The concept is simple: Boot up your computer and design whatever object you can imagine, press a button to send the CAD file to Lewis' headquarters in New Jersey, and two or three weeks later he'll FedEx you the physical object.
Lewis launched eMachineShop a year and a half ago, and customers are using his service to create engine-block parts for hot rods, gears for home-brew robots, telescope mounts - even special soles for tap dance shoes.
A futuristic MP3 player would be easier - but too obvious.
Then it hits me: Ever since I began playing electric guitar as a teen, I've wondered what it would be like to make my own instrument.
I remix various classic guitar designs by drawing the outlines of famous models, like the Fender Stratocaster and the Gibson Les Paul, then stretching and skewing their outlines to make my own mutations.
I had originally hoped to have it cut out of pine, like a normal guitar body, but when I explore the options for materials, I find that eMachineShop doesn't stock wood thick enough.
Eventually, he claims, you won't even need a middleman like eMachineShop, because every house will have its own personal fabricator.
But Gershenfeld, director of MIT's Center for Bits and Atoms, makes a reasonably good case and has already taken an important step: He has shrunk the personal fabricator down to a single room's worth of off-the-shelf tools, all of which are available right now.
For thicker materials, he suggests the $15,000 Epilog Legend 24TT laser cutter.
Anything you can sketch onscreen, the cutters can create, with tolerances as fine as one-thousandth of an inch.
That's so exacting you can punch out 2-D shapes that simply press-fit together, like six panels to form a box.