The role of nonlinear substrate elasticity in the wrinkling of thin films

The role of substrate nonlinearity in the stability of wrinkling of thin films bonded to compliant substrates is investigated within the initial post-bifurcation range when wrinkling first emerges. A fully nonlinear neo-Hookean bilayer composed of a thin film on a deep substrate is analysed for a wide range of the film–substrate stiffness ratio, from films that are very stiff compared with the substrate to those only slightly stiffer. Substrate pre-stretch prior to film attachment is shown to have a significant effect on the nonlinearity relevant to wrinkling. Two dimensionless parameters are identified that control the stability and mode shape evolution of the bilayer: one specifying arbitrary uniform substrate pre-stretch and the other a stretch-modified modulus ratio. For systems with film stiffness greater than about five times that of the substrate the wrinkling bifurcation is stable, whereas for systems with smaller relative film stiffness bifurcation can be unstable, especially if substrate pre-stretch is not tensile.

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Wrinkling Phenomena in Neo-Hookean Film/Substrate Bilayers

Journal of Applied Mechanics ◽

10.1115/1.4005960 ◽

2012 ◽

Vol 79 (3) ◽

Cited By ~ 162

Author(s):

Yanping Cao ◽

John W. Hutchinson

Keyword(s):

Finite Element ◽

Critical Strain ◽

Full Range ◽

Period Doubling ◽

Modulus Ratio ◽

Layer System ◽

Mountain Ridge ◽

Compliant Substrates ◽

Film Substrate

Wrinkling modes are determined for a two-layer system comprised of a neo-Hookean film bonded to an infinitely deep neo-Hookean substrate with the entire bilayer undergoing compression. The full range of the film/substrate modulus ratio is considered from the limit of a traction-free homogeneous substrate to very stiff films on compliant substrates. The role of substrate prestretch is considered wherein an unstretched film is bonded to a prestretched substrate with wrinkling arising as the stretch in the substrate is relaxed. An exact bifurcation analysis reveals the critical strain in the film at the onset of wrinkling. Numerical simulations carried out within a finite element framework uncover advanced post-bifurcation modes including period-doubling, folding and a newly identified mountain ridge mode.

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Multimodal Surface Instabilities in Curved Film–Substrate Structures

Journal of Applied Mechanics ◽

10.1115/1.4036940 ◽

2017 ◽

Vol 84 (8) ◽

Cited By ~ 22

Author(s):

Ruike Zhao ◽

Xuanhe Zhao

Keyword(s):

Thin Films ◽

Mechanical Properties ◽

Numerical Simulation ◽

Period Doubling ◽

Tubular Structures ◽

Modulus Ratio ◽

Future Design ◽

Mismatch Strain ◽

Curved Structures ◽

Film Substrate

Structures of thin films bonded on thick substrates are abundant in biological systems and engineering applications. Mismatch strains due to expansion of the films or shrinkage of the substrates can induce various modes of surface instabilities such as wrinkling, creasing, period doubling, folding, ridging, and delamination. In many cases, the film–substrate structures are not flat but curved. While it is known that the surface instabilities can be controlled by film–substrate mechanical properties, adhesion and mismatch strain, effects of the structures’ curvature on multiple modes of instabilities have not been well understood. In this paper, we provide a systematic study on the formation of multimodal surface instabilities on film–substrate tubular structures with different curvatures through combined theoretical analysis and numerical simulation. We first introduce a method to quantitatively categorize various instability patterns by analyzing their wave frequencies using fast Fourier transform (FFT). We show that the curved film–substrate structures delay the critical mismatch strain for wrinkling when the system modulus ratio between the film and substrate is relatively large, compared with flat ones with otherwise the same properties. In addition, concave structures promote creasing and folding, and suppress ridging. On the contrary, convex structures promote ridging and suppress creasing and folding. A set of phase diagrams are calculated to guide future design and analysis of multimodal surface instabilities in curved structures.

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Stabilizing electrodeposition in elastic solid electrolytes containing immobilized anions

Science Advances ◽

10.1126/sciadv.1600320 ◽

2016 ◽

Vol 2 (7) ◽

pp. e1600320 ◽

Cited By ~ 128

Author(s):

Mukul D. Tikekar ◽

Lynden A. Archer ◽

Donald L. Koch

Keyword(s):

Elastic Solid ◽

Present Theory ◽

Metal Electrode ◽

Mitigation Strategies ◽

Factors Affecting ◽

Wide Range ◽

Current Densities ◽

Morphological Instabilities ◽

The Stability

Ion transport–driven instabilities in electrodeposition of metals that lead to morphological instabilities and dendrites are receiving renewed attention because mitigation strategies are needed for improving rechargeability and safety of lithium batteries. The growth rate of these morphological instabilities can be slowed by immobilizing a fraction of anions within the electrolyte to reduce the electric field at the metal electrode. We analyze the role of elastic deformation of the solid electrolyte with immobilized anions and present theory combining the roles of separator elasticity and modified transport to evaluate the factors affecting the stability of planar deposition over a wide range of current densities. We find that stable electrodeposition can be easily achieved even at relatively high current densities in electrolytes/separators with moderate polymer-like mechanical moduli, provided a small fraction of anions are immobilized in the separator.

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Salesperson Solution Involvement and Sales Performance: The Contingent Role of Supplier Firm and Customer–Supplier Relationship Characteristics

Journal of Marketing ◽

10.1509/jm.15.0342 ◽

2017 ◽

Vol 81 (4) ◽

pp. 144-164 ◽

Cited By ~ 31

Author(s):

Nikolaos G. Panagopoulos ◽

Adam A. Rapp ◽

Jessica L. Ogilvie

Keyword(s):

Sales Performance ◽

Product Portfolio ◽

Data Set ◽

Relational Processes ◽

Wide Range ◽

Performance Effects ◽

Time Lagged ◽

The Stability ◽

Supplier Relationship

Salespeople play a crucial role in their firms’ efforts to provide customer solutions. However, little research has examined how salesperson involvement in customer solutions can be conceptualized, whether it pays off, and what boundary conditions might heighten its performance effects. This study addresses these gaps and offers a conceptualization of salesperson solution involvement by focusing on the set of salesperson-related activities that enact the four relational processes inherent in customer solutions. The authors collect a unique data set that includes a wide range of firms, industries, and countries, as well as the perspectives of both salespeople and customers, across five studies. Results validate the stability of the conceptualization across contexts. They also reveal that salesperson solution involvement is systematically related to increases in both subjective and objective, time-lagged measures of sales performance. Finally, results show that the performance effects of salesperson solution involvement are amplified under higher levels of firm's product portfolio scope, sales unit cross-functional cooperation, and customer–supplier relationship tie strength. Surprisingly, customer adaptiveness is not found to moderate the performance effects of salesperson solution involvement.

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The Contribution of NMR Spectroscopy in Understanding Perovskite Stabilization Phenomena

Nanomaterials ◽

10.3390/nano11082024 ◽

2021 ◽

Vol 11 (8) ◽

pp. 2024

Author(s):

Federica Aiello ◽

Sofia Masi

Keyword(s):

Thin Films ◽

Solid State ◽

Nmr Spectroscopy ◽

Research Attention ◽

Perovskite Materials ◽

Hybrid Perovskite ◽

Physico Chemical ◽

Tool Set ◽

The Stability

Although it has been exploited since the late 1900s to study hybrid perovskite materials, nuclear magnetic resonance (NMR) spectroscopy has only recently received extraordinary research attention in this field. This very powerful technique allows the study of the physico-chemical and structural properties of molecules by observing the quantum mechanical magnetic properties of an atomic nucleus, in solution as well as in solid state. Its versatility makes it a promising technique either for the atomic and molecular characterization of perovskite precursors in colloidal solution or for the study of the geometry and phase transitions of the obtained perovskite crystals, commonly used as a reference material compared with thin films prepared for applications in optoelectronic devices. This review will explore beyond the current focus on the stability of perovskites (3D in bulk and nanocrystals) investigated via NMR spectroscopy, in order to highlight the chemical flexibility of perovskites and the role of interactions for thermodynamic and moisture stabilization. The exceptional potential of the vast NMR tool set in perovskite structural characterization will be discussed, aimed at choosing the most stable material for optoelectronic applications. The concept of a double-sided characterization in solution and in solid state, in which the organic and inorganic structural components provide unique interactions with each other and with the external components (solvents, additives, etc.), for material solutions processed in thin films, denotes a significant contemporary target.

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Kinetics of Membrane Spreading on Compliant Bio-Adhesive Substrates

ASME 2010 First Global Congress on NanoEngineering for Medicine and Biology ◽

10.1115/nemb2010-13321 ◽

2010 ◽

Author(s):

Alireza Sarvestani

Keyword(s):

Focal Adhesion ◽

Early Stage ◽

Thermodynamic Force ◽

Mechanical Stiffness ◽

Compliant Substrates ◽

Wide Range ◽

Adhesion Zone ◽

Spread Area ◽

Substrate Elasticity ◽

Kinetics Of

The contact formation between cell membrane and a bio-adhesive substrate is driven by binding between transmembrane mobile receptors (e.g., integrin) and complementary ligand molecules on the substrate (fibronectin, collagen, etc.) This short range specific adhesion is alleviated by a phalanx of interfacial non-specific forces. In addition to cell-substrate interfacial interactions, cell adhesion can be mediated by a wide range of substrate physiochemical properties. In particular, mechanical stiffness of the substrate has been recognized as one of the major regulators for bio-adhesion. Cells in general, exhibit an apparent adhesion preference for stiffer substrates and switch from a round to spread morphology as the substrate stiffness increases. Understanding the mechano-chemical pathways mediating the interplay between the substrate properties and cell behavior could be critical for effective performance of synthetic biomaterials in tissue engineering applications. In this study, we consider the effect of substrate elasticity on the dynamics of membrane spreading and growth of focal adhesion zone. The formation and growth of the focal adhesion points during the early stage of adhesion process is a result of spontaneous spreading of membrane on the substrate. This can be considered as a non-equilibrium kinetic process which is controlled by the diffusibility of receptor molecules. In order to study the effect of substrate elasticity on the kinetics of membrane-substrate association, receptors are assumed as ideal solute particles laterally diffusing within the plane of the membrane until they are stabilized through association with their complementary ligands which are immobilized on the surface of a compliant substrate. Considering different mechanical stiffness for the substrates, the displacement and speed of spreading at the edge of adhesion zone are predicted as a function of time. Results show that decreasing the stiffness of bio-adhesive substrates reduces the rate of membrane spreading, due to a weaker thermodynamic force which drives the membrane-substrate association. This mechanism restrains the growth of focal adhesion zones on compliant substrates and can be considered as a reason for smaller spread area of the cells after stabilization of adhesion.

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A new paradigm in thin film indentation

Journal of Materials Research ◽

10.1557/jmr.2010.0228 ◽

2010 ◽

Vol 25 (9) ◽

pp. 1671-1678 ◽

Cited By ~ 29

Author(s):

Bo Zhou ◽

Barton C. Prorok

Keyword(s):

Thin Film ◽

Transfer Model ◽

New Paradigm ◽

Compliant Substrates ◽

Wide Range ◽

Stiffness Method ◽

Elastic Interface ◽

Film Substrate ◽

Influence Behavior ◽

Membrane Deflection

A new method to accurately and reliably extract the actual Young's modulus of a thin film on a substrate by indentation was developed. The method involved modifying the discontinuous elastic interface transfer model to account for substrate effects that were found to influence behavior a few nanometers into a film several hundred nanometers thick. The method was shown to work exceptionally well for all 25 different combinations of five films on five substrates that encompassed a wide range of compliant films on stiff substrates to stiff films on compliant substrates. A predictive formula was determined that enables the film modulus to be calculated as long as one knows the film thickness, substrate modulus, and bulk Poisson's ratio of the film and the substrate. The calculated values of the film modulus were verified with prior results that used the membrane deflection experiment and resonance-based methods. The greatest advantages of the method are that the standard Oliver and Pharr analysis can be used, and that it does not require the continuous stiffness method, enabling any indenter to be used. The film modulus then can be accurately determined by simply averaging a handful of indents on a film/substrate composite.

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Mobile-surface bubbles and droplets coalesce faster but bounce stronger

Science Advances ◽

10.1126/sciadv.aaw4292 ◽

2019 ◽

Vol 5 (10) ◽

pp. eaaw4292 ◽

Cited By ~ 6

Author(s):

Ivan U. Vakarelski ◽

Fan Yang ◽

Yuan Si Tian ◽

Er Qiang Li ◽

Derek Y. C. Chan ◽

...

Keyword(s):

Liquid Interfaces ◽

Oil Processing ◽

Surface Mobility ◽

Wide Range ◽

Multiphase Systems ◽

Liquid Emulsion ◽

Emulsion Systems ◽

The Stability ◽

Interfacial Mobility

Enhancing the hydrodynamic interfacial mobility of bubbles and droplets in multiphase systems is expected to reduce the characteristic coalescence times and thereby affect the stability of gas or liquid emulsions that are of wide industrial and biological importance. However, by comparing the controlled collision of bubbles or water droplets with mobile or immobile liquid interfaces, in a pure fluorocarbon liquid, we demonstrate that collisions involving mobile surfaces result in a significantly stronger series of rebounds before the rapid coalescence event. The stronger rebound is explained by the lower viscous dissipation during collisions involving mobile surfaces. We present direct numerical simulations to confirm that the observed rebound is enhanced with increased surface mobility. These observations require a reassessment of the role of surface mobility for controlling the dynamic stability of gas or liquid emulsion systems relevant to a wide range of processes, from microfluidics and pharmaceuticals to food and crude oil processing.

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Role of Film-Substrate Interaction in Determining the Morphology of Thin Films

MRS Proceedings ◽

10.1557/proc-103-13 ◽

1987 ◽

Vol 103 ◽

Cited By ~ 4

Author(s):

Marcia H. Grabow ◽

George H. Gilmer

Keyword(s):

Thin Films ◽

Molecular Dynamics ◽

Computer Simulations ◽

Substrate Binding ◽

Equilibrium Structure ◽

Metastable States ◽

Growth Mode ◽

Substrate Interaction ◽

Film Substrate

ABSTRACTThe equilibrium structure and metastable states of thin films have been investigated using molecular dynamics computer simulations. The energy as a function of coverage for a variety of film/substrate systems has been determined, and this information has been used to determine the growth mode and the conditions under which the film is dislocation free. In particular, the influence of the strength of the film-substrate binding will be discussed.

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