A sub-millimeter, inductively powered neural stimulator


Freeman DK, O'Brien JM, Kumar P, Daniels B, Irion RA, Shraytah L, Ingersoll BK, Magyar AP, Czarnecki A, Wheeler J, et al. A sub-millimeter, inductively powered neural stimulator. Frontiers in Neuroscience. 2017;11.
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Wireless neural stimulators are being developed to address problems associated with traditional lead-based implants. However, designing wireless stimulators on the sub-millimeter scale (\textless1mm3) 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.

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Last updated on 12/26/2017