These electronics can monitor the brain, then dissolve and vanish
From pacemakers to insulin pumps, electronic implants are a powerful medical tool, but they present their own suite of risks — scarring, rejection and sepsis among them. Now a team of researchers has created a dissolving electronic implant, sort of like a much more sophisticated version of dissolving sutures. Sutures, however, can’t be injected into a rat’s brain, and don’t come equipped with temporary Wi-Fi.
The research team is calling the implantable chips “bioresorbable.” These tiny chips are biodegradable in the fluid environment of a living creature: They dissolve after a few days. The chips are made of biologically inert materials like silicon, or similar materials that won’t cause an immune response or an overdose. In rats, the researchers successfully implanted microchips that measured temperature and pressure from inside the brain. That kind of information is critical for monitoring swelling and inflammation as patients recover from a brain injury or surgery.
The experimental setup, with embedded WiFi.
These dissolving implantable microchips are made out of tiny, flexible piezoresistive sensors. Under mechanical forces, the electrical resistance of the sensor body changes, which allows them to function as reliable pressure sensors. Piezoresistive sensors are also exquisitely dependent on temperature, so they make sensitive implantable thermometers. The sensor is connected to a flake of silicon sufficient to parse and transmit the information through molybdenum wires that run to a little wireless transmitter module implanted below the skin. The whole sensor chip is coated with silicon, magnesium (of which we have an RDA, or Recommended Daily Allowance of about eight of these chips per day) and a dissolvable copolymer called PLGA that we’re already using in other medical devices.
A polymer coat keeps the chip from dissolving immediately, but wears away over time.
As a proof of concept, the chips stayed viable in various rat body cavities and fluids including cerebrospinal fluid for several days, while the rats ambled freely around their habitats. Longevity of the implant is, in part, a function of the thickness of the coating: the thicker the coating, the longer the chip takes to dissolve. Researchers are hoping to make versions of these bioresorbable implants that can last for much longer — perhaps the whole duration of a patient’s treatment.
Sensors of this sort have the potential to revolutionize patient treatment. While we have medical technologies that allow us to image what’s going on inside a body, our ability to directly observe the internal organs is limited by many factors. Microscopic sensors that can report shifts in temperature and pressure could map the damaged areas of a stroke victim’s brain far more accurately than any technology we have today.