The first neural implant that can be charged, programmed, and controlled remotely using a magnetic field has been developed by US scientists. The device was described in detail at the International Solid-State Circuits Conference in February in San Francisco. Programmable electrical stimulation of neurons with such a device might be used in novel treatments for epilepsy or Parkinson's disease.

Rice University engineers Kaiyuan Yang, Jacob Robinson, Zhanghao Yu, Joshua Chen, Yan He, Amanda Singer, and Benjamin Avants, developed the integrated microsystem, a MagNI (for magnetoelectric neural implant), to incorporate magnetoelectric transducers that can harvest energy from an external alternating magnetic field.

"This is the first demonstration that you can use a magnetic field to power an implant and also to program the implant," explains Yang. "By integrating magnetoelectric transducers with CMOS (complementary metal-oxide semiconductor) technologies, we provide a bioelectronic platform for many applications. CMOS is powerful, efficient and cheap for sensing and signal processing tasks." MagNI has numerous benefits over conventional stimulation technology, even ultrasound, electromagnetic radiation, inductive coupling, and optical technologies. Moreover, tissues do not absorb magnetic fields so they are neither heated nor harmed by them.

The prototype device is built on a flexible polyimide substrate with only three components: a 2-by-4-millimeter magnetoelectric film that converts the magnetic field to an electric field, the CMOS chip and a capacitor to store energy transiently. It is calibration free and needs no internal voltage to operate. The team has tested the device in air and in simulated physiological conditions using agar gel and found it to be reliable in the long term.

The team has also tested the device in a small organism, Hydra vulgaris, exciting it under constrained conditions in a microfluidic device. They could observe fluorescent signals associated with contractions in the creature triggered by contact with the MagNI. The researchers are now testing it in vivo with other models. Given that information flow in this prototype is one-way, the next step will be to incorporate sensor technology to close the feedback loop for a wider range of applications.

Details of the research will be made available in a paper entitled "An 8.2 mm3 Implantable Neurostimulator with Magnetoelectric Power and Data Transfer," in the IEEE Xplore Digital Library.