Though not quite a reality yet, this scenario isn’t too far off. In addition to dissolvable electronics, scientists have now built a biodegradable remote-controlled, power-harvesting circuit, described May 17 in Advanced Materials, and are already testing absorbable thermal electronics in rodents.

This biocompatible remote-controlled circuit is an important step toward building dissolvable electronics that could function as “electroceuticals,” devices that perform therapeutic roles and then disappear. Such roles could include stimulating nerve and bone growth, helping heal wounds, delivering drugs, or acting as antibiotics.

“In each case, the device needs to function only for a timeframe set by a healing process. As such, the ideal scenario is for the device to simply disappear afterward,” said John Rogers, a mechanical engineer at the University of Illinois. Last year, Rogers described the development of a water-soluble, silicon-based circuit that completely dissolves in water; earlier this year, his team produced tiny LEDs that can be injected into the brain.

The remote-controlled circuits are fashioned on super-thin silk and are responsive to radio frequencies. The team builds the capacitors, inductors, and resistors using water-soluble and biocompatible materials: silicon nanomembranes, which work as semiconductors; magnesium, which already plays an important role in biological systems; silicon dioxide or magnesium oxide as insulators; and silk, for the substrate upon which the circuits are crafted.



The system’s antenna — a crucial component for receiving the radio signals used to power the device — is made by layering magnesium onto silk. An ultra-thin version, with a 500-nm thick magnesium antenna, completely dissolves after two hours in deionized water at room temperature. A version that’s six times thicker can take a few days to dissolve.

To demonstrate the functionality of the device, Rogers and his colleagues built a power-harvesting circuit that attached the magnesium-on-silk antenna to an LED. When they switched on a radio transmitter placed as far as 6 feet away, the device converted about 15 percent of the radio waves it received into electrical energy, and the light blinked on. Then, when they placed the circuit in deionized water, it dissolved.

The work is well done and is an important step toward realizing biodegradable electronic systems, said Christopher Bettinger, a polymers engineer at Carnegie Mellon University. Bettinger notes that using radio as a power source means that devices meant to be implanted deeper will need bigger antennas. “I think the power source is going to be the real issue with biodegradable electronics,” he said. “There are many great applications, but defining the specific disease or indication where biodegradable electronics has specific advantage will also be a key part of the broader strategy.”

Now, Rogers and his colleagues are testing a device capable of delivering thermal therapy in rodents. They’ve implanted the ephemeral electronics in approximately 100 mice so far, just beneath the skin. Using an infrared camera, the scientists can monitor whether the devices are working. When they are, they raise the temperature at the implant site by just a few degrees. And so far, Rogers says, there have been “no signs of inflammation, fibrosis, or any other kind of adverse reaction,” throughout the course of surgical implantion and resorption.