Conventional wisdom has it that electronics and water don’t mix: You know this even if your cellphone has never slipped from your hand into, say, the bathtub. So it was with some alarm this past summer that I watched John A. Rogers cheerfully shoot water at an integrated circuit.
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We were in a lab at the University of Illinois at Urbana-Champaign, and Rogers—a materials scientist there, and the picture of wholesomeness in crisp polo, khakis and Boy Scout ring—had availed himself of a generic spray bottle. The circuit, a radio oscillator, glistened atop a patch of artificial grass that some postdocs had set up as an outdoorsy backdrop.
The first spritz of water caused the circuit to slowly curl, like a scrap of paper that had just caught fire. When Rogers sprayed again, the circuit hunkered and collapsed onto itself. The next sprinkles were deathblows: The circuit and its transparent silk backing shriveled into a liquid ball, which dribbled down a long blade of grass. What seconds earlier had been a functional piece of electronics with diodes, inductors and silicon transistors was now no more conspicuous—or long for this world—than a drop of morning dew.
“Yeah, it’s pretty funky,” says Rogers, who is 46 and has the earnest manner of the guy-next-door. But this was no parlor trick. Rogers and his team of researchers designed the circuit for “transience”: It was born to die. And as Rogers sees it, that could launch electronics into uncharted waters in medicine, environmental studies and national security. We may soon see sensors that track blood pressure in the aorta after heart surgery, then dissolve once a patient is out of the woods. Or a nontoxic cellphone we flush down the drain on purpose when we’re ready for an upgrade. Or sensitive battlefield technology that goes plop-plop-fizz-fizz before it falls into enemy hands. “Our hope is there’s a lot of value in this,” he says. “It’s not just a curiosity.”
Transient electronics may be the most mind-bending invention yet to come out of Rogers’ lab, an idea factory whose rate of publication in major scientific journals is matched only by its output of headline-grabbing gizmos. Rogers, who holds one of the university’s loftiest chairs, has appointments in five departments. He also directs the school’s Frederick Seitz Materials Research Laboratory. He authors or co-authors dozens of articles most years, many for marquee journals like Science and Nature. But his lab, for all its serious science, could just as easily be a back lot for the Bionic Man.
Rogers and his collaborators have built cellophane-like sheaths of electronics that wrap the undulating surfaces of the heart. They have made eyeball-shaped cameras that mimic human and insect sight, and soft threads of tiny LEDs that can be injected right into the brain. During my visit, a postdoc showed me a transistor-infused temporary skin tattoo—“epidermal electronics”—that could free hospital patients from the tangle of wires and clip-on sensors that keep doctors abreast of vital signs.
Rogers rose to stardom in the scientific world not just for dreaming up these ideas, but also for puzzling out how to build them. Many of his insights are the product of a studied disregard for status quo notions about silicon-based circuits.
Rigidity, stiffness and durability are the cornerstones of modern electronics. They are embedded into its very vocabulary: microchip, solid state, circuit board. For 90 percent of the things electronics do today, that may be fine. Rogers is interested in the other 10 percent: He wants to make hardware soft—soft enough for the moving, swelling and pulsing contours of the human body and natural world. His target is nothing less than the border between man and machine. The brain “is like Jell-O, and it’s time-dynamic, and moving around,” Rogers says. “A silicon chip is completely mismatched in geometry and mechanics, and it can’t accommodate motion without constraining that motion.”
Sure, an electronic probe can be sunk into brain tissue. “But now you have a needle in a bowl of Jell-O that’s sloshing around.” Who’d want that?
For a short time, Rogers, like other researchers, saw plastic circuits as the solution. But plastic’s flexibility came at what turned out to be a great cost: Electrically it was 1,000 times slower than silicon, the superstar of semiconductors. “You couldn’t do anything requiring sophisticated, high-speed operation,” he says.