Honey, I shrank the motor

In an obscure corner of Caltech, Philip Ball meets the engineer who rose to Feynman's nano-challenge

You are in the Tate admiring the multiple frames of Marilyn Monroe, when up sidles an old man with tousled, silvery hair. "Like it?" he asks. "Well, I painted it." I felt I'd had a similar experience at the California Institute of Technology in Pasadena, visiting a shrine to human ingenuity.

It stands behind glass in the gloomy hall of the physics department and is clearly from another era. There are yellowed, typed captions on curling cards, some with hand-drawn diagrams. A bakelite push-button illuminates an assembly of mirrors and lenses in black-enamelled metal mountings. But the star attraction is an icon from the prehistory of the hottest science in town: nanotechnology. The lenses are there so that you can just see it. It looks like a grain of black grit, but when you squint down the microscope you can make out a tiny, exquisite assembly of posts, plates and wires. It is an electromagnetic motor, made from magnets and coils of wire, and it's less than half a millimetre across.

A button once switched the motor on so you could see it whirring under the microscope. But no more - the feckless Caltech students burnt the coils out years ago. The wires are, after all, just 1/80th of a millimetre wide, which is thinner than a human hair.

The motor was assembled in 1960 in response to a challenge from the famous Caltech physicist Richard Feynman in a manifesto now seen as the founding text of nanotechnology. All this seemed like ancient history, until a man with a white crew-cut wandered by. "You look mighty interested in that little motor," he said. "Well, I'm the man who made it."

Bill McLellan graduated from Caltech in 1950 with a major in mechanical engineering. He worked in industry for the next 20 years, mostly building electric-current meters called galvanometers. In the 70s he returned to Caltech as an engineer for astronomical telescopes. Now he has an honorary position on the campus. Although electronics wasn't his speciality, as a former radio ham, McLellan knew a thing or two. "I'd never designed a motor," he said, "but I knew how they worked." So when he read about the challenge, "I knew how to make it and I wondered why nobody did."

In December 1959, Feynman gave an after-dinner talk to the west coast section of the American Physical Society. It was titled There's Plenty of Room at the Bottom. "Why cannot we write the entire 24 volumes of the Encyclopaedia Britannica on the head of a pin?" he began by asking. If information was encoded in binary form - as strings of noughts and ones, just as it is in computers - and if each 'bit' of information was composed of a heap of 100 atoms, then he calculated that all the books in the world could be written inside a cube 1/200th of an inch wide.

"Computing machines are very large," said Feynman, "they fill rooms. Why can't we make them very small, make them of little wires, little elements - and by little, I mean little." This is precisely the dream that many nanotechnologists are now pursuing - trying to figure out how to make computers, memories and machines using individual atoms or molecules as building blocks. In today's silicon chips, the wiring can be as little as 80 nanometres - 80 millionths of a millimetre - thick. A Pentium 4 microprocessor chip, the size of your little fingernail, holds 42m transistors. But if nanotechnology fulfils its promise, circuits are going to get a lot smaller.

"It is my intention," Feynman concluded, "to offer a prize of $1,000 to the first guy who makes an operating electric motor which is only 1/64th inch cubed." After the talk, Don Glaser, a physicist who won a Nobel prize in 1960 for inventing the bubble chamber, told Feynman: "You should have made it smaller." But Feynman was confident.

"He really didn't believe it could be done," McLellan said. "But he found out." In June 1960, he reread Feynman's speech, "I thought, my gosh, nobody's done it. Of course, when I got into it I realised why: they were smart, it was too much work. But in general they didn't have a clue how to proceed." So he got down to business.

"Most of the galvo technicians had been watchmakers, so I learnt from them," McLellan explains. For example, they taught him the trick of making iron wire thinner than the narrowest gauge commercially available by rolling it between two microscope slides, as if rolling out a line of pastry.

After five months of labouring with the almost laughably crude tools now in the display at Caltech, including a toothpick and a fine-gauge paintbrush, McLellan had assembled 13 separate components into a working motor. He took it to show Feynman.

"He'd seen a lot of cranks come in with motors, who didn't understand the challenge," says McLellan, "and I brought in a big box, and he said 'Oh, here's another one of them'. And I opened my wooden box up and there was my microscope. He said, 'Uh-oh, nobody else brought a microscope.'"

"So I set it up," McLellan recalls, "and he played with it for a while." Finally he admitted McLellan had done it. "He wrote me a cheque, and in the letter he said it met the specifications." Feynman was a little chagrined - but not because he'd lost $1,000. "Feynman's disappointment was that it didn't get the new method," said McLellan. But there was some consolation when McLellan gave him one of the 10 little motors. "He loved it."


McLellan's motor is gargantuan compared with the natural devices that operate inside living cells. Motors made from single protein molecules carry tiny molecular packages around the cell, and these "motor proteins" also control the contraction of muscle fibres. Four years ago, a team of researchers at Cornell University hooked up a nanoscale metal blade to an enzyme called ATP synthase, which spins round on a spindle anchored in the walls of cells when fed with a chemical fuel. They watched the blade as it whirled like a little propeller, powered by this molecular motor. ATP synthase is just 10 nanometres across: about 50,000 times smaller than McLellan's device. But no one has yet figured out how to make such a molecular-scale device from scratch, rather than adapting one from nature.

McLellan is convinced that his miraculous little motor was worth the effort. "Kids would write in saying, 'I'm going into that miniaturisation'. So it inspired people in a good way. Even though it didn't produce what Feynman wanted, the results got everybody interested. It sure stirred up interest."

· Small Worlds, a three-part survey of nanotechnology, continues on Radio 4 on Wednesday at 9pm