Implantable Silicon-Silk Electronics at technologyreveiw.com

Duane pointed me in this direction......

http://www.technologyreview.com/computing/23847/page1/

By building thin, flexible silicon electronics on silk substrates, researchers have made electronics that almost completely dissolve inside the body. So far the research group has demonstrated arrays of transistors made on thin films of silk. While electronics must usually be encased to protect them from the body, these electronics don't 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 don't cause irritation because they are just nanometers thick.

lots more interesting stuff to be found at http://www.technologyreview.com/
like biodegrable transistors http://www.technologyreview.com/biomedicine/23940/
or 'rapid prototyping in biology'
http://www.technologyreview.com/biomedicine/23567/

Silicon on silk: This clear silk film, about one centimeter squared, has six silicon transistors on its surface. These flexible devices can be implanted in mice like the one in this image without causing any harm, and the silk degrades over time. The orange liquid on the hair is a disinfectant used during the surgery