Soft-tribology: Lubrication in a compliant PDMS–PDMS contact

Bongaerts, J.H.H.; Fourtouni, K.; Stokes, Jason R.

doi:10.1016/j.triboint.2007.01.007

Cited by 299 publications

(254 citation statements)

References 19 publications

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“…A base and a curing agent with mass ratio of 10:1 were used for all PDMS samples. The Young's modulus and Poisson's ratio of unmodified Sylgard 184 has been reported to be 2.2 MPa [18] and 0.49 [19] respectively which lies within the range of reported elasticity for human skin of 1-4 MPa. [20] Using a Dynamic Mechanical Analysis (DMA) technique [21] the Young's modulus of all PDMS samples used was found to be 2.7 MPa with a loss tangent, tan δ, of 0.11 for the test conditions employed.…”

Section: Contacting Surfacessupporting

confidence: 68%

Particulate lubricants in cosmetic applications

Timm

Myant

Spikes

et al. 2011

Tribology International

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Polymer powders are commonly added to cosmetic formulations to improve product performance and skin feel. This study investigates the effect of particle concentration and size on the lubricating properties of powder suspensions. Results are reported for various particle sizes and concentrations.When the tribological contact was fully immersed the addition of particles had no effect.However different behaviour was observed when the contact was only partially-lubricated. In this case, a three stage friction coefficient curve was observed. By varying the particle size and concentration it was shown that the duration and magnitude of each stage can be controlled.

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Section: Contacting Surfacessupporting

confidence: 68%

Particulate lubricants in cosmetic applications

Timm

Myant

Spikes

et al. 2011

Tribology International

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“…Finger Ridges Figure 10 -"Liquid bridges" formed at the finger pad/surface interface according to the theory proposed by Dinç et al [13] There have been several studies examining the lubrication of a steel ball sliding and rolling on a soft elastomer surface [26][27][28]. However, while in some cases the Young's modulus of the surface is comparable to the skin of the finger, in many cases the diameter of the ball is too small to represent a finger pad contact area for instance.…”

Section: "Liquid Bridges"mentioning

confidence: 99%

“…A current literature search did not find a Stribeck Curve applicable to the finger. However, some previous studies [26][27][28]14] have indicated that when considering the lubrication of the finger, there are three regimes of lubrication; boundary lubrication, mixed regime lubrication and isoviscous elastohydrodynamic lubrication (IEHL). IEHL is applicable to both 'hard' and 'soft' contact surfaces where there is significant elastic deformation, but this does not increase the lubricant viscosity [26] (or put another way in IEHL it is assumed that any viscosity dependency on pressure is negligible).…”

Section: "Liquid Bridges"mentioning

confidence: 99%

Understanding the Friction Mechanisms Between the Human Finger and Flat Contacting Surfaces in Moist Conditions

et al. 2010

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Human hands sweat in different circumstances and the presence of sweat can alter the friction between the hand and contacting surface. It is therefore important to understand how hand moisture varies between people, during different activities and the effect of this on friction.In this study a survey of fingertip moisture was done. Friction tests were then carried out to investigate the effect of moisture.Moisture was added to the surface of the finger, the finger was soaked in water, and water was added to the counter-surface; the friction of the contact was then measured. It was found that the friction increased, up until a certain level of moisture and then decreased. The increase in friction has previously been explained by viscous shearing, water absorption and capillary adhesion. The results from the experiments enabled the mechanisms to be investigated analytically. This study found that water absorption is the principle mechanism responsible for the increase in friction, followed by capillary adhesion, although it was not conclusively proved that this contributes significantly. Both these mechanisms increase friction by increasing the area of contact and therefore adhesion. Viscous shearing in the liquid bridges has negligible effect. There are, however, many limitations in the modelling that need further exploration.

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“…However, only during the past decade have researchers attempted to quantify oral lubrication using soft-tribology as an in vitro technique, where elastomeric surfaces (e.g. polydimethylsiloxane, PDMS) are typically employed to mimic the low pressure contact between compliant oral surfaces (Bongaerts, Fourtouni, & Stokes, 2007). Lubrication behavior is inherently dependent on relative motion between the soft-contacts of the tribometer, which is classically presented as a Stribeck curve with three different regimes namely boundary, mixed and hydrodynamic lubrication.…”

Section: Introductionmentioning

confidence: 99%

Tribology of swollen starch granule suspensions from maize and potato

Zhang

Selway

Shelat

et al. 2017

Carbohydrate Polymers

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This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.1 | P a g e Highlights  tribology and rheology properties of cooked swollen starch granules (ghosts) characterised  maize granule ghost suspensions reduce friction compared to water  bell-shaped tribology curves due to particle entrainment for maize granule ghosts  limited friction reduction for potato ghosts due to break-up under tribological contact  potato granule ghost suspensions also break up under steady shear 2 | P a g e AbstractThe tribological properties of suspensions of cooked swollen starch granules are characterised for systems based on maize starch and potato starch. These systems are known as granule 'ghosts' due to the release (and removal) of polymer from their structure during cooking. Maize starch ghosts are less swollen than potato starch ghosts, resulting in a higher packing concentration and greater mechanical stability. In a soft-tribological contact, maize ghost suspensions reduce friction compared to the solvent (water), generate bell-shaped tribological profiles characteristic of particle entrainment and show a marked concentration dependence, whereas potato ghost suspensions exhibit lubrication behaviour similar to water. Microscopy analysis of the samples following tribological testing suggests that this is due to the rapid break-up of potato ghosts under the shear and rolling conditions within the tribological contact. A reduction in the small deformation moduli (associated with a weak gel structure) is also observed when the potato ghost suspensions are subjected to steady shear using parallel plate rheometry; both microscopy and particle size analysis show that this is accompanied by the partial shear-induced breakage of ghost particles. This interplay between particle microstructure and the resultant rheological and lubrication dynamics of starch ghost suspensions contributes to an enhanced mechanistic understanding of textural and other functional properties of cooked starches in food and other applications.

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Soft-tribology: Lubrication in a compliant PDMS–PDMS contact

Cited by 299 publications

References 19 publications

Particulate lubricants in cosmetic applications

Particulate lubricants in cosmetic applications

Understanding the Friction Mechanisms Between the Human Finger and Flat Contacting Surfaces in Moist Conditions

Tribology of swollen starch granule suspensions from maize and potato

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