Neural implants may provide treatment options for a wide variety of ailments, including Parkinson’s and epilepsy, but such devices have to work for long periods of time in a very difficult environment inside the cranium. One challenge is providing power to brain implants and another is communicating with such implants to control their function. Currently, this is typically achieved using wires, but wires that cross tissues and penetrate to the outside are extremely problematic for a variety of reasons. Now, engineers at Rice University have just unveiled a neural implant that can be powered and programmed using an external magnetic field. The technology, presented at the International Solid-State Circuits Conference in San Francisco, may overcome some of the most troubling and limiting aspects of current brain-computer interfaces, stimulators, and other neural implants. The new device, called MagNI (magnetoelectric neural implant), uses magnetoelectric transducers to convert a quickly changing magnetic field into an electric current. A belt or other device strapped to the body near where the implant is can therefore be used to power the implant. The same approach is used to deliver signals to the device that the implant can use to program itself. “This is the first demonstration that you can use a magnetic field to power an implant and also to program the implant,” said Kaiyuan Yang, one of the developers of the device, in a Rice press release. “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.” The advantage of using magnetic fields to power and control the implant is that they do not cause heating of tissues as much as optical radiation or inductive coupling, for example. Compared with ultrasound, the signal retains its fidelity a lot better and therefore can be used to program a device implanted deep inside the body. The device is made of three parts, including a magnetoelectric film that performs the magnetism to electricity conversion, a CMOS chip, and an electric storage capacitor. So far it has been tested in a lab to excite Hydra vulgaris, an animal resembling an octopus, but more in vivo tests are on the way that will involve animals closer to humans. Additional work will be needed to allow such an implant to stream data from inside the body, allowing for the two-way communication required for smart implants. Source
