NANOTECHNOLOGY
Current Research - CONTROL OF FRICTION AT THE NANOSCALE
Ability to control and manipulate friction during sliding is of significant importance for a large variety of technological applications. The outstanding challenge deals with complex dynamical systems with many degrees of freedom, under strict size confinement, and having only very limited control access. Despite great progress made through the past half century, many basic issues in fundamental tribology such as origin of friction and failure of lubrication have remained unsolved. Moreover, the current reliable knowledge related to friction and lubrication is mainly applicable to the macroscopic systems and machinery and, most likely, will be of only of limited use (if any at all) for micro- and nano-systems. Indeed, when the thickness of the lubrication film is of the same order as the molecular or atomic size, the behavior of the lubricant becomes significantly different from the behavior of macroscopic (bulk) lubricant.
Better understanding of the intimate mechanisms of friction, lubrication, and other interfacial phenomena at the atomic and molecular scales is expected to provide designers and engineers the required tools and capabilities to control and monitor friction, reduce unnecessary wear, and predict mechanical faults and failure of lubrication in MEMS and nano-devices.
In addition to conventional dissipation mechanisms (e.g., photonic and electronic), friction of the nonlinear system can be significantly affected by the dynamical properties of the sliding system such as, for example, the fluctuations of each individual element from the center of mass motion. A nonlinear system driven far from equilibrium can exhibit a variety of complex spatial and temporal behaviors, each resulting in different patterns of motion and corresponding to different friction coefficients.
Achievements
In our research, we address some fundamental issues related to targeting and control of friction in small driven nonlinear particle arrays. Recently, we proposed a feedback control scheme, based on the properties of terminal attractors. This type of control has been successfully implemented in modifying the dynamical behavior of artificial neural networks. The main advantage of terminal attractor algorithms consists in their robustness and ability to significantly reduce the transient times (we will later on discuss the properties of terminal attractors).
CESAR: Y. Braiman,(Principal Investigator) J. Barhen, V. Protopopescu, and T. Thundat
External Collaborators: P. Cummings (UTK/ORNL) and S.Granick (UIUC)
Performance of the algorithm:
(Click figures for larger view)
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- Y. Braiman, F. Family, H. G. E. Hentschel, "Array Enhanced Friction in the Periodic Stick-Slip Motion of Nonlinear Oscillators", Phys. Rev. E 53, R3005 (1996).
- Y. Braiman, F. Family, H. G. E. Hentschel, "Nonlinear Friction in the Periodic Stick-Slip Motion of Coupled Oscillators in Periodic Potential", Phys. Rev. B15, 55, 5491 (1997).
- Y. Braiman, H. G. E. Hentschel, F. Family, C. Mak, and J. Krim, "Tuning Friction with Noise and Disorder", Phys. Rev. E 59, R4737 (1999).
- H. G. E. Hentschel, F. Family, and Y. Braiman, "Friction Selection in Nonlinear Particle Arrays", Phys. Rev. Lett. 83, 104 (1999).
- F. Family, H. G. E. Hentschel, and Y. Braiman, "Friction at the Nanoscale", J. Chem. Phys. B 104, 3984 (2000).
- Y. Braiman, J. Barhen, and V. Protopopescu, "Terminal Attractor Control of Friction at the Nanoscale", submitted for publication (2002).
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