Lubrication at Physiological Pressures by Polyzwitterionic Brushes
Meng Chen,1*
Wuge H. Briscoe,1
Steven P. Armes,2
Jacob Klein1,3
The very low sliding friction at natural synovial joints, which
have friction coefficients of µ < 0.002 at pressures
up to 5 megapascals or more, has to date not been attained in
any human-made joints or between model surfaces in aqueous environments.
We found that surfaces in water bearing polyzwitterionic brushes
that were polymerized directly from the surface can have µ
values as low as 0.0004 at pressures as high as 7.5 megapascals.
This extreme lubrication is attributed primarily to the strong
hydration of the phosphorylcholine-like monomers that make up
the robustly attached brushes, and may have relevance to a wide
range of human-made aqueous lubrication situations.
2 Department of Chemistry, University of Sheffield, Sheffield S3 7HF, UK.
3 Weizmann Institute, Rehovot 76100, Israel.
* Present address: Procter and Gamble (Beijing) Technical Centre, Floor 5-8, Tongfang Building, 18 Shuangqing Road, Haidian District, Beijing 100084, People's Republic of China.
Present address: School of Chemistry, University of Bristol, Bristol BS8 1TS, UK.
To whom correspondence should be addressed. E-mail: jacob.klein{at}weizmann.ac.il
