Contact Instability of a Soft Elastic Film Bonded to a Patterned Substrate

Sarkar, Jayati; Annepu, Hemalatha; Sharma, Ashutosh

doi:10.1080/00218464.2011.557332

Cited by 18 publications

(21 citation statements)

References 39 publications

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“…Elastic contact lithography (ECL) is an approach that aims to align the random instability patterns by imposing lateral confinement. [331][332][333][342][343][344][345] Strategies adopted in this regard include: (1) the use of a topographically patterned stamp; [331][332][333]342,345 (2) using a topographically patterned substrate; 343,344 and (3) shearing of a flat stamp while it is in contact with the film. 331,332 ECL has been implemented in an elastic bilayer to derive the advantages of feature dimension miniaturization as well.…”

Section: Elastic Contact Lithographymentioning

confidence: 99%

Instability, self-organization and pattern formation in thin soft films

2015

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The free surface of a thin soft polymer film is often found to become unstable and self-organizes into various meso-scale structures. In this article we classify the instability of a thin polymer film into three broad categories, which are: category 1: instability of an ultra-thin (<100 nm) viscous film engendered by amplification of thermally excited surface capillary waves due to interfacial dispersive van der Waals forces; category 2: instability arising from the attractive inter-surface interactions between the free surface of a soft film exhibiting room temperature elasticity and another rigid surface in its contact proximity; and category 3: instability caused by an externally applied field such as an electric field or a thermal gradient, observed in both viscous and elastic films. We review the salient features of each instability class and highlight how characteristic length scales, feature morphologies, evolution pathways, etc. depend on initial properties such as film thickness, visco-elasticity (rheology), residual stress, and film preparation conditions. We emphasize various possible strategies for aligning and ordering of the otherwise isotropic structures by combining the essential concepts of bottom-up and top-down approaches. A perspective, including a possible future direction of research, novelty and limitations of the methods, particularly in comparison to the existing patterning techniques, is also presented for each setting.

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Section: Elastic Contact Lithographymentioning

confidence: 99%

Instability, self-organization and pattern formation in thin soft films

2015

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“…By simplifying the detailed molecular structures of the lipids and polymers, our coarse-grained simulations can explore the system on time and length scales relevant to the interactions between multiple polymers and the mixed lipid membrane. This allows us to extensively explore the effects of the cooperation between the cationic segments of each polymer with different ionization degrees and the effects of the competitions between the anchoring polymers on the lateral sequestering and corresponding mobility of the charged lipids, thereby providing a better understanding of the biophysical mechanism and offering insight into the innovation of novel biotechnologies for signaling-lipid modulation. ,− In Section , we briefly depict our MC model and the detailed parameters in the simulation. In Section , we analyze the effects of the concentration and ionization degree of the anchoring cationic polymers on the sequestering of different anionic lipids.…”

Section: Introductionmentioning

confidence: 99%

Effects of Concentration and Ionization Degree of Anchoring Cationic Polymers on the Lateral Heterogeneity of Anionic Lipid Monolayers

Duan

Zhang

et al. 2017

J. Phys. Chem. B

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We employed coarse-grained Monte Carlo simulations to investigate a system composed of cationic polymers and a phosphatidyl-choline membrane monolayer, doped with univalent anionic phosphatidylserine (PS) and tetravalent anionic phosphatidylinositol 4,5-bisphosphate (PIP) lipid molecules. For this system, we consider the conditions under which multiple cationic polymers can anchor onto the monolayer and explore how the concentration and ionization degree of the polymers affect the lateral rearrangement and fluidity of the negatively charged lipids. Our work shows that the anchoring cationic polymers predominantly bind the tetravalent anionic PIP lipids and drag the PIP clusters to migrate on the monolayer. The polymer/PIP binding is found to be drastically enhanced by increasing the polymer ionization fraction, which causes the PIP lipids to form into larger clusters and reduces the mobility of the polymer/PIP complexes. As expected, stronger competition effects between anchoring polymers occur at higher polymer concentrations, for which each anchoring polymer partially dissociates from the monolayer and hence sequesters a smaller PIP cluster. The desorbed segments of the anchored polymers exhibit a faster mobility on the membrane, whereas the PIP clusters are closely restrained by the limited adhering cationic segments of anchoring polymers. We further demonstrate that the PIP molecules display a hierarchical mobility in the PIP clusters, which is regulated by the synergistic effect between the cationic segments of the polymers. The PS lipids sequester in the vicinity of the polymer/PIP complexes if the tetravalent PIP lipids cannot sufficiently neutralize the cationic polymers. Finally, we illustrate that the increase in the ionic concentration of the solution weakens the lateral clustering and the mobility heterogeneity of the charged lipids. Our work thus provides a better understanding of the fundamental biophysical mechanism of the concentration gradients and the hierarchical mobility of the anionic lipids in the membrane caused by the cationic polymer anchoring on length and time scales that are generally inaccessible by atomistic models. It also offers insight into the development and design of novel biological applications on the basis of the modulation of signaling lipids.

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“…The complex coacervates of charged macromolecules and liposomes have been extensively studied via a variety of experimental techniques [ 1 , 4 , 6 , 7 , 8 , 9 , 10 ], such as X-ray scattering, transmission electron microscopy, fluorescence resonance energy transfer measurements, etc. These studies have demonstrated that the anchored charged macromolecules can adjust the fraction of free anionic lipids and cause the mobility heterogeneity of the membrane through the electrostatic sequestration of the anionic lipids, thereby offering useful information for the development of biological and medical applications [ 11 , 12 , 13 , 14 , 15 , 16 ]. However, it remains a significant challenge to investigate the macromolecule/membrane complexes at a molecular scale via experimental approaches, due to the hydrolysis and fast turnover of the anionic lipids in vivo [ 1 ].…”

Section: Introductionmentioning

confidence: 99%

Spatial Rearrangement and Mobility Heterogeneity of an Anionic Lipid Monolayer Induced by the Anchoring of Cationic Semiflexible Polymer Chains

Duan

Zhang

et al. 2016

Polymers

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Abstract:We use Monte Carlo simulations to investigate the interactions between cationic semiflexible polymer chains and a model fluid lipid monolayer composed of charge-neutral phosphatidyl-choline (PC), tetravalent anionic phosphatidylinositol 4,5-bisphosphate (PIP 2 ), and univalent anionic phosphatidylserine (PS) lipids. In particular, we explore how chain rigidity and polymer concentration influence the spatial rearrangement and mobility heterogeneity of the monolayer under the conditions where the cationic polymers anchor on the monolayer. We find that the anchored cationic polymers only sequester the tetravalent PIP 2 lipids at low polymer concentrations, where the interaction strength between the polymers and the monolayer exhibits a non-monotonic dependence on the degree of chain rigidity. Specifically, maximal anchoring occurs at low polymer concentrations, when the polymer chains have an intermediate degree of rigidity, for which the PIP 2 clustering becomes most enhanced and the mobility of the polymer/PIP 2 complexes becomes most reduced. On the other hand, at sufficiently high polymer concentrations, the anchoring strength decreases monotonically as the chains stiffen-a result that arises from the pronounced competitions among polymer chains. In this case, the flexible polymers can confine all PIP 2 lipids and further sequester the univalent PS lipids, whereas the stiffer polymers tend to partially dissociate from the monolayer and only sequester smaller PIP 2 clusters with greater mobilities. We further illustrate that the mobility gradient of the single PIP 2 lipids in the sequestered clusters is sensitively modulated by the cooperative effects between anchored segments of the polymers with different rigidities. Our work thus demonstrates that the rigidity and concentration of anchored polymers are both important parameters for tuning the regulation of anionic lipids.

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Contact Instability of a Soft Elastic Film Bonded to a Patterned Substrate

Cited by 18 publications

References 39 publications

Instability, self-organization and pattern formation in thin soft films

Instability, self-organization and pattern formation in thin soft films

Effects of Concentration and Ionization Degree of Anchoring Cationic Polymers on the Lateral Heterogeneity of Anionic Lipid Monolayers

Spatial Rearrangement and Mobility Heterogeneity of an Anionic Lipid Monolayer Induced by the Anchoring of Cationic Semiflexible Polymer Chains

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