11/16/2009
Mating man and machine may be closer than we think. As an extension of their earlier work with flexible, bendable, and stretchable electronics, an Illinois team, in collaboration with researchers at Tufts University, have developed a new class of implantable biomedical devices based on ultrathin, ultrasmall silicon electronic devices mounted on silk substrates that completely resorb inside the body over time.
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Mating man and machine may be closer than we think. As an extension of their earlier work with flexible, bendable, and stretchable electronics, an Illinois team, in collaboration with researchers at Tufts University, have developed a new class of implantable biomedical devices based on ultrathin, ultrasmall silicon electronic devices mounted on silk substrates that completely resorb inside the body over time.
“Advanced implantable biomedical devices have great potential in clinical applications, but achieving biocompatibility can be challenging, due to the complex nature of the biological response to many organic and inorganic materials,” explained John A. Rogers, who is the Lee J. Flory-Founder Chair in Engineering Innovation and a professor of materials science and engineering at Illinois. “Electronic devices made to be implanted in the body are usually encased to protect them. We’ve taken a different approach, in which a major portion of the electronics is simply consumed by the body, as their function in monitoring or healing is no longer needed.”
According to Rogers, the silk melts away over time and the thin silicon circuits left behind don't cause irritation because they are just nanometers thick. This approach avoids some of the longer term challenges in biocompatibility since some parts or all of the system resorbs in the body over time. The small amount of material remains that its induced biological response is negligible.
In a paper published in the journal Applied Physics Letters, the researchers noted that silk is attractive, compared to other biodegradable polymers, because of its robust mechanical properties, the ability to tailor the dissolution and/or bioresorption rates from hours to years, the formation of non-inflammatory amino acid degradation products, and the option to prepare the materials at ambient conditions to preserve sensitive electronic functions.
“This dissolution process relies on the capability of silk to disintegrate in water, leaving proteins as the products that are then degraded by proteolytic activity,” Rogers said. The resulting silk fibroin protein is a Food and Drug Administration (FDA) approved biocompatible material that generates non-inflammatory amino acid degradation products usable in cell metabolic functions. Further, the mechanical properties of the silk substrate can be tailored, based on the mode of processing, to match the level of toughness required.
So far the research group has demonstrated arrays of transistors made on thin films of silk. To make these devices biocompatible, Rogers's research team collaborated with Fiorenzo Omenetto and David Kaplan, professors of biomedical engineering at Tufts University and experts in the materials science and processing of silk. Largely used for biomedical applications such as tissue engineering, silk has recently found itself respun into a platform material for high technology.
“The favorable combination of material properties and all-water based processing allows for unusual applications where photonics and optoelectronics meet with biology and medicine” says Omenetto, who last year reported making nanopatterned optical devices from silkworm-cocoon proteins.
The Rogers' Research Group is also working with colleagues at the University of Pennsylvania on several biomedical applications such as silk-silicon LEDs that might act as photonic tattoos that can show blood-sugar readings, and arrays of conformable electrodes that can interface with the nervous system.
Rogers is affiliated with the Department of Electrical and Computer Engineering, the Department of Mechanical Science and Engineering, the Department of Chemistry, the Frederick Seitz Materials Research Laboratory, and the Micro and Nanotechnology Laboratory at Illinois. In September, Rogers was named a 2009 MacArthur Fellow by the John D. and Catherine T. MacArthur Foundation.
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Contact: John Rogers, Department of Materials Science and Engineering, 217/244-4979.
If you have any questions about the College of Engineering, or other story ideas, contact Rick Kubetz, Engineering Communications Office, 217/244-7716, writer/editor.