New SFA Techniques for Studying Surface Forces and Thin Film Patterns Induced by Electric Fields
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- 作者：Hongbo Zeng ; Yu Tian ; Travers H. Anderson ; Matthew Tirrell ; Jacob N. Israelachvili
- 刊名：Langmuir
- 出版年：2008
- 出版时间：February 19, 2008
- 年：2008
- 卷：24
- 期：4
- 页码：1173 - 1182
- 全文大小：1277K
- 年卷期：v.24,no.4(February 19, 2008)
- ISSN：1520-5827
文摘
We describe two ways to measure normal and/or lateral forces between two surfaces in a surface forces apparatus(SFA) while an electric field is applied between the surfaces. The first method involves depositing thin conductivelayers on the exposed substrate (usually mica) sheets; the second involves using the optically reflecting silver layerson the back surfaces of the sheets as the electrodes. Two types of experiments were performed using these newtechniques: (1) measuring the effects of an electric field on the rheology of an ~40-
m-thick film of zeolite particlessuspended in silicone oil and (2) a dynamic study of electric field-induced pattern formation of a thin polymer film.In the first study, under an electric field of strength ~106 V/m the shear force or effective viscosity of the colloidsuspension was found to be two orders of magnitude higher than in the absence of the field, when the expected bulkvalue was measured. In the dynamic study, the initially uniform film transformed into a 2-D honeycombed networkof depressed cells bounded by elevated ridges that grew slowly with time in a way consistent with previously derivedtheories. The new techniques should be applicable to studies of other systems and interactions, such as double-layerforces, micro- and nanoelectrorheology, electric field-induced ordering of particles, and the effects of electric fieldson adhesion, friction, and lubrication.
m-thick film of zeolite particlessuspended in silicone oil and (2) a dynamic study of electric field-induced pattern formation of a thin polymer film.In the first study, under an electric field of strength ~106 V/m the shear force or effective viscosity of the colloidsuspension was found to be two orders of magnitude higher than in the absence of the field, when the expected bulkvalue was measured. In the dynamic study, the initially uniform film transformed into a 2-D honeycombed networkof depressed cells bounded by elevated ridges that grew slowly with time in a way consistent with previously derivedtheories. The new techniques should be applicable to studies of other systems and interactions, such as double-layerforces, micro- and nanoelectrorheology, electric field-induced ordering of particles, and the effects of electric fieldson adhesion, friction, and lubrication.