A new class of electronic sensors can monitor temperature and pressure within the skull—crucial health parameters after a brain injury or surgery—then melt when they are no longer needed, eliminating the need for additional surgery to remove the monitors and reducing the risk of infection and hemorrhage.

“This is a new class of electronic biomedical implants,” says John Rogers, professor of materials science and engineering at the University of Illinois at Urbana-Champaign. He says these kinds of systems have potential across a range of clinical practices, where therapeutic or monitoring devices are implanted or ingested, perform a sophisticated function and then resorb into the body after their function is no longer necessary.

After a traumatic brain injury or brain surgery, it is critical to monitor patients for swelling and pressure on the brain. Current monitoring technology can be bulky and invasive, Rogers says, and the wires restrict patients' movement and hamper physical therapy as they recover. Because they require continuous, hard-wired access into the head, such implants also carry the risk of allergic reactions, infection and hemorrhage, and can exacerbate the inflammation they are meant to monitor.

The new devices incorporate dissolvable silicon technology developed by Rogers’ group at the university. The sensors, smaller than a grain of rice, are built on thin sheets of silicon, which are naturally biodegradable. The sheets are are configured to function normally for a few weeks, then dissolve in the body.

The sensor connects to an embeddable wireless transmitter that lies on top of the skull. Image credit: John Rogers.Rogers’ group teamed with University of Illinois materials science and engineering professor Paul Braun to make the silicon platforms sensitive to clinically relevant pressure levels in the intracranial fluid surrounding the brain. They also added a temperature sensor and connected it to a wireless transmitter roughly the size of a postage stamp. The transmitter is implanted under the skin but on top of the skull.

The researchers are moving toward human trials for this technology and extending its functionality to other biomedical applications.

“We have established a range of device variations, materials and measurement capabilities for sensing in other clinical contexts,” Rogers says. “In the near future, we believe that it will be possible to embed therapeutic function, such as electrical stimulation or drug delivery, into the same systems while retaining the essential bioresorbable character.”