magnetic powered neural simulator

https://medicalxpress.com/news/2020-06-rice-team-tiny-magnetically-powered.html

 

Rice University neuroengineers have created a tiny surgical implant that can electrically stimulate the brain and nervous system without using a battery or wired power supply.

The neural stimulator draws its power from magnetic energy and is about the size of a grain of rice. It is the first magnetically powered neural stimulator that produces the same kind of high-frequency signals as clinically approved, battery-powered implants that are used to treat epilepsy, Parkinson's disease, chronic pain and other conditions.

The implant's key ingredient is a thin film of "magnetoelectric" material that converts magnetic energy directly into an electrical voltage. The method avoids the drawbacks of radio waves, ultrasound, light and even magnetic coils, all of which have been proposed for powering tiny wireless implants and have been shown to suffer from interference with living tissue or produce harmful amounts of heat.

Tiny implants capable of modulating activity of the brain and nervous system could have wide-ranging implications. While battery-powered implants are frequently used to treat epilepsy and reduce tremors in patients with Parkinson's disease, research has shown that neural stimulation could be useful for treating depression, obsessive-compulsive disorders and more than a third of those who suffer from chronic, intractable pain that often leads to anxiety, depression and opioid addiction.

Singer, an applied physics student in Robinson's lab, solved the wireless power problem by joining layers of two very different materials in a single film. The first layer, a magnetostrictive foil of iron, boron, silicon and carbon, vibrates at a molecular level when it's placed in a magnetic field. The second, a piezoelectric crystal, converts mechanical stress directly into an electric voltage.

"The magnetic field generates stress in the magnetostrictive material," Singer said. "It doesn't make the material get visibly bigger and smaller, but it generates acoustic waves and some of those are at a resonant frequency that creates a particular mode we use called an acoustic resonant mode."

Robinson said the magnetoelectric films harvest plenty of power but operate at a frequency that's too high to affect brain cells. "A major piece of engineering that Amanda solved was creating the circuitry to modulate that activity at a lower frequency that the cells would respond to," Robinson said. "It's similar to the way AM radio works. You have these very high-frequency waves, but they're modulated at a low frequency that you can hear."

Singer said creating a modulated biphasic signal that could stimulate neurons without harming them was a challenge, as was miniaturization.

 

 

reference

Amanda Singer et al, Magnetoelectric Materials for Miniature, Wireless Neural Stimulation at Therapeutic Frequencies, Neuron (2020). DOI: 10.1016/j.neuron.2020.05.019