Science: Vanishing Electronic Medical Implants

Scientists have developed a new class of electronics capable of degrading into their environment, reports a new study appearing in the 28 September issue of the journal Science.

Unlike most electronic devices, which are designed to last forever, the transient circuits developed by researchers at the University of Illinois, Tufts University, and Northwestern University disappear into their environment after a programmed amount of time. The technology could be useful in biomedical implants to help treat surgical infections or stimulate bone growth.

The Science researchers crafted electronic circuits from cocoon silk, thin sheets of porous silicon, and magnesium electrodes—all materials capable of disappearing or degrading into their environment.

“We selected materials familiar to the human body, such as magnesium,” lead author S.K. Huang told the Northwestern University press office. “We didn’t want to use a material the body has no experience with.”

They tested the device as a biomedical implant in mice, using it to deliver a bactericide drug to surgical wound sites in the animals. Before implantation, the research team programmed the device to resorb or degrade after a certain amount of exposure to biofluids. The researchers say resorption potentially could be triggered by heat, radiation, pH and other environmental factors in other devices.

Known as nanomembranes, the thin sheets of silicon act as the semiconductor in the devices. Conventional silicon dissolves in biofluids, but at rates that would take hundreds of years to degrade. In contrast, the ultra-thin but sturdy silicon used in this study dissolves in a few days or weeks. Examining the mice after three weeks, the researchers observed reduced infection at the surgical wound site and only faint residues of the implant.

While these results apply specifically to the use vanishing electronics in medical applications, the devices may be used to curb other types of electronic waste in the future.