Ron Fearing’s lab is a mess. Scraps of stainless steel and strips of flexible ceramic lie scattered near glass slides stained with a rusty liquid. The result is flies. Tiny, micro-machined, robotic flies.
You wouldn’t mistake the U.C. Berkeley professor’s creations for actual flies – not yet. The robotic insects are a bit larger than a plump housefly. Their translucent orange composite wings and shiny steel and ceramic thoraxes are quite clearly mechanical. But a machine is emerging in the shape of a fly – the “Microfly” – and so is the pest’s gift for pulling 2G turns with bursts of speed up to 30 mph.
We’ve all swatted futilely at the living version of the unwelcome bugs. They have an annoying talent for evading destruction and an irritating habit of hovering nearby during private moments. These are great skills if you are a fly, but as it happens, they also come in handy if you are a spy.
Imagine sending 1,000 Microflies into a hostile building. Like the insects they are designed to mimic, they aren’t the smartest creatures in the world. Some are bound to get squashed, but some are bound to survive and make it to where you want them to go-or, in this case, where others don’t want them to go.
That is what the U.S. Defense Department and the Office of Naval Research have in mind, and why they are paying Fearing’s team $2.5 million to get the job done. It’s just one of several “biomimetics” projects the government has been funding since 1998 that look to nature for engineering inspiration when developing the latest robots for warfare and espionage.
There is a mechanical pike at M.I.T, and a robotic lobster at Northeastern University in Boston. It’s not that robotic fish and crustaceans are going to march into battle, but by studying and mimicking their highly efficient systems, scientists hope to build better boats, submarines and underwater mine-clearing equipment.
That may be fine for the fish, but the Microfly is a little different. The government backers of Fearing’s project hope the little mechanical buggers will someday be the smallest spies in the field: Cruising at 10 feet per second with a range of almost 1.5 miles, they will patrol buildings and bunkers, hunker down in shadowy caves and, with miniature onboard sensors run by a minuscule operating system, send back images and sounds to their covert masters. And, they’d cost just $10 a pop.
That’s the plan, but right now Fearing is focused on getting his Microflies off the ground. “Flies can put a fighter pilot to shame,” says Fearing, who has a doctorate in electrical engineering. “But there is quite a gap between what nature is capable of and what our machines are capable of.”
Fearing says this as he tries to fire up the PC in his office. The room is a slightly tidier version of his lab. Jumbles of books with titles like “Applied Robotics Analysis” share space with piles of paper. On one wall a white board is scribbled with diagrams and equations showing how to run a robot without burning up a battery and how to program a simple control system. Another wall is adorned with a poster of what looks like a Japanese doll. It is a photograph of one of the first robots made, an 18th century wind-up machine that served tea. Fearing, 41, has been fascinated by robots since reading science fiction as a child.
Out of respect, he has sworn off crushing live flies, at least for the time being, he says. As he tries to get the sound working on his computer he further extols the virtues of the common housefly, praising its power and hardiness. “Flies are the most sophisticated of the insect flyers, with high lift-to-weight ratio, great acceleration and visual sensing, and great maneuverability,” he says.
Humble Beginnings
Like most scientists, Fearing is barely able to use a PC. He could probably take it apart and put it back together so that it walks, but he can’t make sound come out. Finally he gets it working, and sound now accompanies a video of a fly hovering in slow motion.
When he and his team started the project in 1998 the first hurdle was building a wing assembly that worked like a real fly’s, mostly because no one at the time knew how insects fly. The concept of lift and thrust is well understood in birds with their large wings, but scientists couldn’t explain how something as large as a fly could get its body off the ground with those tiny transparent wings.
It took research by another Berkeley professor, biologist Michael Dickinson, using an oversized pair of insect wings beating through the heavy atmosphere of high viscosity mineral oil, to figure it out. It turns out that flying insects use three different motions to gain lift and thrust.
First, the high angle of their wings as they flap generates a large swirling vortex on the top surface of the wing that pulls it upward. This is called “delayed stall,” and it was explained by researchers before Dickinson applied his MacArthur Foundation-genius-award brain to the problem. But delayed stall couldn’t provide enough lift on its own to permit a fly to pull off the acrobatic stunts we so often witness.
Dickinson found two other forces at play. At the end of each stroke the insect’s wing rotates and creates another lifting force in much the same way a baseball pitcher creates lift in a ball by putting spin on it. Dickinson also found that because the insect wing is always passing through the wake of the previous stroke, it is able to capture energy from the wake to force the wing forward. This final force was dubbed “wake capture.”
With Dickinson’s research, Fearing had the motion he needed to replicate in his mechanical wings for flight and set out with a 20-person team to build them. The resulting wings are thinner than a sheet of paper, 10 millimeters long and three millimeters wide – the dimension of a real fly’s wing. The flapping and rotation is accomplished by attaching the wings to a complicated joint, which in turn is attached to an equally complicated differential.
Passing current through two strips of ceramic material attached to the differential activates the wing. By flexing the ceramic material in different phases Fearing is able to make the wings flap and rotate. The latest version of the Microfly is powered by 150 volts and a rack of equipment. Eventually it will run on just 20 milliwatts, about 1/50th the power of a D battery. Three solar panels that double as landing gear will provide the juice.
Because the entire assembly must be lighter than a paper clip, it is actually folded together like origami. Lasers first score and cut thin stainless steel strips. Other materials are bonded onto the strips, and then patient post-docs fold the pieces together. Even with the laborious folding, Fearing can go from a design to a working prototype fly in less than a week. The rapid prototyping process will soon be automated.
“The folding technique is perfect for building any high-precision mechanism between one and 10 millimeters long,” Fearing says. So perfect, he has filed a disclosure with the U.C. Berkeley Office of Technology Licensing on the fabrication technology for the Microfly skeleton.
He’s now able to get the fly wings to move at the required 150 beats per second, but that doesn’t mean his robotic insects can fly on their own. Back in the lab, 02Iota, the official name of the Microfly, sits in an airtight plastic box attached to a rigid tether. “It’s like a fly on training wheels,” Fearing says. “He doesn’t have enough force to lift himself up yet, but we are close.”
Long-Range Flight
Fearing plans to get the fly hovering on its own by the time his government funding ends in the middle of next year. Free flight is another five years out and full spy missions another decade, he says.
Hovering will cost another $1 million, Fearing says. As to the price of more complex mission, it’s hard to gauge. Sensor development would be extra, but it could leverage research already underway at Cal and other places. “It could be $10 million or $100 million to do the complete development,” he says.
“This would be a better task for a company than a university,” he says, suddenly sounding more like an entrepreneur than a professor. He plans to look for more funding before his government grant runs out, although he has yet to approach any venture backers.
While his current sponsors have espionage on their minds, Fearing sees other uses for the flies as little agents in homes monitoring security, fire, and water taps mistakenly left running.
“The home environment is pretty complicated, so it makes more sense to fly over things,” he says, “Besides, these things are intrinsically safe. If a fly bumps into your kids they are not going to get hurt.”
And then there is the fly-as-fun market. “I see entertainment as an early application. They could be radio controlled, so you could do aerial choreography.” It may not seem like fun to everyone, but Fearing also imagines the thrill of sending out a legion of robotic insects to battle the real thing a sort-of combination Stratego/bug zapper.
“With home-based micro-manufacturing capability, perhaps an ambitious teenager could do this on their own in five to 10 years,” he says. “It’s all possible, it’s just a matter of money and interest.”
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