John Rogers | Atlantic Photography
CHICAGO -- Stretchy, dissolvable electronics may offer a way to fully integrate health technology with the body and to reduce future electronic waste, according to John Rogers, a materials scientist and engineer who spoke at the 2014 AAAS Annual Meeting.
Rogers, who holds the Swanlund Chair at the University of Illinois at Urbana-Champaign, said in his plenary lecture that the future of electronics is not just "smaller, faster and cheaper" but also bent, stretched and meltaway.
A smart phone is "a great device if you want to put it into your pocket...but what if you wanted to melt it into your skin, or laminate it on to your brain, or wrap it around your heart?"
One aspect of integrated circuit design hasn't changed since the transistor was first introduced, Rogers explained. "There's the fact that every integrated circuit that's ever been commercially produced has been built on the rigid, planar, brittle surface of the semiconductor wafer -- silicon for the most part."
A smart phone is "a great device if you want to put it into your pocket...but what if you wanted to melt it into your skin, or laminate it on to your brain, or wrap it around your heart?" he asked.
Rogers and his colleagues have taken up the challenge of making electronics that are curvy, soft and stretchy like much of the body itself. Freed from their brittle forms, these electronics can "integrate more intimately with the skin and are suitable for continuous use in everyday life," he explained.
Silicon is brittle, but it's also an established technology with a long history of manufacture and use. So Rogers and his colleagues looked at ways to make silicon bend to their needs. They discovered a way to shave very thin, flexible ribbons of silicon, about 110 nanometers thick (about a thousand of them would fit within the width of a single hair) and place it on stretchy sheets of rubber.
The result is a material with the geometry of an accordion bellows, Rogers said, and it is "a factor of a million times softer than the intrinsic properties of this material."
Rogers and colleagues have demonstrated a way to apply electronics made from these materials to the skin with the low-tech delivery method of a child's temporary tattoo . These devices open up the possibility of using "the skin as a window into physiological health," Rogers said, who noted that they are already used to measure things like heart and skeletal muscle activity.
Rogers' lab is participating in the first human clinical trials of "smart bandages" made with the electronics to monitor wound healing, and he hopes that someday they could be used to free newborns from the enveloping tangle of wires and monitors that are used now in neonatal intensive care wards.
The team is also testing the stretchy electronics with NASCAR race driver Paulie Harraka to monitor his hydration and temperature as he drives. For applications like this, Harraka and Rogers work with the Cambridge, Massachusetts company mc10. The wearable electronics company has used some of the same technology in a partnership with Reebok to create CHECKLIGHT, a flexible strip that monitors head impacts in football and hockey players.
Rogers' team is also working on transient electronics that could dissolve in water over a matter of days. Ribboned silicon is important here as well, he explained. A 35-nanometer-thick silicon ribbon can be dissolved in just 10 days with half a milliliter of water, compared to a typical silicon wafer that is a millimeter thick and requires a dose of 10 liters of water to disappear in a thousand years.
These could be used to build diagnostic or therapeutic devices that reside inside the body temporarily, or environmental monitors that are placed in the field and break down when they are no longer needed.
The technology may someday reduce the amount of waste produced by discarded consumer electronics, Rogers suggested. "The vision would be to make a cell phone that's completely water soluble, or even if you couldn't do that, make certain components water-soluble."
His team is testing the safety of these materials placed together with human cells, but Rogers said that a typical multivitamin with magnesium and silicon already contains "3000 times more of these elements" than the dissolvable electronics.
Rogers has already done a little experiment of his own: he ate one. "It did not taste like chicken," he noted.