The whole thing started innocently enough. Vin Crespi, Penn State's Downsbrough professor of physics, attended a seminar on liquid crystals.
Crespi is a theoretician with a yen for experiment: His specialty is condensed matter. He recently figured out how to make a tube out of carbon molecules that measures only six atoms across, smaller and sturdier than anything yet attempted (see the January 2002 R/PS). Liquid crystals, however, fall somewhere outside his regular orbit.
They're halfway between a solid and a liquid, he says. They're crystals, so there's some order to them. He picks up a thick bundle of paper clips from his desk, a magnet apparently hidden in their midst. Kind of like this, he says. Rod-shaped. Free to wander a bit among each other. But always facing the same way.
Sometimes, he continues, these molecules are twisted into corkscrew spirals. These spirals are chiral: that is, some are right-handed, and some are left-handed. The two varieties are mirror images of one another.
Crespi pops up and walks quickly to the lab next door. Two research assistants glance up as he hunts down a couple of ordinary screws. Grasping a screw between thumb and finger in each hand, he places them side by side, touching, and rolls them against one another, trying unsuccessfully to match their spiral tracks. See, they don't mesh very well, he says. Normal screws are all right-handed. But a right-handed screw and a left-handed screw would mesh perfectly.
So it is with chiral liquid crystals, he heard at the seminar: When they're all left-handed or all right-handed, they don't mesh at all. Their uniformity creates some funny properties, as Crespi says. And I started thinking, These are not the only things that are chiral.'
Maybe it was residue from an Italian-American boyhood. Maybe it was close to lunchtime. But the things that danced into Crespi's head at that eureka moment were varieties of pasta; specifically the pale-blond, seemingly endless varieties of spiral pasta. Rotini. Fusilli. Radiatori. Tortiglione. Currently, he realized and later wrote, all spiral pasta are produced and packaged with a single chirality, since the machines used in their production are designed to produce identical pieces of identical handedness.
But what if they weren't? What if the pieces of pasta in a given box were evenly distributed, left- and right-handed, so that they might fit together snugly? The question gathered force in his mind. Pasta is not very dense, not very expensive to make. The packaging and shipping costs are comparatively high. . . . Mixed chirality, Crespi thought, might save considerable volume—and money.
I went out and bought boxes of every type of corkscrew pasta I could find, he remembers. He was looking for complementarity: a pair of spirals that would nicely marry. At last, on a trip home to Chicago to visit family, he stopped into an Italian grocery and found what he was looking for.
The experiment took place in Crespi's kitchen. I put equal amounts of all left-handed and all right-handed pasta into identical glass jars, he explains, turned them sideways, shook them ten times each, and marked out how high the pasta measured in each jar. Then he dumped the two containers into a bowl, mixed the corkscrews together thoroughly, placed even quantities of heterogenous pasta back into each container, and measured again.
He describes his findings in an invention disclosure he subsequently filed with the University's Intellectual Property Office. The pasta of mixed handedness occupies a volume which is 5-10% less than that occupied by the pasta of uniform handedness, reads the relevant paragraph in section III. The exact amount of the reduction in volume depends on the specific shape of the pasta chosen and the degree of mixing and settling. For deviations from a 50/50 ratio of the two handednesses, the packing density of the mixed chirality pasta is still increased, but typically by a smaller amount.
So, Crespi says. The experiment was a success, as far as that goes. He pauses, flashes a slightly pained smile. But then it turns out there's the marketing question to consider. Pasta producers, it gradually became clear, might not be terribly interested in increased packing density. My take on it was you could put on the box 10% more!,' Crespi says; but nobody seemed to agree with me. In the end the patent office decided to take a pass on the idea.
Crespi shrugs. He is not discouraged. He has other patents on the books and in the works, and plenty of other ideas. But this one, he admits, is probably dead. Unfortunately, I ate the experiment, he says. I mean, I kept that pasta around for a while. But eventually I ate it.