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Structural aging and stiction dynamics in confined liquid films
1Tokyo Research Laboratories, Kao Corporation, 2-1-3 Bunka, Sumida-ku, Tokyo 131-8501, Japan. yamada.s@kao.co.jp
The Journal of Chemical Physics
|November 18, 2009
Summary
Static friction in thin films of 1,3-dimethylbutyl octyl ether (DBOE) shows reversible solid-liquid transitions. The study observed matching fast time constants for stopping and starting, indicating a glass-like behavior under pressure.
Area of Science:
- Materials Science
- Tribology
- Soft Matter Physics
Background:
- Static friction, or stiction, is a critical phenomenon in micro/nanoscale devices.
- Understanding stiction dynamics in molecularly thin films is essential for predicting device performance and longevity.
- Irregularly shaped molecules present unique challenges in modeling confined film behavior.
Purpose of the Study:
- To investigate the static friction (stiction) of molecularly thin films of 1,3-dimethylbutyl octyl ether (DBOE) confined between mica surfaces.
- To characterize the stop-start dynamics and identify relaxation processes governing stiction.
- To explore the influence of aging time and applied pressure on stiction behavior.
Main Methods:
- Utilized the surface forces apparatus (SFA) to perform stop-start experiments on DBOE films.
- Measured stiction spike as a function of surface stopping time (t) and applied pressure (P).
- Analyzed relaxation processes using double exponential fits to determine time constants.
Main Results:
- Observed two distinct relaxation processes during stopping and starting, each with fast and slow time constants.
- Identified a characteristic nucleation time (tau(n)) below which no stiction spike occurs.
- Found that the fast time constant on starting (tau(1)) closely matches the fast time constant on stopping (tau(n)), suggesting a reversible transition.
- Demonstrated an exponential dependence of fast time constants on pressure, implying a glass-like transition.
Conclusions:
- The study provides the first direct observation of matching stopping and starting time constants in stiction dynamics, indicative of a reversible solid-liquid transition.
- The pressure dependence suggests a glass-like nature for this transition in DBOE films.
- Compared to stick-slip friction, DBOE exhibits different solid-liquid transition dynamics, with stiction showing a reversible transition and stick-slip friction a discontinuous one.
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