Number 219 (Story #1), March 28, 1995 by Phillip F. Schewe and Ben Stein|
LIQUID CRYSTALS CAN EXHIBIT BOTH SPATIAL AND TEMPORAL PATTERNS. With some of the orderliness of crystalline solids and some of the freedom enjoyed by molecules in a liquid, liquid crystals are important for biology (they form the membranes around the cells in our bodies) and as the basis for the multi-billion-dollar flat-panel-display industry, which depends on a phenomenon in which the rod-like molecules composing liquid crystals can rotate the polarization of light to create an on-or-off shutterlike effect. Liquid crystals are also important for the study of pattern formation in nonequilibrium systems (systems to which energy is being added). Scientists hope thereby to gain a better understanding of turbulence and possibly of morphogenesis (e.g., the question of where tigers get their stripes). Patricia Cladis of AT&T Bell Labs uses liquid crystals as a miniature laboratory for studying phase transitions. Heating one end of a sample and cooling the other end, Cladis has found that the phase interface between a pure liquid state and a liquid crystal state features spatial patterns (stripes with a characteristic "wavelength"); when, furthermore, the liquid crystal is "chiral" (i.e., when it has a handedness or helicity), the interface also oscillates with a characteristic frequency. Speaking at last week's meeting of the American Physical Society in San Jose, Cladis said she wanted to explore the connection between biological systems and the spatial and temporal order of liquid crystal patterns, a connection she calls "the dance of life."