School Notes: School of Engineering & Applied Science
March/April 2015

Engineering the right notes

In the newest design course at the Center for Engineering Innovation & Design (CEID), students created their final projects using cutting-edge computer software, 3D printers, and laser cutters. But they also used a simpler tool: a tuning fork. Cotaught by School of Engineering & Applied Science senior research scientist Larry Wilen and Department of Music lecturer Konrad Kaczmarek ’02, Musical Acoustics & Instrument Design explored the intersection of engineering principles, musical theory, and the physics of sound production, culminating in the design and construction of one-of-a-kind instruments. For example, Yale College junior Catherine Jameson invented the “Lothlóritar,” a stringed instrument playable only by two people working together, while the “Clip-B-Audio” from Yale College senior Rachel Perfecto uses pencil graphite and the metal clip on a clipboard to literally draw music—lines drawn closer to a clip produce higher pitches than lines drawn farther away. Other novel instruments included an 11-string oud inspired by ancient Mediterranean instruments, an electric cello designed using the technology of the theremin, and a keyboard that blows air across glass bottles filled with “tuned” amounts of water. “By the end of the course,” Wilen said, “the musicians became incredibly skilled engineers, and the engineers were amazing musicians.”

Liquids that make solids stiffer

According to associate professor of mechanical engineering and materials science Eric Dufresne ’96, the stiffness of liquid drops embedded in solids has something in common with Goldilocks: while large liquid drops are softer than the solid that surrounds them, extremely tiny liquid drops can actually be stiffer than certain solids. And when “just right,” the liquid and the solid have the exact same stiffness. The key is surface tension—a contractile force that allows a cup of water to be filled slightly above the brim without spilling. That same force enables tiny liquid droplets to resist deformation so strongly that embedding many of them in silicone resulted in a 30 percent stiffer material. “We found that the importance of surface tension is inversely proportional to the size,” said Dufresne. “What’s a negligible force for big things becomes a strong enough force for very small things that it affects the whole material.”