The shiny silver wafer is the size of a flea and thinner than a strand of hair. Like a fleck of iridescent paint or a tiny chip of plastic, it looks unexceptional at first. But through the microscope, a perfectly orchestrated world jumps out of the silicon. The patterns of black and white look like an elaborate M.C. Escher sketch. Then, it moves. Sluggishly but purposefully, a minuscule horizontal ladder rolls upwards, then down again, pushing against the surface below it. This passes for calisthenics in the intriguing new realm of micro-robotics.
Engineers at the University of California, Berkeley, are building mechanical fleas—mere millimeters wide—that not only do simple aerobics but promise to jump as energetically as the real insects. Team leader Kris Pister has dreamed of building robots this tiny for almost two decades, but only now has technology enabled his lofty goals. These bots will require sensors the size of sand grains—a technology Pister already is close to perfecting. Half a dozen of his spin-off ideas have spawned start-up companies, and his team is well on its way to putting these ingredients together into a functional micro-robot.
Pister imagines his bots exploring remote or dangerous nooks and crannies, such as caves or collapsed buildings. It's the kind of search-and-rescue that can raise privacy concerns for citizens who don't wish to be monitored. He acknowledges, however, that these uses are far in the future. "It's not clear whether they're going to be good for a whole lot of anything," he admits. "But it is still an incredibly fun project to work on."
The boy who loved Legos
A fortune-cookie motto adorns Pister's office door: "The great pleasure in life is doing what people say you cannot do."
For nearly 20 years, Pister has lived by this maxim. When he was a graduate student in robotics at Berkeley, engineers were only barely exploring how to create microscopic devices. But Pister realized that with newly shrinking technology, he could build miniature robots on tiny computer chips. "It occurred to me in a flash one day," he says.
In 1987, the Institute of Electrical and Electronics Engineers held the first Micro Robots and Teleoperators Workshop in Hyannis, Massachusetts, and a community began to form. When asked what most scientists thought of micro-robotics in that era, Pister laughs. "It was pretty far-fetched." He pauses for a moment then adds, "It's still pretty far-fetched."
Pister has never become discouraged, however. He got his Ph.D. from Berkeley studying processes used to make micro-robots. Since then, first as an assistant professor at UCLA and now back at Berkeley, he has continued toward his ultimate goal. Edward Lee, Berkeley's chair of Electrical Engineering and Computer Sciences, thinks Pister's work is paving the way for the future of micro-robotics. "He has really been one of the key pioneers of this area," says Lee.
Because Pister has developed tiny parts and micro-techniques with broad applications, some have become separate ventures. He coined the term "Smart Dust," for example, to refer to miniature sensing and communication devices. In essence, they are immobile micro-robots, stuck wherever dropped. Funded by the Department of Defense, Pister's Smart Dust research in the late 1990s led to devices the size of rice grains that sense, think, talk, and listen. He commercialized the work, founding a company called Dust Networks to sell his product.
Scatter this dust in the wind and it creates an invisible communication network. The network can sense whatever its designers choose: movement, heat, humidity, or sound, to name a few. The military imagines dispersing Smart Dust across enemy lines to track troop movements. Engineers could use the sensors to detect subtle vibrations in a bridge. Meteorologists could track weather patterns and not worry about losing expensive equipment in hurricanes and tornadoes.
One such vision has come true not far from Berkeley, in Northern California's redwood forests, where some of Pister's micro-sensors form networks across vast tree canopies. Hundreds of feet above the ground, the tiny wireless nodes collect data on humidity, temperature, light, and pressure. This lets Berkeley plant biologist Todd Dawson study microclimates in the lofty treetops.
"These forests are so massive that it's really challenging to obtain good climate information," says Dawson. "You would have to deploy too many weather stations to get a full picture."
Before Dawson started using Pister's wireless sensors, he says he would place two or three weather stations in each forest he monitored. To collect information, he had to climb the trees, sometimes 90 meters high, and lug down heavy equipment. Now, Dawson has many more sensors—180 in one redwood forest he studies. The nodes send information wirelessly to stations on the ground. "It's really allowing our research to move in new directions," he says of the technology.
The sensors are not yet perfect, Dawson warns. The system does not always collect data properly, he explains, and the sensors cannot be left unattended for more than a few days. But Dawson is confident that over time, the technology will improve and help him gather data in ways he has not yet imagined.
For researchers like Dawson, wireless micro-sensors stuck onto a tree seem sufficient, once perfected. But Pister is not satisfied with immobility. He wants Smart Dust to grow legs.
A bug's-eye view
Sarah Bergbreiter, one of Pister's veteran graduate students, runs her hand over a wooden tabletop. It looks and feels flat. But for a robot with legs as long as a strand of hair is wide, everything changes. "At that size," she says, "everything becomes an obstacle, even the roughness of the tabletop that looks smooth."
This is why walking micro-robots are so challenging to build: They trip and fall too often. But Bergbreiter came up with a solution after flipping through an issue of Nature in 2003. A researcher declared the froghopper, or spittle bug, as the jumping champion of insects, surpassing the flea. The spittle bug can leap two feet into the air, the equivalent of a human hurdling the world's tallest tree. Bergbreiter realized that when bugs want to get across rough natural terrain, they don't meander around every blade of grass if they can help it—they jump.
She quickly switched her research focus from building small wheeled robots to jumping micro-robots, and she became as driven toward the goal as Pister.
Though jumping makes movement more feasible for tiny bots, it also requires more force than walking. A former graduate student of Pister's had developed a semi-functional walking automaton, but Bergbreiter says most of his work didn't apply to her jumping flea. Jumping takes ten times more force than walking. "And that," she says, "is a pretty big leap in the world of engineering."
Since the spittle bug acted as Bergbreiter's muse, she looked toward the insect world for inspiration to design a jumping method. She started reading biology papers on fleas, becoming fascinated by their biomechanics.
Bergbreiter found that fleas jump not by flexing muscles but by storing energy in an elastic substance in their legs. The insects pull this stretchable band back until they are ready to take off. Then, they release it from hooks in their exoskeleton and soar skyward. Anyone who has snapped rubber bands across a room knows how this works.
Her forehead pressed against a microscope on a low lab bench, Bergbreiter shows how she mimics this efficient mechanism on a tiny scale. Under the lenses, a jagged yellowish ring sits in a black tray. Its edges are almost scalloped; it looks more like a bicycle chain than a rubber band. But this is, in fact, the way Bergbreiter's bots will get some height.
To make these, Bergbreiter starts with a thin sheet of silicone. She guides a high-powered laser slowly around the sheet, making two concentric circles. The path burned by the laser is thicker than the actual ring Bergbreiter wants; it's like cutting a shape out of construction paper using a chainsaw. This discrepancy makes the circle rough, but the ring that falls out is still usable.
A game of Operation
Although it makes the micro-robot jump, the tiny elastic band is only one piece. The real challenge is putting everything together. There are no tricks, only hours of squinting through a microscope, equipped with tiny needles to poke around the minuscule parts. Bergreiter has turned this process of micro-assembly into an art form.
"I just use some fine-point tweezers and don't have a diet Coke beforehand and I'm fine," she says. "It's a lot like playing the game Operation."
The most tedious part of her job is not peering into a microscope, however, but spending long days in the micro-fabrication lab transforming sheets of silicon into semiconductor parts. "The microlab is not the most pleasant place to work. It's like being in an airplane all day," says Bergbreiter.
The lab shines eerily yellow from filters on the lights and windows. The filters block ultraviolet light, which would ruin delicate materials. On the walls and ceilings, fans whir monotonously to suck the bad kind of dust out through huge metal ducts. Scientists wandering through the lab wear papery white from head to toe; only their eyes peek out. It looks like the inside of a spaceship.
Bergbreiter makes micro-robot appendages the same way computer companies manufacture chips. During her long days in the maze of ghostly rooms, she slides flat plates of shiny silicon into a furnace almost hot enough to melt glass. Inside the furnace, the silicon absorbs layers of vaporized chemicals. The last layer coated onto the silicon wafer, after it's pulled out of the furnace, is called photoresist: a light-sensitive substance that explains the lab's yellow tint.
Then, like playing with shadow puppets, Bergbreiter shines light onto the silicon through templates of the shapes she needs. Shadowed areas are protected, but where light hits, it develops away the photoresist in the same way photographic film is developed. This lets Bergbreiter chemically etch away the underlying layers.
When she repeats this many times with overlapping templates, a three-dimensional form emerges. Tiny hooks to pull the micro-rubber band and inchworm motors that look like piano strings appear in the silicon. Some geometric shapes inside the bot do not serve any designated purpose; they are just delicate place-holders. Empty space is dangerous in micro-assembly, Bergbreiter explains, since it leaves room for parts to bend the wrong way or fall out of place.
Her mechanical flea is not yet stable enough to fling itself into the air. So, Bergreiter conducted a test by laying the millimeter-wide hopper on its back and manually cranking its pogo-stick-like leg in the air. The leg kicked an energy-measuring device along a glass surface. The force her bug exerted, says Bergreiter, was enough to propel it 20 centimeters upward—more than 200 times its body length. She must finish connecting all the bot's parts, however, before she can test that estimate.
The end of privacy?
A troop of bots that descends on a collapsed building to find survivors in the rubble can just as easily find humans for an insidious purpose. Mechanical fleas that record sound can be strewn through a building to obliterate privacy. Flying micro-bots could follow us anywhere. Are these real concerns?
Pister jokes that when his students come up with a tiny privacy-invading bot, they'll bug his office first. But when asked whether he talks to his students about the ethical issues of creating such a privacy-threatening technology, Pister gets serious.
"Absolutely," he says. "I think any new technology presents both benefits and risks. And it's important to acknowledge the risks." Invasion of privacy, says Pister, is the biggest concern he foresees anyone having.
There are more concerns than just privacy, says Patrick Lin cofounder and research director of the Nanoethics Group, an independent organization based in Santa Barbara, California, that studies the societal implications of nanotechnology. "History shows that technology is virtually always misused for unintended purposes," he says. "One might reasonably foresee that disgruntled teens in the future, once micro-bots are widely accessible and come down in cost to build and program, will unleash rogue micro-bots just as they do with Internet viruses today."
Beyond these misuses, Lin predicts environmental concerns surrounding such small technologies. "If micro-bots are so small, and look as well as behave like insects, will some animals mistake them for food, and how does that affect the ecosystem?"
However, Lin does not think scientists should stop all micro-robot research. "Any call to halt development of such devices seems to throw the baby out with the bathwater," he says. Instead, he asks researchers to foresee the risks of their new technologies and brainstorm how they can prevent them.
Most ethicists agree there is a middle ground between calling off potentially harmful research and moving ahead at full speed. Mainly, scientists don't consider the risks often enough, says Rosalyn Berne, a University of Virginia ethicist who specializes in nanotechnology. There is not enough time in scientists' days for them to ponder the societal effects of their work, she says, blaming the high-paced, competitive nature of science research.
"Nobody wants to slow down," Berne says. "If you really want to take a step back and look at the ethical questions, you have to slow down." (For his part, Pister chuckles at the notion of slowing down, since it's taken him so long to get where he is today.)
Berne also proposes engineering ethics courses for undergraduates and graduate students to teach future scientists how to consider the implications of their work. Understanding these, she says, could affect the way engineers design and build things. If a researcher takes extra time to add one more layer of security to an electronic device rather than rushing to market, it could prevent future misuse.
If this deceleration of engineering does not happen, Berne says, privacy will be extinct within 50 years. "A lot of things are going to be completely new in terms of our value system," she says. "We'll get used to being watched."
Lin thinks that our standards will evolve along with the technology. "Even if micro-bots are capable of infringing on our current privacy expectations, it's not clear this is a bad thing," he says. "It could just be that we need to evolve our notion of privacy—yet again."
The coolness factor
Micro-robots are far from creeping off store shelves into our homes. But since Pister's flash of an idea 20 years ago, they have moved closer to reality. He envisions a day when personalized micro-bots can monitor your house for everything from humidity to dust.
"Is it possible we get to the point where robots are under a dollar each?" Pister asks. "Yes, it's certainly possible. When might that be, in 10 years or 50? I have no idea." He pauses for a moment. "I've been working on this for more than 15 years, and it's always felt like it's just a couple of years away."
The thrill of gazing through a microscope at the tiny moving world he has created is enough to keep Pister going. "I think the excitement and the rewards I can get from this are not very different from the excitement that my children feel when they build a nice tower out of blocks," he says.
In the lab, Bergbreiter is peering through a microscope. She shines a thin ray of light onto a bot that is clamped, upside-down, under her scope. "Come on," she urges it. "I know these legs move."
She glances up at a computer monitor that displays a gargantuan image of the tiny bot. Suddenly, a leg starts to roll upwards.
"There it goes!" she cries. "It's just so cool!"
ABOUT THE WRITER
Sarah C.P. Williams
B.A., biology, The Johns Hopkins University
Internship: Yale School of Medicine news office
I spent the summer writing for the Yale School of Medicine and have now relocated once more, to Washington D.C., to intern for Science News magazine. I grew up on an apple orchard in Vermont and love cookies, biking, and my Great Dane puppy Zetta (whose name means 1021 because she's so big). More of my writing can be found at www.sarahcpwilliams.com.
ABOUT THE ILLUSTRATORS
Juan Cristobal Calle
B.S., biology, University of Los Andes, Bogotá, Colombia
Long before I enrolled in scientific studies, my passion was reading and illustrating comic books, and of course, every book with animal and plant illustrations on it, as they showed me the hidden world beyond. By the time I was finishing my career, I was illustrating the thesis works of some of my friends, and then I realized that was the path I should follow. Since then I have been involved with several publications concerning flora and fauna of my country, sponsored by institutions concerned by the situation of our natural resources. I have also been working on editorial illustration, character design and animation for the last year and a half, getting more acquainted with the digital world of illustration and video. My goals are to teach all the knowledge to the people in my country, continue if possible producing illustrated field guides, and move deeper on the terrain of character design for animation, movies and video games. Just for reference, I am a Star Wars fan.
Suzannah L. Alexander
B.S., biology, Oklahoma Christian University
Graduate certificate, editing, University of California, Berkeley
When I was little, I dreamt of being an illustrator, but when it came time to go to college, I chose to study a more practical subject—biology. All of the documentaries on PBS first piqued my interest. I find science to be both challenging and fascinating, and I love how everything in science and life is pieced together like a giant puzzle. On a roundabout path, I found my way into a career as an editor for science textbooks, and this work has taught me how important art is in education. It has also rekindled my first love of drawing. I am excited to build upon all of my experiences in art, science, and publishing in order to create and teach through illustration.