Stick-slip friction and wear of articular joints

Lee, Dong Woog; Banquy, Xavier; Israelachvili, Jacob N.

doi:10.1073/pnas.1222470110

Cited by 98 publications

(77 citation statements)

References 47 publications

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“…The surfaces prepared as above were mounted in an SFA 2000 (ref. 34) attached with semiconductive strain gauges at double cantilever springs for load measurement 35 . Both surfaces were kept immersed in treatment buffer (pH 3 sodium acetate or pH 7 phosphate) using a miniaturized 'cup' , which contains buffer reservoir (Fig.…”

Section: Methodsmentioning

confidence: 99%

Surface-initiated self-healing of polymers in aqueous media

et al. 2014

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Polymeric materials that intrinsically heal at damage sites under wet or moist conditions are urgently needed for biomedical and environmental applications [1][2][3][4][5][6] . Although hydrogels with self-mending properties have been engineered by means of mussel-inspired metal-chelating catechol-functionalized polymer networks 7-10 , biological self-healing in wet conditions, as occurs in self-assembled holdfast proteins in mussels and other marine organisms 11,12 , is generally thought to involve more than reversible metal chelates. Here we demonstrate self-mending in metal-free water of synthetic polyacrylate and polymethacrylate materials that are surface-functionalized with mussel-inspired catechols. Wet self-mending of scission in these polymers is initiated and accelerated by hydrogen bonding between interfacial catechol moieties, and consolidated by the recruitment of other non-covalent interactions contributed by subsurface moieties. The repaired and pristine samples show similar mechanical properties, suggesting that the triggering of complete self-healing is enabled underwater by the formation of extensive catechol-mediated interfacial hydrogen bonds.All polymeric materials suffer damage in the course of their functional lifetimes. Few, if any, completely heal at damage sites. Despite recent progress in the design of self-mending polymeric materials based on crack-activated crosslinking 1 , light 2 , heat 3 or other external stimuli 4 , these remain less than perfectly healed, and, in the case of polymers in wet environments, self-healing technologies are even more limited than those engineered for dry conditions. Mussel adhesive holdfasts exhibit significant self-healing capabilities 11,12 , although the molecular mechanisms involved are poorly understood. Notwithstanding this, the selfmending adhesion and cohesion of isolated dopa (3,4-dihydroxyphenyl-L-alanine)-containing adhesive proteins were shown to rely critically on maintaining dopa in an acidic and reducing environment 13,14 . Significantly different conditions are required to recapitulate the self-healing cohesion of tris-dopa-Fe 3+ -mediated complexes in proteins and polymers [7][8][9]15 . Such results increasingly suggest the importance of dopa, but also its subtle and diverse interfacial reactivity vis-à-vis the traditional and still widely held view that dopa, and catechols generally, function primarily as crosslinkers after their 2-electron oxidation to quinones 16 . To better assess the contribution of catechol to polymer selfhealing in a reducing (pH 3), metal-free wet environment, we prepared a material from common, water-insoluble synthetic acrylic polymers having a catechol-functionalized surface. These materials are completely self-healing in a process initiated by catecholmediated interfacial hydrogen bonding, and consolidated by followup interactions (for example, hydrophobic and steric) after a brief compression (∼6 × 10 4 Pa). The crucial and robust roles played by

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Section: Methodsmentioning

confidence: 99%

Surface-initiated self-healing of polymers in aqueous media

et al. 2014

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“…An important step towards bridging this gap was taken by Israelachvili et al who measured the friction forces between cartilage surfaces mounted on a Surface Forces Apparatus, SFA. 15 …”

Section: Introductionmentioning

confidence: 99%

Synergies in lubrication

Dédinaité

Claesson

2017

Phys. Chem. Chem. Phys.

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To slide surfaces against each other with application of a minimum force and minimum wear has been important since ancient times, and it remains equally important today. The use of oil-soluble lubricants is widely spread in technology, whereas living organisms have developed water-soluble lubricants to facilitate sliding motions. In this perspective article we focus on water-based lubrication in the boundary lubrication regime, and particularly lubrication synergies. This focus has, of course, found inspiration from the outstanding lubrication properties of synovial joints. It has ignited significant amount of research, mostly aimed at answering the question: Which molecule is the magic biolubricant? Different research groups have advocated different answers, and the debate has been intensive. In this article we argue that the question in itself is inappropriate. The relevant question is rather the following: How do molecules work in synergy to provide superior lubrication?

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“…It has been used not only to measure normal adhesion forces (Lee et al, 2014), but also lateral friction forces (Lee, Banquy, & Israelachvili, 2013). Recently, pH-and contact time-dependent interactions of chitosan (Mw ∼ 150 kDa) were measured with an SFA (Lee, Lim, Israelachvili, & Hwang, 2013).…”

Section: Introductionmentioning

confidence: 99%

Contact time- and pH-dependent adhesion and cohesion of low molecular weight chitosan coated surfaces

Lim

Lee

Israelachvili

et al. 2015

Carbohydrate Polymers

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a b s t r a c tLow molecular weight chitosan (LMW chitosan, ∼5 kDa) potentially has many desirable biomedical applications such as anti-microbial, anti-tumor, and anti-diabetes. Unlike high molecular weight chitosan, LMW chitosan is easily dissolvable in aqueous solutions even at neutral and basic pH, but its dissolution mechanism is not well understood. Here, we measured adhesion and cohesion of molecularly thin LMW chitosan films in aqueous solutions in different buffer pHs (from 3.0 to 8.5) using a surface forces apparatus (SFA). Interestingly, significantly lower adhesion force was measured for LMW chitosan films compared to the high molecular weight chitosan (∼150 kDa) films. Not only the strength of adhesion is lower, but also the critical contact time where adhesion starts to increase with contact time is longer. The results from both the SFA and atomic force microscopy (AFM) indicate that, in physiological and basic conditions, the low cohesion of LMW chitosan due to the stiffness of the chain which cause strong electrostatic correlation energy penalty when they are aggregated. Here, we propose the reduction in cohesion for shorter chitosan (LMW chitosan) as an explanation of its high solubility of LMW chitosan in physiological pHs.

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Stick-slip friction and wear of articular joints

Cited by 98 publications

References 47 publications

Surface-initiated self-healing of polymers in aqueous media

Surface-initiated self-healing of polymers in aqueous media

Synergies in lubrication

Contact time- and pH-dependent adhesion and cohesion of low molecular weight chitosan coated surfaces

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