Renate Ondris-Crawford

Characterization of the cylindrical cavities of anopore and nuclepore membranes

The microscopic properties of the inner surface of the cavities of Anopore and Nuclepore membranes are investigated with scanning electron microscopy (SEM), nitrogen adsorption isotherms, and deuterium nuclear magnetic resonance (2H‐NMR). Useful information about the cavity orientation and morphology, and internal surface area is obtained. Analysis of SEM photographs yields estimates of the surface area and the porosity of these membranes which complements the adsorption results. The orientation of liquid crystals permeated in the cavities of Anopore and Nuclepore membranes is probed with the 2H‐NMR technique. It is found that the orientation of the liquid crystal molecules is governed by the confining volume and surface conditions. The 2H‐NMR spectral line shape of the confined liquid crystal also provides information on the substrate morphology and roughness that is consistent with SEM and adsorption experiments.

Polymer dispersed liquid crystal infrared light shutter

We have developed a polymer dispersed liquid crystal (PDLC) device for operation in the midinfrared region of the electromagnetic spectrum. This device can be incorporated in thermal imaging systems that utilize pyroelectric vidicons for night vision applications. The infrared electro-optic properties of several PDLCs as a function of substrate, droplet size, film thickness, and applied ac voltage are examined using infrared spectroscopy, electro-optic and differential scattering measurements, and static video analysis.

Liquid crystal displays: molecules at work

Liquid crystal displays have become an indispensable means to deliver information. Their fascinating optical properties are described along with simple experiments that can be performed in the classroom to complement discussions on the structure of matter, phase transitions, polarization, dielectric constants, refractive indices and light scattering. Liquid crystals also serve as a medium to link basic physics to technology and other scientific disciplines.

Resource letter: LC‐1: Liquid crystals: Physics and applications

This Resource Letter provides a list of references on liquid crystalline materials emphasizing both their fundamental properties and their practical uses in flat‐panel displays and electro‐optic applications. We have labeled those articles that can be used by students with little or no physics background and no prior knowledge of liquid crystals with an E (elementary), those that require a physics background but can be read by undergraduates with an I (intermediate), and the articles geared towards graduate students and researchers in the field with an A (advanced).

Liquid Crystals: A Bridge Between Science and Technology

As volunteers for ALCOM Education Outreach, the education program of the National Science Foundations Science and Technology Center for Advanced Liquid Crystalline Optical Materials (ALCOM), we take advantage of the spectacular optical and electrooptical properties of liquid crystals to teach basic principles of optics to students from kindergarten to beginning college. Normally, students are taught predominantly about the three phases of matter—solid, liquid, and gas—but plasma and liquid crystals are often overlooked or omitted entirely. Some students are already aware of the existence of liquid crystals because they are familiar with the acronym LCD (liquid crystal display) which they associate with computer games, laptop computers, small televisions, and appliances that use LCDs to display information. Our science education program uses LCDs to teach basic scientific principles and to demonstrate the bond between science and technology. Understanding the underlying physical principles of the LCD requires basic concepts from physics, chemistry, and engineering, so liquid crystals are ideal materials to show the link between the various scientific disciplines.