AUTHOR=Freeman Daniel K. , O'Brien Jonathan M. , Kumar Parshant , Daniels Brian , Irion Reed A. , Shraytah Louis , Ingersoll Brett K. , Magyar Andrew P. , Czarnecki Andrew , Wheeler Jesse , Coppeta Jonathan R. , Abban Michael P. , Gatzke Ronald , Fried Shelley I. , Lee Seung Woo , Duwel Amy E. , Bernstein Jonathan J. , Widge Alik S. , Hernandez-Reynoso Ana , Kanneganti Aswini , Romero-Ortega Mario I. , Cogan Stuart F. 

TITLE=A Sub-millimeter, Inductively Powered Neural Stimulator

JOURNAL=Frontiers in Neuroscience

VOLUME=Volume 11 - 2017

YEAR=2017

URL=https://www.frontiersin.org/journals/neuroscience/articles/10.3389/fnins.2017.00659

DOI=10.3389/fnins.2017.00659

ISSN=1662-453X

ABSTRACT=Wireless neural stimulators are being developed to address problems associated with traditional lead-based implants. However, designing wireless stimulators on the sub-millimeter scale (<1mm3) is challenging. As device size shrinks, it becomes difficult to deliver sufficient wireless power to operate the device. Here, we present a sub-millimeter, inductively powered neural stimulator consisting only of a coil to receive power, a capacitor to tune the resonant frequency of the receiver, and a diode to rectify the radio-frequency signal to produce neural excitation. By  replacing any complex receiver circuitry with a simple rectifier, we have reduced the required voltage levels that are needed to operate the device from – 0.5 - 1V (e.g. for CMOS) to approximately 0.25 – 0.5V. This reduced voltage allows the use of smaller receive antennas for power, resulting in a device volume of 0.3 – 0.5mm3. The device was encapsulated in epoxy, and successfully passed accelerated lifetime tests in 80°C saline for two weeks. We demonstrate a basic proof-of-concept using stimulation with tens of microamps of current delivered to  the sciatic nerve in rat to produce a motor response. The device is designed to operate in tissue up to approximately 5cm depth.