Biolubrication and Biomimetic Lubrication

A special issue of Lubricants (ISSN 2075-4442).

Deadline for manuscript submissions: closed (10 November 2017) | Viewed by 27345

Special Issue Editor


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Guest Editor
Department of Mechanical Engineering, Technical University of Denmark, DK-2800 Kgs. Lyngby, Denmark
Interests: biotribology; surface functionalization; solid/liquid interface; implants

Special Issue Information

Dear Colleagues,

Lubricating behavior of biological systems has been a long-standing subject for tribologists in both academic and practical point of views. Fundamentally, the lubrication mechanisms of biotribosystems, e.g., synovial joints, are unique and complex and they cannot be fully explained with the theories established by engineering tribology. Biolubrication is achieved mostly with water and displays life-long service, although water is generally excluded as lubricant in man-made engineering systems. Practically, retarded or failed lubricating functions in biological systems may lead to severe human diseases, for instance arthritis, xerostomia, and xerophthalmia. Thus, understanding the lubricating function of biological systems is of vital importance for human health. Continued and broadened interests in biotribology in recent years extended its scope from wet systems, such as synovial joints, eyes, and gastrointestinal tracts, to dry systems, such as skin and hair.

Biomimetic lubrication is relatively new concept and approach. It began with the general development and progress of biomimicry of other science and engineering disciplines from a couple of decades ago, and is based on the assumption that nature may provide useful hints in designing the structure and functionalities of engineering systems. Tribology is an excellent domain to apply this approach, as it is a representative multidisciplinary science and engineering. Since biolubrication is most clearly distinguished from engineering tribosystems in terms of base stock, i.e., water instead of oils; first efforts in the past a couple of decades have been focused on the development and characterization of water-compatible additives, including polymers, surfactants, ionic liquids, inorganic nanoparticles, and various carbon-based nano-objects. For this reason, biomimetic lubrication is often considered synonymous with “water-based lubrication”. However, the scope of biomimetic lubrication can be much broader, as the uniqueness is not limited to its common base stock, but also its mechanisms, e.g., self-healing abilities, facile adaption to environment, and involvement of multiphase substances in lubrication, to name a few. These features have not been fully mimicked or utilized yet in engineering systems.

We believe that it is timely to review the recent progress of biolubrciation and biomimetic lubrication and discuss about the direction of future researches on this field. We would like to invite papers on recent research activities and progress on all aspects of biolubrication and biomimetic lubrication to this Special Issue. Researches on both fundamental science and industrial applications are equally valued and both review papers and original research papers on new developments in this field are welcome in this Special Issue.

We are looking forward to your valued contributions.

Prof. Dr. Seunghwan Lee
Guest Editor

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Keywords

  • biolubrication
  • biomimetic
  • bioinspired
  • biotribology
  • aqueous lubrication
  • additives

Published Papers (4 papers)

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Research

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12 pages, 3736 KiB  
Article
Dispersion Stability and Lubrication Performance Correlation of Vegetable Oil-In-Water Emulsions with Nanoparticle-Shielded Oil Droplets
by Reza Taheri, Buyung Kosasih, Hongtao Zhu and Anh Kiet Tieu
Lubricants 2018, 6(2), 55; https://doi.org/10.3390/lubricants6020055 - 09 Jun 2018
Cited by 8 | Viewed by 3909
Abstract
Vegetable oil-in-water (VO/W) emulsions are bio-based metal working lubricants. The emulsions’ lubrication performance depends on the stability of oil droplets. In this paper, the oil droplets’ dispersion stability and lubrication of emulsions containing TiO2/SiO2 nanoparticles (NPs) as dispersant and lubrication [...] Read more.
Vegetable oil-in-water (VO/W) emulsions are bio-based metal working lubricants. The emulsions’ lubrication performance depends on the stability of oil droplets. In this paper, the oil droplets’ dispersion stability and lubrication of emulsions containing TiO2/SiO2 nanoparticles (NPs) as dispersant and lubrication agents have been investigated. Enhanced dispersion of NP-shielded oil droplets was found. Increasing the NPs’ mass fraction initially lowers the average size of NP-shielded droplets up to the saturation of the droplets’ surface with NPs at 0.5 wt % mass fraction. NPs also form NP agglomerates in emulsions, more so after the droplets’ surfaces have been saturated with NPs. There is an apparent minimum quantity of NPs (~0.5 wt %) required to ensure sustained dispersions of the droplets which is thought to be related to the oil concentration and the droplets’ total surface-area-to-volume ratio. Below the required quantity of NPs, partially shielded and fully shielded droplets coexist. The partially shielded droplets initially attract other droplets and undergo limited coalescence but retain their long-term stability. A small quantity of NPs improves the antiwear property of the lubricants. However, emulsions with NPs have slightly higher friction than the NP-free emulsion due to the reduced strength of the tribofilm. Despite the increased friction, the tribofilm formed in presence of NPs can easily be removed from the surface with water, indicating cleaner surfaces after the lubrication (i.e., less oil residue on the surfaces), which, for the sake of cleanliness, is favourable in many applications. Full article
(This article belongs to the Special Issue Biolubrication and Biomimetic Lubrication)
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17 pages, 3653 KiB  
Article
A Preliminary Study to Enhance the Tribological Performance of CoCrMo Alloy by Fibre Laser Remelting for Articular Joint Implant Applications
by Chi-Wai Chan, Graham C. Smith and Seunghwan Lee
Lubricants 2018, 6(1), 24; https://doi.org/10.3390/lubricants6010024 - 02 Mar 2018
Cited by 10 | Viewed by 4043
Abstract
CoCrMo alloy has long been used as a pairing femoral head material for articular joint implant applications because of its biocompatibility and reliable tribological performance. However, friction and wear issues are still present for CoCrMo (metal)/CoCrMo (metal) or CoCrMo (metal)/ultrahigh molecular weight polyethylene [...] Read more.
CoCrMo alloy has long been used as a pairing femoral head material for articular joint implant applications because of its biocompatibility and reliable tribological performance. However, friction and wear issues are still present for CoCrMo (metal)/CoCrMo (metal) or CoCrMo (metal)/ultrahigh molecular weight polyethylene (UHMWPE) (plastic) pairs in clinical observations. The particulate wear debris generated from the worn surfaces of CoCrMo or UHMWPE can pose a severe threat to human tissues, eventually resulting in the failure of implants and the need for revision surgeries. As a result, a further improvement in tribological properties of this alloy is still needed, and it is of great interest to both the implant manufacturers and clinical surgeons. In this study, the surface of CoCrMo alloy was laser-treated by a fibre laser system in an open-air condition (i.e., no gas chamber required). The CoCrMo surfaces before and after laser remelting were analysed and characterised by a range of mechanical tests (i.e., surface roughness measurement and Vickers micro-hardness test) and microstructural analysis (i.e., XRD phase detection). The tribological properties were assessed by pin-on-disk tribometry and dynamic light scattering (DLS). Our results indicate that the laser-treated surfaces demonstrated a friction-reducing effect for all the tribopairs (i.e., CoCrMo against CoCrMo and CoCrMo against UHHMWPE) and enhanced wear resistance for the CoCrMo/CoCrMo pair. Such beneficial effects are chiefly attributable to the presence of the laser-formed hard coating on the surface. Laser remelting possesses several competitive advantages of being a clean, non-contact, fast, highly accurate and automated process compared to other surface coating methods. The promising results of this study point to the possibility that laser remelting can be a practical and effective surface modification technique to further improve the tribological performance of CoCr-based orthopaedic implants. Full article
(This article belongs to the Special Issue Biolubrication and Biomimetic Lubrication)
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15 pages, 5773 KiB  
Article
Phospholipid Vesicles in Media for Tribological Studies against Live Cartilage
by Teresa Veselack, Gregoire Aldebert, Ana-Maria Trunfio-Sfarghiu, Thomas M. Schmid, Michel P. Laurent and Markus A. Wimmer
Lubricants 2018, 6(1), 19; https://doi.org/10.3390/lubricants6010019 - 11 Feb 2018
Cited by 15 | Viewed by 5026
Abstract
Introduction: Pre-clinical testing of hemiarthroplasty devices requires that the tribological conditions present in vivo with live cartilage be closely duplicated. A current limitation in the tribological testing of live cartilage involves the use of cell-culture media as lubricant. Study Aim: to develop and [...] Read more.
Introduction: Pre-clinical testing of hemiarthroplasty devices requires that the tribological conditions present in vivo with live cartilage be closely duplicated. A current limitation in the tribological testing of live cartilage involves the use of cell-culture media as lubricant. Study Aim: to develop and test a new hyaluronan-phospholipid based medium (HA–phospholipid medium) that combines the rheological and frictional properties of synovial fluid with the nourishing properties of culture media to keep cells alive. Materials and Methods: The HA–phospholipid medium consisted of culture medium with added phospholipid dipalmitoylphosphatidylcholine (0.3 mg/mL), and hyaluronic acid (2.42 mg/mL). A standard cell culture medium was used as the control. The rheology of each medium was determined using a flat plate configuration. Bovine calf cartilage was used to assess cell viability and friction in each medium. For friction measurements, a cobalt-chrome alloy ball was articulated against cartilage disks immersed in medium. Results: Lipid vesicles 0.1 to 50 μm in diameter were identified in the HA–phospholipid medium. Cartilage cell viability was significantly higher in the HA–phospholipid medium (62% ± 8%, 95% CI) than in control medium (49.5% ± 5%) (p = 0.009). The HA–phospholipid medium exhibited strong shear-thinning behavior, similar to synovial fluid, with viscosities ~100-fold higher at 10 s−1 and 5-fold higher at 20,000 s−1 than the approximately Newtonian control medium. The HA–phospholipid medium also yielded 20% lower friction values than the control medium after one hour of testing. Conclusions: The rheological and friction results indicate that the HA–phospholipid medium is superior to the control cell culture medium in emulating the shear thinning and lubricative properties of natural synovial fluid, making it more clinically relevant for in vitro wear and friction testing with live cartilage. Full article
(This article belongs to the Special Issue Biolubrication and Biomimetic Lubrication)
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Review

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26 pages, 81187 KiB  
Review
Advances in Tribology of Lubricin and Lubricin-Like Synthetic Polymer Nanostructures
by Ilker S. Bayer
Lubricants 2018, 6(2), 30; https://doi.org/10.3390/lubricants6020030 - 04 Apr 2018
Cited by 25 | Viewed by 13543
Abstract
Articular cartilage surrounds the ends of diarthrodial joints (most common movable joints) and during motion, it experiences a wide range of loading conditions while remaining under exceedingly low-friction and wear-free conditions. This remarkable tribological performance stems from complex interactions between the synovial fluid [...] Read more.
Articular cartilage surrounds the ends of diarthrodial joints (most common movable joints) and during motion, it experiences a wide range of loading conditions while remaining under exceedingly low-friction and wear-free conditions. This remarkable tribological performance stems from complex interactions between the synovial fluid and articular cartilage. In fact, lubricin and hyaluronic acid (HA) that are part of the synovial fluid are now known to be the key contributors to effective joint lubrication and wear protection. Studies involving animal models and artificial systems suggest that lubricin and HA molecules may work in tandem to produce a highly synergistic effect for lubrication. However, latest observations suggest that lubricin has significant potential for protecting the articular joints, probably more than HA. Recently, lurbicin-related friction regulation in soft eye tissues, where much lower forces are involved compared to knee joints for instance, has been shown to be related to dry eye disease and contact lens discomfort. As such, lubricin’s role in natural friction regulation is very complex. Moreover, partially unresolved water-lubricin interactions are essential for lubrication and load carrying function in the joints. The chemical structure of lubricin has inspired several chemists to synthesize new copolymers and polymer brushes that function just like lubricin in order to design new synthetic or bio-based lubricants with ultra-low-friction coefficients. Hence, lubricin has emerged as a key natural molecule for bioinspired tribology. The aim of this review is to present the latest advances in understanding of lubricin’s function in joint lubrication and in soft tissue friction (i.e., human eye) and document what has been achieved so far in transforming this biomedical knowledge into new polymer design for advanced engineering tribology. It is hoped that this review will catalyze research and development efforts in obtaining very stable and high load-bearing polymer-based ultra-low-friction surfaces via biomimicry. Full article
(This article belongs to the Special Issue Biolubrication and Biomimetic Lubrication)
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