A THREE-SIDED SOLUTION

WHO KNEW? Harvard researchers using an algorithm they developed to design mechanical devices that perform at an optimum level, have discovered that a triangular tap produces smaller droplets than a circular one. A slightly concave, threesided nozzle will produce droplets 21 percent smaller than those emitted by a round tap. In theory, a triangular tap could produce drops a mere 8 billionths of a millimeter. That's a fairly significant gain if the cost of the material being sprayed is a consideration, says Michael P. Brenner, a professor of applied mathematics and applied physics in Harvard's division of engineering and applied sciences. he and graduate student Henry Chen devised the algorithm.

One possible use is the manufacture of silicon chips and bio-chips that are sometimes patterned by fine sprays. It could also result in extremely high-resolution ink-jet printers. A few companies have called to ask about the finding, Brennan says, but it's too soon to say if triangular taps have great commercial appeal. More important, he says, the finding shows that the algorithm can be used to help solve problems in the design of engineering mechanisms that were beyond the ken of previous predictive formulas. In that sense, he says, the nozzle demonstration is good because, although it's a complex problem, the result "is one you can visualize. It's easy to explain to a person on the street." Certainly easier to explain than the optimum shape for a microelectromechanical system device.