Scientists at the Massachusetts Institute of Technology (MIT) have created a groundbreaking antenna so small it can be injected into the body through a needle.
Despite being only about the size of a grain of sand, this new device can wirelessly power medical implants deep inside the body—potentially eliminating the need for bulky batteries or invasive surgeries.
Developed by researchers in the MIT Media Lab’s Nano-Cybernetic Biotrek group, the antenna represents a major step toward truly miniature, battery-free medical implants.
These could include heart pacemakers, brain stimulators for Parkinson’s disease or epilepsy, and even glucose monitors for people with diabetes.
The work was recently published in IEEE Transactions on Antennas and Propagation.
“This is the next major step in miniaturizing deep-tissue implants,” said Baju Joy, a Ph.D. student at the Media Lab and co-author of the study. “It enables battery-free implants that can be placed with a needle instead of major surgery.”
At present, most deep-tissue medical implants are powered in one of two ways. Some use a battery several centimeters long, which must be surgically implanted and later replaced.
Others rely on a larger magnetic coil that sits just beneath the skin and wirelessly transmits power.
But shrinking these coils to smaller sizes causes them to work only at very high frequencies, which can overheat nearby tissue—a dangerous side effect that limits how much power can be safely delivered.
The MIT team overcame this challenge by designing an antenna that can operate safely at low frequencies. Their device, just 200 micrometers wide, uses an innovative combination of materials: a magnetostrictive film that bends when exposed to a magnetic field, and a piezoelectric film that converts that movement into an electric current.
“When a magnetic field is applied, the magnetic layer vibrates and transfers its motion to the piezoelectric layer, which generates electric charges,” Joy explained. “We’re basically turning magnetic energy into electrical energy through vibration.”
This new mechanism allows the antenna to work efficiently at a much lower frequency—around 109 kilohertz—avoiding the heating problem and delivering significantly more power than existing miniature antennas.
In fact, it can generate 10,000 to 100,000 times more power than other implantable antennas of similar size.
“This technology opens a new avenue for minimally invasive bioelectronic devices that can operate wirelessly deep inside the human body,” said Professor Deblina Sarkar, the study’s senior author and head of the Nano-Cybernetic Biotrek group.
The external magnetic field that powers the antenna can be produced by a small device similar to a wireless phone charger. It could be worn as a skin patch or kept in a pocket close to the body, transmitting energy safely to the internal implant.
Another advantage is that the antenna can be built using the same manufacturing techniques used for microchips. This means it could be mass-produced at low cost and easily integrated with existing electronics like sensors and electrodes.
Because the entire system is so small, it can be injected through a needle, allowing doctors to place multiple antennas in the body to treat larger or multiple areas.
Possible applications go far beyond powering pacemakers or brain implants. For example, a future glucose sensor could be paired with one of these antennas to monitor blood sugar levels continuously—without requiring a bulky device or frequent replacements.
“This is just one example,” Joy said. “We can integrate this antenna technology with many other existing micro-scale systems, enabling a whole new generation of medical implants that are smaller, safer, and much easier to place.”
