Engineers have developed a neural implant that can be both programmed and charged remotely with a magnetic field. The integrated microsystem — MagNI (magnetoelectric neural implant) — incorporates magnetoelectric transducers that allow the chip to harvest power from an alternating magnetic field outside the body.
MagNI targets applications that require programmable, electrical stimulation of neurons; for instance, to help patients with epilepsy or Parkinson’s disease. The device integrates magnetoelectric transducers with CMOS (complementary metal-oxide semiconductor) technologies to create a bioelectronic platform for many applications.
Tissues do not absorb magnetic fields as they do other types of signals and will not heat tissues like electromagnetic and optical radiation or inductive coupling. Ultrasound doesn’t have the heating issue but the waves are reflected at interfaces between different mediums like hair and skin or bones and other muscle. Because the magnetic field also transmits control signals, MagNI is also calibration-free, robust, and does not require any internal voltage or timing reference.
Components of the prototype device sit on a flexible polyimide substrate with only three components: a 2 × 4-millimeter magnetoelectric film that converts the magnetic field to an electric field, a CMOS chip, and a capacitor to temporarily store energy. The team successfully tested the chip’s long-term reliability by soaking it in a solution and testing in air and jellylike agar, which emulates the environment of tissues.
In the current generation of chips, energy and information flow only one way but the team is working on two-way communication strategies to facilitate data collection from implants and enable more applications.