Implants in the future may be low-cost, and capable of functioning while in direct contact with living tissue inside the body.
Most existing silicon-based electronics experience interference when implanted inside the body, due to interactions between electrolytes and the electrical signals within the circuits.
Electrolytes such as sodium and potassium control nerves and muscles and maintain hydration. They carry positive or negative electric charges. These charged states lead to silicon absorbing them, causing interference with the circuit’s electronic behaviour.
Looking to improve the bio-compatibility of existing and affordable silicon electronics, researchers at the Ohio State University developed an aluminium oxide coating which blocks the electrolytes from entering the silicon.
Silicon circuits that had been coated with the aluminium oxide layer continued to function in laboratory tests, even after 24 hours of immersion in a solution that mimicked typical body chemistry. This means sensors made with silicon and coated with this material can work even when directly touched by blood, bodily fluids and tissue.
The first application will be an insertable sensor which detects the presence of proteins that mark the first signs of organ rejection in the body.
Doctors would insert a needle populated with sensors into the patient's body near the site of the implanted organ, in order to detect the protein, and using that information, tailor the patient's dosage of anti-rejection drugs.
This is the first step toward fabricating devices that could be implanted in the body long-term. Other coating materials may also be possible, such as titanium-based layers. Future use for coated polymer semiconductors would also include use as nerve replacements.