Electronic devices dissolve in body as if by magic

Scientists have designed and tested “transient” circuits which vanish harmlessly after controlled amounts of time.

In future, they could be used to create devices for monitoring heart or brain activity, delivering drugs, or killing bacteria with heat.

Unlike medical implants used today, they would do their job and then be fully absorbed by the body with no long-term ill effects.

Other applications include “green” components for mobile phones and laptops that will never end up in landfill sites.

Environmental sensors made from transient electronics could also be placed on roads or buildings without having to be retrieved afterwards.

A number of functional vanishing devices have been tested in the laboratory, including temperature and strain sensors, light detectors, solar cells, simple radio transmitters, and even a 64 pixel digital camera.

Some circuits were also surgically implanted in rats and mice.

One, placed in a rat, successfully fought off infection of a wound by killing bacteria with heat.

Professor Fiorenzo Omenetto, a leading member of the team from Tufts School of Engineering in Medford, US, said: “These devices are the polar opposite of conventional electronics whose integrated circuits are designed for long-term physical and electronic stability.

“Transient electronics offer robust performance comparable to current devices but they will fully resorb into their environment at a prescribed time, ranging from minutes to years, depending on the application.

“Imagine the environmental benefits if cell phones, for example, could just dissolve instead of languishing in landfills for years.”

The secret to the magic trick is silk.

Components made of magnesium and silicon are wrapped in ultra-thin sheets of protein from silkworm cocoons, whose structure determines how long it takes for the whole device to degrade.

Silicon wafers used in conventional electronics would take hundreds of years to be absorbed into the body.

But the ultra-thin silicon “nanomembranes” used in the vanishing circuits disappear in a few days or weeks depending on their thickness.