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December 2009

Silicon-silk electronics for the body

Researchers have made electronics that almost completely dissolve inside the body by building thin, flexible silicon electronics on silk substrates.

The research group, which includes researchers from University of Pennsylvania and University of Illinois at Champaign-Urbana, has demonstrated arrays of transistors made on thin films of silk, according to Technology Review. While electronics usually must be encased to protect them from the body, these electronics do not need protection, and the silk means the electronics conform to biological tissue. The silk melts away over time, and the thin silicon circuits left behind do not cause irritation because they are just nanometers thick.

Source: Technology Review

“Current medical devices are very limited by the fact that the active electronics have to be ‘canned,’ or isolated from the body, and are on rigid silicon,” said Brian Litt, associate professor of neurology and bioengineering at the University of Pennsylvania. Litt, who is working with the silk-silicon group to develop medical applications for the new devices, said they could interact with tissues in new ways. The group is developing silk-silicon LEDs that might act as photonic tattoos that can show blood-sugar readings, as well as arrays of conformable electrodes that might interface with the nervous system.

Last year, John Rogers, professor of materials science and engineering at the Beckman Institute at the University of Illinois at Champaign-Urbana, developed flexible, stretchable silicon circuits whose performance matches that of their rigid counterparts. To make these devices biocompatible, Rogers’s lab collaborated with Fiorenzo Omenetto and David Kaplan, professors of bioengineering at Tufts University in Medford, Mass., who last year reported making nanopatterned optical devices from silkworm-cocoon proteins.

To make the devices, silicon transistors about 1 millimeter long and 250 nanometers thick are collected on a stamp and then transferred to the surface of a thin film of silk. The silk holds each device in place, even after the array is implanted in an animal and wetted with saline, causing it to conform to the tissue surface.

The group is currently designing electrodes built on silk as interfaces for the nervous system. Electrodes built on silk could, Litt said, integrate much better with biological tissues than existing electrodes, which either pierce the tissue or sit on top of it.