Liquid-Crystal Displays: Fabrication and Measurement of a Twisted Nematic Liquid-Crystal Cell

Penny S. Hale , Joe G. Shapter and Nico H. Voelcker
School of Chemistry, Physics and Earth Sciences (SoCPES), Flinders University of South Australia, Adelaide, SA 5001, Australia
Michael J. Ford
Institute of Nanoscale Technology, University of Technology, Broadway, NSW, Sydney 2007, Australia
Eric R. Waclawik
School of Physical and Chemical Sciences, Queensland University of Technology, Brisbane, QLD, 4001, Australia
J. Chem. Educ., 2004, 81 (6), p 854
DOI: 10.1021/ed081p854
Publication Date (Web): June 1, 2004

Abstract

This article describes a set of experiments designed to explore some of the basic properties of liquid crystals. The relationship between molecular shape, molecular order, and macroscopic properties, such as optical birefringence, phase transitions, and electrically–controlled birefringence, as demonstrated by the electro–optic effect, are investigated. Students are encouraged to consider the importance of surface phenomena on these properties and how molecular order at a surface can be transferred throughout the bulk of such a highly associated fluid. Experiments are performed using either a sandwich cell or a twist cell containing the aligned nematic liquid crystal 4'-pentyl-4-biphenylcarbonitrile. In the first part, students investigate the anisotropic nature of this liquid crystalline material using the wave-retarding properties of an aligned sample confined within a sandwich cell. In the second part, students manufacture a twisted nematic liquid-crystal cell and characterize the important elements required in a working display device based on electro–optical principles. The experiments are suitable as a second-year laboratory and are performed by students in two three-hour sessions. The experiments could be adapted to a three-hour laboratory by omitting either the sandwich, or the twist cell section, without compromising the learning objectives of the lab.

Keywords (Audience):

Second-Year Undergraduate

Keywords (Domain):

Analytical Chemistry

Keywords (Pedagogy):

Hands-On Learning / Manipulatives

Keywords (Subject):

Liquid Crystals
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  • Received: August 03, 2009

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