adhesion

Hello:  I would be interested in any comment about this preprint on fibrillar viscoelastic adhesion, originally devised by Schargott Popov and Gorb, where we use for the first time not only the Schapery model for nucleation of cracks, but also the Shrimali and Lopez Pamies, which leads to quite stronger enhancement of adhesion (the limit is the square of the Schapery one), and pull-off with no real prior propagation phase.  Propagation with Schapery nucleation criterion is found to be qualitatively similar to the Schapery and Persson-Brener propagation theories, except that the reference ve

In unidirectional sliding of rubber contacts on smooth hard surface it has been found that contact shrinks largely in longitudinal directions, and generally much less in the transverse direction, and two explanations have been suggested to explain this: one is the effect of mixed mode fracture mechanics in the presence of adhesion (with mode II reducing adhesion and mode III less clear), and another uniquely based on finite strain effects even for a simple material model as neo-Hookean hyperelastic material.

Considerable research has been conducted on shape of pillar ends for optimal adhesion. In experiments with elastomers it has been found that mushrooms-ended ones are superior to flat-ended ones, but early experiments have suggested an extremely strong scaling in strength with pillar radius (del Campo et al Langmuir;23 :10235-43, 2007). We discuss various theories and experimental results on scaling of strength, and in particular we elaborate recent experiments on single pillars with mushroom ends finding that the scaling on strength is much less surprising.

dear Friends

We are hiring 2 post-docs soon in Italy at the Department of Mechanics DMMM of the Politecnico di BARI.  The subject is here described.

The Gordon Research Conference on the Science of Adhesion is this summer (23-28 July 2023).  The meeting will be held on the campus of Mount Holyoke College in western Massachusetts and will have more than 20 invited talks from world leaders in the fields of adhesion, soft matter, and materials. This is a great meeting for students and early career researchers to get connected to the community. Poster presentations are strongly encouraged from all participants, and poster abstracts can still be submitted.

Dear friends, I want to share our recent work on the shape characteristics of 2D crystal blisters. Micro- and nano-sized blisters can form spontaneously when two-dimensional (2D) crystals are transferred onto substrates because liquid molecules that are initially adsorbed on 2D material and substrate surfaces can be squeezed and trapped by interfacial forces. On the one hand, blisters are undesirable in 2D material devices as they impede charge/photon/phonon transport across the interface, so various means were developed to eliminate interfacial blisters. On the other hand, mechanics analys

Dear iMechanicians,

I want to share our recent work published in Nano Letters on the blister test of nanoflakes. The title, abstract, and links for data are as follows:

Pull-to-Peel of Two-Dimensional Materials for the Simultaneous Determination of Elasticity and Adhesion 

Zheng Fang, Zhaohe Dai*, Bingjie Wang, Zhongzheng Tian, Chuanli Yu, Qing Chen, and Xianlong Wei*

Pectin’s unique physicochemical properties have been linked to a variety of reparative and regenerative processes in nature. To investigate the effect of water on pectin repair, we used a 5 mm stainless-steel uniaxial load to fracture glass phase pectin films. The fractured gel phase films were placed on a 1.5–1.8 mm thick layer of water and incubated for 8 h at room temperature and ambient humidity. There was no immersion or agitation. The repaired pectin film was subsequently assessed for its optical and mechanical properties.

https://twitter.com/stephanebordas/status/1368289311523827714 The University of Luxembourg (UL) invites applications for two PhD Fellow (Doctoral Candidate) positions (m/f) as part of the QuaC project funded by the FNR CORE funding instrument https://www.fnr.lu/funding-instruments/core/

Dear fellow iMechanicians,

Here is our recent paper published in EML on novel anti-icing materials based on propylene-glycol (PG) gels. This work was performed in collaboration with Xi Yao, Baohong Chen and myself while working in Zhigang Suo's lab at Harvard, and provides new solutions for anti-icing purposes (i.e. throug blankets design) without large and costly release of PG in the environment.

Anti-icing propylene glycol materials

Xi Yao, Baohong Chen, Xavier P. Morelle and Zhigang Suo*

M. Ciavarella (2021) Improved Muller approximate solution of the pull-off of a sphere from a viscoelastic substrate, Journal of Adhesion Science and Technology, DOI: 10.1080/01694243.2021.1882766

See also in attach the PDF.

dear collegues 

Static friction at fractal interfaces

https://doi.org/10.1016/j.triboint.2015.09.016

Just submitted a paper on electroadhesion of rough surfaces, greatly simplifying the recent theory of the great Bo Persson , with hot application to touch screens :  see here. 

Comments welcome.

The School of Engineering and Applied Science at the University of Pennsylvania invites applications for two full-time Postdoctoral Researcher positions in the laboratories of Prof. D.S. Srolovitz (https://www.seas.upenn.edu/directory/profile.php?ID=180) and Prof. Robert W. Carpick (http://carpick.seas.upenn.edu).

I attach a Letter I sent to the Editor of a tribology journal, concerning adhesion of rough surfaces. 

I contend that some "criteria" that have been proposed based on extrapolation of numerical results are due to the limitations in present numerical sophisticated rough contact simulations, which only span at most 3 orders of magnitude of wavelengths, so typically people simulate from nanometer to micrometer scale.

Full text here

Wenjie Xia, Xin Qin, Yao Zhang, Rober Sinko, Sinan Keten

Macromolecules (2018), https://pubs.acs.org/doi/abs/10.1021/acs.macromol.8b02243

Journal of The Royal Society Interface 16(151), February 2019.    DOI: 10.1098/rsif.2018.0738

Michele Ciavarella Junki Joe Junki Joe Antonio Papangelo James Richard Barber

In this paper, we experimentally characterize a simple and unified power law for the profiles of a variety of nanobubbles and nanotents formed by 2D materials such as graphene and MoS2 layers. https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.121.266101

ABSTRACT

In this paper, we introduce a new simple yet effective strategy to form "hydrogel skins" on polymer-based medical devices with arbitrary shapes. Hydrogel skins can convert any surface of polymer devices into robust, wet, soft, slippery, antifouling, and ionically conductive without affecting the original properties and geometries.

Abstract