Share Email Print
cover

Proceedings Paper

Electric-field-induced molecular reorientation dynamics by near-field scanning optical microscopy
Author(s): Daniel A. Higgins; Erwen Mei; Xiangmin Liao
Format Member Price Non-Member Price
PDF $14.40 $18.00

Paper Abstract

A new technique developed in this laboratory and based on near-field scanning optical microscopy (NSOM) is used to study the field-induced reorientation of molecules in local regions of thin film materials. A highly concentrated electric field is applied across the sample, between the metal-coated near-field probe and the sample substrate. Molecular motion induced in the sample by modulation of the electric field is observed using NSOM methods. Lock-in detection of the optical response to a sinusoidally- modulated field, recorded under cross-polarized, transmitted-light conditions allows for the recording of dynamics images. The local rate of reorientation is measured for individual locations in a sample by recording the response in either the time or frequency domains. Dynamics information is obtained with microsecond(s) ec time resolution and nanometer-scale spatial resolution. This method is applied in studies of polymer-dispersed liquid crystal films. In these materials, small droplets of nematic liquid crystal are dispersed in an otherwise uniform poly(vinyl alcohol) film. The liquid crystal droplets are birefringent, forming electrically-switchable light-scattering centers. A simple forced-oscillator model for the reorientation dynamics in the liquid crystal is presented. Variations in the time scale and extent of molecular reorientation are observed as a function of field strength, droplet size, droplet shape, and position probed. The data are interpreted based on knowledge of the important intermolecular forces active in these materials.

Paper Details

Date Published: 17 June 1999
PDF: 10 pages
Proc. SPIE 3607, Scanning and Force Microscopies for Biomedical Applications, (17 June 1999); doi: 10.1117/12.350633
Show Author Affiliations
Daniel A. Higgins, Kansas State Univ. (United States)
Erwen Mei, Kansas State Univ. (United States)
Xiangmin Liao, Kansas State Univ. (United States)


Published in SPIE Proceedings Vol. 3607:
Scanning and Force Microscopies for Biomedical Applications
Eiichi Tamiya; Shuming Nie, Editor(s)

© SPIE. Terms of Use
Back to Top