(FORTUNE Magazine) – CAMBRIDGE, MA. Founded 1993 Revenues: $500,000 Employees: 12 Private

You can tell SensAble Technologies is cooking by the baby snoozing in its chairman's office. It has never advertised its one product, the Phantom, a $20,000 device that gives computer users the uncanny sensation of fingering objects that don't exist. Yet it has been swamped with orders since inventor Thomas Massie and his wife, Rhonda, formed the company while pursuing engineering degrees at MIT--Massie, 25, designed the device as a senior. SensAble's growing staff now shares the backlog burden, but the Massies' schedule is even more hectic--they often bring their infant daughter to work, and a crib sits next to Chairman Dad's desk. Says Mom, a mechanical engineer: "I can get a lot done during naps."

Such is life when you're stirring a revolution: SensAble's goal is to change radically the way we interact with computers, by adding the sense of touch. "If this takes off, it won't just be an incremental technology shift," says Douglas Kingsley, a venture capitalist at Advent International, which recently led SensAble's first round of financing.

At first glance, the Phantom seems an unlikely breakthrough: A thimble on the end of a small, jointed metal arm. But magic happens when you stick a finger in the thimble and move it around--you seem to be touching invisible objects, thanks to forces exerted against your finger by computer-controlled electric motors on the arm. With two Phantoms, for thumb and index finger, you can pick up things that exist only as computer bits.

The illusion can be magnified by 3-D graphics that let you see the virtual objects. Body parts are especially riveting. One customer sent SensAble a living wrist--a Phantom-controlling program that conjures the pliant feel of a human wrist, replete with skin, tendons, and a beating pulse. "The heart rate seemed dangerously fast when it was run on our faster processor," says MIT researcher Kenneth Salisbury, who co-developed the Phantom.

Customers include General Electric, Mitsubishi, Sandia National Laboratories, and the U.S. Navy. The devices sold so far are for tactile studies on things like simulated fighter-plane controls, drug molecules, mineral deposits, and human spines. Before long, aspiring surgeons are likely to hone their skills by cutting into virtual patients instead of us, and auto designers will sculpt new models from virtual metal. The Phantom's 458,000 steamy possibilities are left as an exercise for the reader.

SensAble plans eventually to introduce cheaper models--competitors already have unveiled prototypes of low-end "force-reflecting interfaces," such as videogame joysticks. But it's in no rush to enter the tricky consumer market. Says President Bill Aulet: "People come to us not because we have the lowest cost, but because the Phantom is wicked cool and they just gotta have it."

--David Stipp