Liquid Crystals in Biotribology

Ermakov, S. F.; Белецкий, А В; Eismont, Oleg; Николаев, В. И.

doi:10.1007/978-3-319-20349-2

Cited by 21 publications

(5 citation statements)

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“…To explain these observations, we further analyzed the formed constructs and determined that hydrophobic reactions and hydrogen bonding in these structures may be substituted, or ‘penetrated’, by other reactions of the same kind, namely, between HA and PL. Penetration of normal constructs by PL was found to be possible, as presented in Figure 12 , yet such penetration requires a very high PL concentration which occurs in the boundary lubrication zone, similar to the structures found in [ 22 ]. Because boundary lubrication regimes are typically when the superficial active phospholipid layer can act as a sacrificial layer for certain perturbation conditions, additional modeling is required to evaluate this unique situation and the various hysteresis effects of advancing and retreating lamellar and transitional bilayer structures, which is beyond the scope of this study.…”

Section: Discussionsupporting

confidence: 63%

Anomalous Behavior of Hyaluronan Crosslinking Due to the Presence of Excess Phospholipids in the Articular Cartilage System of Osteoarthritis

Bełdowski

Weber

Andrysiak

et al. 2017

IJMS

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Lubrication of articular cartilage is a complex multiscale phenomenon in synovial joint organ systems. In these systems, synovial fluid properties result from synergistic interactions between a variety of molecular constituent. Two molecular classes in particular are of importance in understanding lubrication mechanisms: hyaluronic acid and phospholipids. The purpose of this study is to evaluate interactions between hyaluronic acid and phospholipids at various functionality levels during normal and pathological synovial fluid conditions. Molecular dynamic simulations of hyaluronic acid and phospholipids complexes were performed with the concentration of hyaluronic acid set at a constant value for two organizational forms, extended (normal) and coiled (pathologic). The results demonstrated that phospholipids affect the crosslinking mechanisms of hyaluronic acid significantly and the influence is higher during pathological conditions. During normal conditions, hyaluronic acid and phospholipid interactions seem to have no competing mechanism to that of the interaction between hyaluronic acid to hyaluronic acid. On the other hand, the structures formed under pathologic conditions were highly affected by phospholipid concentration.

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Section: Discussionsupporting

confidence: 63%

Anomalous Behavior of Hyaluronan Crosslinking Due to the Presence of Excess Phospholipids in the Articular Cartilage System of Osteoarthritis

Bełdowski

Weber

Andrysiak

et al. 2017

IJMS

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“…-(i) the thickness [48] and orientation [49] of grafted molecules at the macro- [50] and nanoscale [51]: That means that the CPD continuously increases with the packing density of SAM [52] ; -(ii) the grafting success [53]: the larger the CPD difference vs. the reference bias (CPD Si = 0 V), the stronger the molecules adhere onto the silicon substrate; -(iii) the surface reactivity for a given surface [44]: the more negative of the CPD measurement the higher the surface reactivity, according to the reactivity of the reference. In our case, any positive rise of the CPD may be connected to a decrease of the surface reactivity vs. the bare silicon one [45]; -(iv) many other tribological properties as friction level or wear precursors detection in the sub-surfaces as reported by several authors [54,55], thus: Figure 4 compares the CPD of the three printed nanopatterned SAM samples with respect to the bare silicon one taken as the reference with 0 V bias:…”

Section: Kelvin Probe Analysissupporting

confidence: 51%

Thermal-Controlled Frictional Behaviour of Nanopatterned Self-assembled Monolayers as Triboactive Surfaces

et al. 2020

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Friction is an important limitation of energy efficiency performances of MEMS/NEMS but is, in the same time, a great opportunity for harvesting energy by designing optimized Tribo-Electric Nano-Generators (TENG). Thus, frictional behaviour can be accurately controlled in real-time by using thermally sensitive periodic patterned self-assembled monolayers of n-octadecyltrichlorosilane (OTS) grafted on MEMS surfaces. Nanopatterns are currently used in order to limit the wear rate without modifying the frictional behaviour. In this work, patterns have been created by micro-contact printing (µCP) using a polydimethylsiloxane (PDMS) stamp displaying a trapezoidal profile. Hence pattern periodicity can be continuously changed-and then optimized from discontinuous to pseudo-continuous-by applying a controlled normal load on the soft PDMS stamp. A multiscale tribological study has been carried out on these nano-patterns by using both single-asperity and multi-asperity nanotribometers. Lateral Force Microscopy (LFM) provides the individual frictional behaviour of each pattern's component whereas the multiasperity nanotribometer rather gives the emerging frictional behaviour induced by the patterning according to temperature. As a macroscopic crucial parameter while designing TENG's devices, this macroscopic behavior has to be carefully optimized for each practical applications at the molecular scale. Thus, whereas the microscale frictional behaviour can be precisely optimized by the pattern's periodicity, the macroscopic one can be accurately controlled with values of friction coefficient ranging from 0.12 to 0.04 by varying the contact temperature. In addition, any inertial effects observed in the thermal-controlled frictional behavior of nano-patterns can be drastically reduced using infra-red emission as thermal source.

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“…This lipid response is expected to improve their resistance to the high shear and compression forces experienced in human joints while still maintaining their hydrated lubricating properties. The water expelled during confinement may also play a role in the lubrication, synergistically with the transfer of fluid between the cartilage and synovial fluid which is believed to occur during joint lubrication [58]. Understanding of the hydration and structural changes of the PC lipids under uniaxial stress is the first step toward fully understanding how their structure is changed in dynamic, lubricating joints and how the act to improve the lubricating properties of synovial fluid.…”

Section: Discussionmentioning

confidence: 99%

Structural Evidence for a Reinforcing Response and Retention of Hydration During Confinement of Cartilage Lipids

et al. 2021

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Lipids have an important role in the complex lubrication of articulating joints, however changes in lipid phase behavior that occur owing to mechanical confinement are not well understood. Here, a surface force-type apparatus has been combined with neutron reflectometry to measure confinement-induced changes in the structure of lipids, the major surface-active component of the lubricant in articulating joints. The same incompressible state was accessed under low uniaxial stress (1 bar), irrespective of whether the lipids had started out unconfined above or below the Lα phase transition, and irrespective of whether they were fully or partially hydrated. In this incompressible state, the lipid component had thickened indicating extension and rearrangement of the lipid chains in response to the applied stress. The small amount of water remaining between each lipid bilayer was found to be similar for all chain lengths and starting phases. This represents the first structural evidence of the tightly bound water layer at the headgroups, which is required for hydration lubrication under load.

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Liquid Crystals in Biotribology

Cited by 21 publications

References 0 publications

Anomalous Behavior of Hyaluronan Crosslinking Due to the Presence of Excess Phospholipids in the Articular Cartilage System of Osteoarthritis

Anomalous Behavior of Hyaluronan Crosslinking Due to the Presence of Excess Phospholipids in the Articular Cartilage System of Osteoarthritis

Thermal-Controlled Frictional Behaviour of Nanopatterned Self-assembled Monolayers as Triboactive Surfaces

Structural Evidence for a Reinforcing Response and Retention of Hydration During Confinement of Cartilage Lipids

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