Attachment of zebra and quagga mussel adhesive plaques to diverse substrates

Like marine mussels, freshwater zebra and quagga mussels adhere via the byssus, a proteinaceous attachment apparatus. Attachment to various surfaces allows these invasive mussels to rapidly spread, however the adhesion mechanism is not fully understood. While marine mussel adhesion mechanics has been studied at the individual byssal-strand level, freshwater mussel adhesion has only been characterized through whole-mussel detachment, without direct interspecies comparisons on different substrates. Here, adhesive strength of individual quagga and zebra mussel byssal plaques were measured on smooth substrates with varying hydrophobicity—glass, PVC, and PDMS. With increased hydrophobicity of substrates, adhesive failures occurred more frequently, and mussel adhesion strength decreased. A new failure mode termed 'footprint failure' was identified, where failure appeared to be adhesive macroscopically, but a microscopic residue remained on the surface. Zebra mussels adhered stronger and more frequently on PDMS than quagga mussels. While their adhesion strengths were similar on PVC, there were differences in the failure mode and the plaque-substrate interface ultrastructure. Comparisons with previous marine mussel studies demonstrated that freshwater mussels adhere with comparable strength despite known differences in protein composition. An improved understanding of freshwater mussel adhesion mechanics may help explain spreading dynamics and will be important in developing effective antifouling surfaces.

Myofibroblast differentiation is governed by adhesion mechanics, and inhibition of the stress sensor Talin2 reverses lung fibrosis

Fibrosis is involved in 45% of deaths in the United States, and no treatment exists to reverse progression of the disease. In order to find novel targets for fibrosis therapeutics, we developed a model for the differentiation of monocytes to myofibroblasts that allowed us to screen for proteins involved in myofibroblast differentiation. We assessed these screening results for proteins to target for novel fibrosis therapeutics. Here we test whether inhibition of a novel protein target generated by our model, talin2, can prevent and even reverse myofibroblast differentiation. We find that knockdown of talin2 de-differentiates myofibroblasts, altering myofibroblast morphology, α-smooth muscle actin and collagen content, and the secretome. Talin2 inhibition reverses bleomycin-induced lung fibrosis in mice. Talin2 inhibition could be a novel treatment for reversing lung fibrosis.

Adhesion of an elastic sphere on a tensioned membrane

Inspirited by the fact that classical models of adhesion contact (such as the Johnson–Kendall–Roberts model, Young’s equation or the Neumann equation) cannot be directly applied to adhesion of an elastic sphere on a membrane, the present work aims to develop an explicit general model for axisymmetric adhesion mechanics of an elastic sphere on a tensioned circular membrane. An explicit expression for the potential energy of the sphere–membrane system is derived, and explicit equations are given to determine the adhesion equilibrium state. The validity and accuracy of the proposed model are verified by good agreement between the predicted results and known results on both adhesion of a rigid sphere on a membrane and the critical condition for full wrapping of a rigid sphere by a membrane of non-zero bending rigidity.

Adhesion and Adhesion Mechanics. Features of the Theory and its Possibilities

The article is intended to convince the reader of the need to characterise the contact of the adhesive with the substrate. The concept of contact layer and intensity of adhesive interaction is introduced. The specific examples demonstrate the effectiveness of the proposed approach for solving boundary problems with stress concentration The Cauchy problem in this case is strictly solved.

Graphene Adhesion Mechanics on Iron Substrates: Insight from Molecular Dynamic Simulations

The adhesion feature of graphene on metal substrates is important in graphene synthesis, transfer and applications, as well as for graphene-reinforced metal matrix composites. We investigate the adhesion energy of graphene nanosheets (GNs) on iron substrate using molecular dynamic (MD) simulations. Two Fe–C potentials are examined as Lennard–Jones (LJ) pair potential and embedded-atom method (EAM) potential. For LJ potential, the adhesion energies of monolayer GN are 0.47, 0.62, 0.70 and 0.74 J/m2 on the iron {110}, {111}, {112} and {100} surfaces, respectively, compared to the values of 26.83, 24.87, 25.13 and 25.01 J/m2 from EAM potential. When the number of GN layers increases from one to three, the adhesion energy from EAM potential increases. Such a trend is not captured by LJ potential. The iron {110} surface is the most adhesive surface for monolayer, bilayer and trilayer GNs from EAM potential. The results suggest that the LJ potential describes a weak bond of Fe–C, opposed to a hybrid chemical and strong bond from EAM potential. The average vertical distances between monolayer GN and four iron surfaces are 2.0–2.2 Å from LJ potential and 1.3–1.4 Å from EAM potential. These separations are nearly unchanged with an increasing number of layers. The ABA-stacked GN is likely to form on lower-index {110} and {100} surfaces, while the ABC-stacked GN is preferred on higher-index {111} surface. Our insights of the graphene adhesion mechanics might be beneficial in graphene growing, surface engineering and enhancement of iron using graphene sheets.

A Refined JKR Model for Adhesion of a Rigid Sphere on a Soft Elastic Substrate

Surface energy outside the contact zone, which is ignored in the classical Johnson–Kendall–Roberts (JKR) model, can play an essential role in adhesion mechanics of soft bodies. In this work, based on a simple elastic foundation model for a soft elastic half space with constant surface tension, an explicit expression for the change of surface energy outside the contact zone is proposed for a soft elastic substrate indented by a rigid sphere in terms of two JKR-type variables (δ, a), where a is the radius of the contact zone and δ is the indentation depth of the rigid sphere. The derived expression is added to the classical JKR model to achieve two explicit equations for the determination of the two JKR variables (δ, a). The results given by the present model are demonstrated with detailed comparison with known results reported in recent literature, which verified the validity and robust accuracy of the present method. In particular, the present model confirms that the change of surface energy of the substrate can play an essential role in micro/nanoscale contact of soft materials (defined by W/(E*R)≥0.1, where W is the adhesive energy, E* is the substrate elasticity, and R is the rigid sphere radius). The present model offers a simpler analytical method for adhesion mechanics of a rigid sphere on a soft elastic substrate when compared with several existing methods proposed in recent literature that request more substantial numerical calculations.