Design and Implementation of a Passive Neurostimulator with Wireless Resonance-Coupled Power Delivery and Demonstration on Frog Sciatic Nerve and Gastrocnemius Muscle

The thesis presented has four goals: to perform a comprehensive literature review on current neurostimulator technology; to outline the current issues with the state-of-the-art; to provide a neurostimulator design that solves these issues, and to characterize the design and demonstrate its neurostimulation features. The literature review describes the physiology of a neuron, and then proceeds to outline neural interfaces and neurostimulators. The neurostimulator design process is then outlined and current requirements in the field are described. The novel neurostimulator circuit that implements a solution that has wireless capability, passive control, and small size is outlined and characterized. The circuit is demonstrated to operate wirelessly with a resonance-coupled multi-channel implementation, and is shown powering LEDs. The circuit was then fabricated in a miniature implementation which utilized a 10 x 20 x 3 mm&179 antenna, and occupied a volume approximating 1 cm&179. This miniature circuit is used to stimulate frog sciatic nerve and gastrocnemius muscle in vitro. These demonstrations and characterization show the device is capable of neurostimulation, can operate wirelessly, is controlled passively, and can be implemented in a small size, thus solving the aforementioned neurostimulator requirements. Further work in this area is focused on developing an extensive characterization of the device and the wireless power delivery system, optimizing the circuit design, and performing in vivo experiments with restoration of motor control in injured animals. This device shows promise to provide a comprehensive solution to many application-specific problems in neurostimulation, and be a modular addition to larger neural interface systems

Neurostimulator with Waveforms Inspired by Nature for Wearable Electro-Acupuncture

The work presented here has 3 goals: establish the need for novel neurostimulation waveform solutions through a literature review, develop a neurostimulation pulse generator, and verify the operation of the device for neurostimulation applications. The literature review discusses the importance of stimulation waveforms on the outcomes of neurostimulation, and proposes new directions for neurostimulation research that would help in improving the reproducibility and comparability between studies. The pulse generator circuit is then described that generates signals inspired by the shape of excitatory or inhibitory post-synaptic potentials (EPSP, IPSP). The circuit analytical equations are presented, and the effects of the circuit design components are discussed. The circuit is also analyzed with a capacitive load using a simplified Randles model to represent the electrode-electrolyte interface, and the output is measured in phosphate-buffered saline (PBS) solution as the load with acupuncture needles as electrodes. The circuit is designed to be used in different types of neurostimulators depending on the needs of the application, and to study the effects of varying neurostimulation waveforms. The circuit is used to develop a remote-controlled wearable veterinary electro-acupuncture machine. The device has a small form-factor and 3D printed enclosure, and has a weight of 75 g with leads attached. The device is powered by a 500 mAh lithium polymer battery, and was tested to last 6 hours. The device is tested in an electro-acupuncture animal study on cats performed at the Louisiana State University School of Veterinary Medicine, where it showed expected electro-acupuncture effects. Then, a 2-channel implementation of the device is presented, and tested to show independent output amplitude, frequency, and stimulation duration per channel. Finally, the software and hardware requirements for control of the wearable veterinary electro-acupuncture machine are detailed. The number of output channels is limited to the number of hardware PWM timers available for use. The Arduino software implements PWM control for the output amplitude and frequency. The stimulation duration control is provided using software timers. The communications protocol between the microcontroller board and Android App are described, and communications are performed via Bluetooth