It arrives in a glossy black box, its sensual shape traced in shadow. My fingers grasp at the perfectly positioned pull-tab and slide the box open. There it sits, the product of the creative minds that helped birth Google’s Project Ara modular smartphone and projects for NASA and DARPA.

It is a straw. Apologies–it is the STRAW, or Suction Tube for Reverse Axial Withdrawal, designed to mix the black-and-tan-esque strata of McDonald’s new dual-layer Chocolate Shamrock Shake in perfect proportion.

[Photo: courtesy the author]

“My first reaction was, that doesn’t seem too hard. We could have a double straw–one longer, one shorter. No problem,” says Seth Newburg, principal engineer and managing partner at NK Labs, which teamed up with JACE Design on the STRAW (the two companies also worked on Project Ara together). “Then we immediately thought, once you get halfway down, one straw is going to start sucking air . . . It’s one of those things that seems so simple, but as we got into it there were a lot more issues exposed. It turned out to present quite a few engineering and scientific challenges.”

The STRAW looks something like a saxophone, or a fish hook, with fluted holes. It’s the product of comedic over-engineering, involving white boards, physical prototypes, CAD models, and even fluid dynamics simulations.

“A lot of designs we came up with would work well when the shake was full, or might work when the shake was empty, but in a lot of situations, we found if we didn’t get the diameters just right, we’d end up drawing in air, or the first few sips would be good, but you had to wait a minute for the straw to be recharged,” Newburg says.

Video: 74 Years Of McDonald’s Marketing In Two Minutes

The breakthrough happened in a white boarding session. “One of our team members said, ‘How about we change this? Instead of drinking the bottom up, we drink from the top down.’ They drew a J-shaped straw.”

The end of the J would suck in shake, as would two large holes on its tip, allowing you to get the mix you want. But as the shake dipped below the J holes, those openings wouldn’t start sucking in air as a straight straw with holes would. Instead, you could continue sucking because of a vital third hole, on the bottom of the straw. As long as there’s shake coming through the bottom, you close off the pressure system to the tip of the J.