Material Witness

news & views MATERIAL WITNESS MATERIAL CROSS PURPOSES Some stories of serendipitous David Brewster, who hoped to use discovery have the non-sequitur Herapath’s material in the eyepiece character of myth. People routinely to make kaleidoscopic images from recount the tale of the optical interference colours. polarizer herapathite thus: a The problem with such applications student of the Bristol toxicologist was that it was tough to grow large William Herapath dropped iodine crystals. Land took a different into the urine of a dog fed on route, making a viscous colloidal quinine, and precipitated green dispersion of small needle crystals crystals that Herapath studied under that he aligned in plastic sheets by the microscope. Noticing that the squeezing the liquid through narrow PHILIP BALL translucent, needle-like crystals slits. Land’s initial motivation was were sometimes dark where they not photography but antiglare films with William von Eggers Doering overlapped, Herapath realized that for vehicle headlights. In the Second in 1944. this was a polarizing medium. Not World War, this application, which Although herapathite did not the first, for the silicate mineral was never adopted for cars, improved at once fall wholly out of use, its tourmaline was already used in that the visibility of enemy vessels at sea diminished importance perhaps respect. But tourmaline was rare and by cutting out polarized reflections of explains why its crystal structure has expensive, and that at a time when sunlight on water. never been deduced, which meant polarization effects had become All the same, it was a wartime that its polarizing properties have central to optics. shortage of quinine that put paid to not been fully understood. Bart Kahr But why was a dog being fed on herapathite filters. Supplies of quinine and colleagues at the University of quinine, and why collect its urine? extracted from Cinchona trees in the Washington in Seattle have now Even in the mid-nineteenth century Dutch East Indies were cut off, and solved this rather complex structure this seems an odd thing to do. Of the limited quinine available was (Science 324, 1407; 2009). It is course, quinine was then an important needed as an antimalarial drug for lamellar, with the quinine molecules antimalarial drug, but that hardly troops fighting in the tropics. This complexed to triiodine ions linked solves the mystery. In any event, forced Land to develop new filters into extended chains. Delocalized this story is usually drawn from the based on aligned polyvinyl alcohol excitons on these chains lie at the root account of Edwin Land, the pioneer dyed with iodine. It was also what of the light-absorbing properties. So of Polaroid photography, who made prompted his Polaroid Corporation herapathite now joins an illustrious herapathite famous in the polarizing in Cambridge, Massachusetts, to hire list of historically important materials, filters of his new technology. Land the dazzling young Harvard chemist including Prussian blue and Mayan came across herapathite in an account Robert Woodward as a consultant, blue, understood only by the grace of the kaleidoscope by its inventor stimulating him to synthesize quinine of modern crystallography. ❐ LIQUID CRYSTALS More than display fillings With liquid-crystal displays now ubiquitous in everyday life, liquid-crystal research is moving beyond these applications and evolving in entirely new and unexpected directions. Ralf Stannarius oday, liquid-crystal (LC) devices have in Bandol, France, organized by Jan and research areas that sometimes didn’t even practically conquered the electronic- Sven Lagerwall, and bringing together realise that LC research was relevant to Tdisplay market. With the advent of European scientists representing different their work. commercial 100 inch (2.54 m) displays, perspectives of LC soft-matter research, Scientists from Europe, starting one might wonder whether everything demonstrated impressively that the field has with Reinitzer and Lehmann in the desirable has been achieved in LC research. broadened enormously in recent years. It is late nineteenth century, pioneered the Time to move on to another research being stimulated by contemporary trends discovery and investigation of LCs. field? Not at all. The European Science in soft-matter science, and is fruitfully Understanding of the field grew in 1 Foundation (ESF) Exploratory Workshop influencing scientists from neighbouring particular during the last decades of NATURE MATERIALS | VOL 8 | AUGUST 2009 | www.nature.com/naturematerials 617 © 2009 Macmillan Publishers Limited. All rights reserved.

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