlab platform.
-
The Buckling of a Swollen Thin Gel Layer Bound to a Compliant Substrate
Journal of Applied Mechanics, 2008Co-Authors: Eric Sultan, Arezki BoudaoudAbstract:Gels are used to design bilayered structures with high residual stresses. The swelling of a thin layer on a Compliant Substrate leads to compressive stresses. The postbuckling of this layer is investigated experimentally; the wavelengths and amplitudes of the resulting modes are measured. A simplified model with a self-avoiding rod on a Winkler foundation is in semiquantitative agreement with experiments and reproduces the observed cusplike folds.
-
buckling of a stiff film bound to a Compliant Substrate part iii herringbone solutions at large buckling parameter
Journal of The Mechanics and Physics of Solids, 2008Co-Authors: Basile Audoly, Arezki BoudaoudAbstract:We study the buckling of a compressed thin elastic film bonded to a Compliant Substrate. An asymptotic solution of the equations for a plate on an elastic foundation is obtained in the limit of large residual stress in the film. In this limit, the film's shape is given by a popular origami folding, the Miura-ori, and is composed of parallelograms connected by dihedral folds. This asymptotic solution corresponds to the herringbone patterns reported previously in experiments: the crests and valleys of the pattern define a set of parallel, sawtooth-like curves. The kink angle obtained when observing these crests and valleys from above are shown to be right angles under equi-biaxial loading, in agreement with the experiments. The absolute minimum of energy corresponds to a pattern with very slender parallelograms; in the experiments, the wavelength is instead selected by the history of applied load.
-
buckling of a stiff film bound to a Compliant Substrate part i formulation linear stability of cylindrical patterns secondary bifurcations
Journal of The Mechanics and Physics of Solids, 2008Co-Authors: Basile Audoly, Arezki BoudaoudAbstract:The buckling of a thin elastic film bound to a Compliant Substrate is studied: we analyze the different patterns that arise as a function of the biaxial residual compressive stress in the film. We first clarify the boundary conditions to be used at the interface between film and Substrate. We carry out the linear stability analysis of the classical pattern made of straight stripes, and point out secondary instabilities leading to the formation of undulating stripes, varicose, checkerboard or hexagonal patterns. Straight stripes are found to be stable in a narrow window of load parameters only. We present a weakly nonlinear post-buckling analysis of these patterns: for equi-biaxial residual compression, straight wrinkles are never stable and square checkerboard patterns are found to be optimal just above threshold; for anisotropic residual compression, straight wrinkles are present above a primary threshold and soon become unstable with respect to undulating stripes. These results account for many of the previously published experimental or numerical results on this geometry.
-
buckling of a stiff film bound to a Compliant Substrate part ii a global scenario for the formation of herringbone pattern
Journal of The Mechanics and Physics of Solids, 2008Co-Authors: Basile Audoly, Arezki BoudaoudAbstract:We study the buckling of a thin compressed elastic film bonded to a Compliant Substrate. We focus on a family of buckling patterns, such that the film profile is generated by two functions of a single variable. This family includes the unbuckled configuration, the classical primary mode made of straight stripes, as well the pattern with undulating stripes obtained by a secondary instability investigated in the first companion paper, and the herringbone pattern studied in last companion paper. A simplified buckling model relevant for the analysis of these patterns is introduced. It is solved analytically for moderate or for large residual compressive stress in the film. Numerical simulations are presented, based on an efficient implementation. Overall, the analysis provides a global picture for the formation of herringbone patterns under increasing residual stress. The film shape is shown to converge at large load to a developable shape with ridges. The wavelength of the pattern, selected in a first place by the primary buckling bifurcation, is frozen during the subsequent increase of loading.