American Society for Peripheral Nerve

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A Low-Cost, Wirelessly Powered Implantable Microcontroller for Neural Stimulation
Jacqueline J Greene, MD1; Diego L. Guarin, Ph.D2; Christopher J. Knox, BSc3; Tessa A. Hadlock, MD4; Nate Jowett, MD4
1Massachusetts Eye and Ear Infirmary / Harvard University, Boston, MA, 2Harvard University, Boston, MA, 3Facial Nerve Center - Dept. of Otolaryngology, Massachusetts Eye and Ear Infirmary, Boston, MA, 4Facial Nerve Center - Dept. of Otolaryngology, Harvard Medical School / Massachusetts Eye and Ear Infirmary, Boston, MA

Long-term neural stimulation and blockade in small animal models is challenging. Percutaneous electrodes carry risk of extrusion, infection, or loss. Commercial implantable neurostimulation devices are expensive and offer limited customization options. Herein, we employ low-cost, open-source, two-way wireless-data-transfer-enabled miniature microcontroller technology, combined with wireless power as a fully-implantable system for long-term electrophysiology and neural stimulation studies in rodents.Materials & Methods
A Bluetooth-enabled microcontroller (Simblee RFD77201 7 GPIO breakout board) was programmed in open-source software (Arduino IDE) to deliver a 2 mA catholic electrical pulses at three different frequencies (1, 5 and 10 Hz) upon wireless command to the buccal branch of the facial nerve via a bipolar nerve cuff electrode, together with continuous transfer of device voltage and temperature to an external data logger. The microcontroller was coupled to a rechargeable lithium coin cell battery linked to a magnetic induction charging coil, with components stacked and embedded in silicone for long-term implantation. Devices were implanted into Lewis rats, and continuous stimulation delivered over several weeks via intermittent wireless charging.

Device component cost was $115. Long-term stimulation, together wire wireless transfer of data was achieved over the duration of implantation. Wireless re-charging of batteries was achieved within 30 minutes. Thermography and device temperature data demonstrated no significant overheating during charging and discharging cycles.

An open-source, fully-implantable, wirelessly-powered device for long-term neural stimulation and electrophysiology studies in small rodents was designed and successfully implemented. This approach could be expanded to a vast array of similar applications via coupling of other readily available miniature sensors and actuators to the wireless-enabled microcontroller used herein.

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