Second skin
    Illustration by Sarah Lowe / North by Northwestern

    A temporary tattoo of a grizzled pirate, clamping a sword in his mouth and sporting a ragged blue hat, leers at readers from the pages of September’s issue of Science. 

    The article isn’t about advances in treasure map technology, in mid-size Bay Area football franchises or even in third grade birthday party clean-up. Instead, the article, “Epidermal Electronics,” describes what the privateer tattoo can hide: a very small, very thin medical sensor. 

    Researchers at Northwestern and other institutions have figured out how to condense many kinds of electronics so that they’re both as thin and malleable as skin. These condensed electronics can include solar cells, wireless coils and, most importantly, medical sensors like EEGs and EKGs, which monitor brain and heart activity, respectively. The sensors can transmit data wirelessly at short distances to stations, computers or cell phones.

    “That is what we’ve achieved: something as flexible as skin, without using glue,” says Dr. Yonggang Huang, the Joseph Cummings Professor of Mechanical Engineering at Northwestern.

    Huang helped lead research on the project. As he sits in his office, he smiles and talks quickly, lifting objects off his desk as examples and describing one life-changing application after another. The small, thin sensors, he says, may be able to save children from Sudden Infant Death Syndrome, or SIDS, a mysterious condition in which children die in their sleep without warning.

    “Often when [SIDS is] discovered now, it’s too late,” Huang says. “But if there was something on the baby’s forehead to monitor brain signals, it could send a signal to something which would dial an ambulance and get help.” 

    The sensors could prevent a trip to the hospital too, he says. Now when someone becomes suddenly sick, emergency medical workers or doctors must take their vitals. But with these new sensors, the patient could stay at home, broadcast their biomarkers to their cell phone and see if the diagnosis might be serious.

    Shrunken sensors might even let Lou Gehrig’s disease patients interact more easily with computers, banishing the clunky equipment required today.

    “If you put the sensor on your neck, it can recognize words after some training,” Huang says. “Once a sensor can register a human voice, the device can send signals out to perform tasks. We demonstrated that it understood ‘up, down, left, right.’” 

    That the sensor can be concealed with a temporary tattoo (whether skin- or pirate-colored) is part of its appeal. Current computer interfaces — whether therapeutic or not — require something to click or hold: a keyboard, a mouse, or a touchscreen. Even speech interfaces require a microphone. But the new sensor is so small it can’t even be felt by its carrier.

    The sensor might make possible, in Huang’s words, “a true human-computer interface.”

    The sensor can stick to skin without glue (and without sensation) because of the Van der Waals force, the same weak intermolecular interaction that lets geckos stick to walls and binds the human body’s cells together. Because of this force, a sheet of paper is harder to pick up off a desk than a stapler. “We wanted to make a device so thin it can really follow the skin’s roughness,” Huang says.

    And will we see the device soon — in hospitals, if not in CVS? Not really. It takes about a decade to test biotechnology for humans after researchers license it to drug companies. Dr. Huang chuckled when asked what the sensors would cost — “That would depend on the market, which is something we professors are not good at,” he says, adding that companies were interested in its many applications.

    “They want to do this; they want to explore this,” he says. 

    Huang doubts the sensor would be cheaper than current methods, saying the team hadn’t invented anything new, only improved or shrunk existing technology. The sensor isn’t designed to be reusable, either, but if a method of peeling it off that maintained its structural integrity were found, it could be.

    The sensors also can’t stay on the body for too long. Skin constantly dies and flakes to the ground, and right now, the censor blocks that process. The sensors also can’t handle sweat.

    The researchers were primarily funded by the National Science Foundation, which pays for about 20 percent of all academic science research in the U.S. (Despite Republican threats last year, the NSF’s budget was increased by $173 million for 2012.) When the technology is finally licensed, though, Northwestern will get a chunk of the potential profits.

    It’s discoveries like this that keep Northwestern functional as a research university. Professor Richard Silverman’s 1989 synthesis of the drug Lyrica funds not only the Silverman Center, a nanotechnology group within the university exploring scientific expanses, but also humanistic studies at Northwestern. When Northwestern researchers discover, humanity — and the humantities — benefit.


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