2004 Fiscal Year Final Research Report Summary
A study on texture change on Langmuir monolayrs by optical tweezers
| Project/Area Number |
15360015
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Thin film/Surface and interfacial physical properties
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| Research Institution | Hokkaido University |
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Principal Investigator |
HATTA Eiji Hokkaido University, Grad.School of Information.Sci and Tech., Instructor, 大学院・情報科学研究科, 助手 (90238022)
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| Project Period (FY) |
2003 – 2004
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| Keywords | Brewster angle microscopy / Langmuir monolayers / optical tweezers / disclination / texture / molecular orientation / line tension / orientational elasticity |
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| Research Abstract |
The combined system of Brewster angle microscope with optical tweezers has been constructed. Integer s=1 point disclination textures of the molecular orientation of a pentacosadiynoic acid Langmuir monolayr split into two s=1/2 defects upon laser heating. We explain this behavior by a competition of the line tension of a π-wall of the c-director connecting both defects with the continuum orientation elastic energy. While the line tension causes an attraction, the orientation elastic energy mediates a repulsive interaction between the half-integer disclinations. Laser heating of the texture locally induces an anisotropic stress in the orientationally ordered solid phase, forcing the molecular orientation into the monolayr plane and there by reducing the π-wall line tension. The static and dynamic string defect textures connecting pairs of half-integer disclinations have been observed by Brewster angle microscopy in the solid phase of pentacosadiynoic acid Langmuir monolayers. The static string defect structures have appeared coexisting with two kinds of point disclinations that have four and two black brushes. The use of local laser heating has allowed one to observe kinetics of creation and annihilation of string defects connecting the two-half-integer disclinations in the splitting process of an s=1 point disclination into fractional disclinations. These kinetics have been analyzed by studying the competition between the orientational elasticity of the molecules and the line tension of the string and the drag force of the disclinations. The above results demonstrate that optical tweezers are a powerful tool for the study of micromanipulations and microrheology in the solid Langmuir monolayrs.
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Research Products
(4 results)
