Magnetoelectric materials for miniature, wireless neural stimulation at therapeutic frequencies

Abstract

A fundamental challenge for bioelectronics is to deliver power to miniature devices inside the body. Wires are common failure points and limit device placement. On the other hand, wireless power by electromagnetic or ultrasound waves must overcome absorption by the body and impedance mismatches between air, bone, and tissue. In contrast, magnetic fields suffer little absorption by the body or differences in impedance at interfaces between air, bone, and tissue. These advantages have led to magneticallypowered stimulators based on induction or magnetothermal effects. However, fundamental limitations in these power transfer technologies have prevented miniature magnetically-powered stimulators from applications in many therapies and disease models because they do not operate in clinical "highfrequency" ranges above 50 Hz. Here we show that magnetoelectric materials -applied in bioelectronic devices -enable miniature magnetically-powered neural stimulators that can operate up to clinically-relevant high-frequencies.As an example, we show that ME neural stimulators can effectively treat the symptoms of a hemi-Parkinson's disease model in freely behaving rodents. We further demonstrate that ME-powered devices can be miniaturized to mmsized devices, fully implanted, and wirelessly powered in freely behaving rodents. These results suggest that ME materials are an excellent candidate for wireless power delivery that will enable miniature bioelectronics for both clinical and research applications.

Over the Horizon: The Present and Future of Endovascular Neural Recording and Stimulation

“…Magnetoelectric (ME) materials provide another alternative. Here, a voltage is generated by mechanical coupling between magnetostrictive and piezoelectric layers in a thin film (Wickens et al, 2018). The benefit compared to induction is that a significantly smaller implant can be used that requires much weaker magnetic fields.…”

“…The benefit compared to induction is that a significantly smaller implant can be used that requires much weaker magnetic fields. Wickens et al (2018) used ME stimulators placed the subthalamic nucleus to apply a biphasic 200 Hz stimulus and noted significant changes in behavior of hemi-parkinsonian rats. Rice-sized ME stimulators were developed for a human model with a corresponding magnetic stimulation coil being worn around the head (Wickens et al, 2018).…”

“…Wickens et al (2018) used ME stimulators placed the subthalamic nucleus to apply a biphasic 200 Hz stimulus and noted significant changes in behavior of hemi-parkinsonian rats. Rice-sized ME stimulators were developed for a human model with a corresponding magnetic stimulation coil being worn around the head (Wickens et al, 2018). Future miniaturized ME stimulators may be more flexible and navigable, enabling deployment within blood vessels.…”

Developing Next-Generation Brain Sensing Technologies—A Review

“…Active CMOS arrays can also be created by thinning silicon CMOS down to thicknesses below 15 mm, rendering these devices flexible and pliable [29]. Ultra-small wireless implants generally require other energy modes for communication and telemetry at depth, including ultrasound [30]- [32], or magnetic fields [33].…”

Wearable wireless power systems for ‘ME-BIT’ magnetoelectric-powered bio implants

“…Several methods are proposed in the literature including acoustic [ 14 ], electromagnetic [ 15 ], [ 16 ], and magnetic technologies with the latter comprising magnetothermal [ 17 ], [ 18 ], magnetoelectric(ME) [ 19 ]–[ 21 ], and inductive coupling [ 22 ]. While there are advantages to each approach, the physics of wireless data and power transfer imposes performance trade-offs [ 23 ].…”