Test ... a rat is implanted with the new device. Photo: Beckman Institute
Electronic devices that disappear without a trace; they sound like science fiction.
But engineers have developed a range of ultra-thin electronic components, including transistors, wireless power coils, sensors, diodes and a digital camera, that can dissolve in water or bodily fluids within minutes.
The "transient electronics" could be used as medical implants that can be reabsorbed harmlessly by the body, as sensors to measure temperature changes in the environment and in consumer devices to reduce the amount of electronic waste in landfill.
The lead engineer, John Rogers, said the components were designed to dissolve within a specific timeframe, from minutes to days, or months, and potentially years.
"A medical implant that is designed to deal with potential infections from a surgical site incision is only needed for a couple of weeks," said Professor Rogers, an engineering professor at the University of Illinois. "But for a consumer electronic device, you'd want it to stick around for a year or two."
The components were made of materials found in conventional electronic circuits, such as silicon and magnesium, but manufactured into a nanomembrane that dissolved when immersed in water.
Both elements are found naturally in the environment and body.
The tiny circuits are then packaged in silk protein, collected from silkworm cocoons, which can be programmed to dissolve at a specific time and rate by altering the material's crystal structure.
As part of their testing, the team implanted a device under the skin of a mouse. After three weeks only a faint residue remained.
They also inserted an inductive coil in the form of an anti-bacterial applique under the skin of rats to reduce infection at the site of surgical incisions.
The devices also have applications as brain, heart and muscle activity monitors and for drug delivery. As environmental sensors, the circuits could monitor changes in temperature or the effects of a chemical spill.
A biomedical engineer, Fiorenzo Omenetto, who led the research, said the performance of transient electronics was comparable to conventional devices, but with the added bonus of being reabsorbed into the environment when they were no longer needed.
"Imagine the environmental benefits if cell phones, for example, could just dissolve instead of languishing in landfills for years," said Professor Omenetto, from Tufts University.
The team's designs were published in the journal Science.