Early Steps Toward the Development of a Wireless Neurostimulator Powered and Controlled by Radio Waves
Brain-machine interfaces communicate data from the brain to external devices to monitor patient health during procedures, such as deep brain stimulation for Parkinson’s disease and in medical research. The lack of safe and long lasting implantable devices hampers the improvement of brain-machine interfaces and deep brain stimulation for research and patient therapies. In this paper, we describe the first steps towards a wirelessly-powered and controlled neural and motor tissue stimulator. We constructed a wireless, external-stimulation device using a tank circuit and stimulation leads. We quantified the relationship between radio-frequency (RF) source-distance and strength-of-voltage-output to determine if the stimulator was powered and controlled by Ultra High Frequency (UHF) and far-field coupling or Very High Frequency (VHF) and near-field coupling. We then implanted the stimulation leads in a cricket leg and tracked the physical motion of a cricket leg in response to stimulation from the device. Our findings suggest the device used VHF to induce near-field inductive coupling to power the circuit and stimulate excitable tissue. Given that our device is powered by VHF waves, the stimulator requires relatively large antennas, which limit the miniaturization of the device. Additionally, VHF waves power and control the voltage emitted from all stimulation leads connected to one device. This prohibits emission of different voltages from different stimulations leads. The lack of voltage specificity hinders clinical and research uses. Future studies should further the miniaturizing of the device, creating a frequency-discriminatory system to stimulate one stimulation lead at a consistent determinable voltage, and determining the efficacy of VHF transmission through biological tissue.
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