Wireless Power Transfer for Implantable Neruostimulator

Abstract

Neuromodulation of the autonomic nervous system(ANS) has recently emerged as a powerful way to control body function and treat various diseases as treatments for chronic depression, headaches, epilepsy, seizures, high blood pressure, diabetes, obesity, rheumatoid arthritis. The central nervous system(CNS), which consists of spinal cord and brain, and the peripheral nervous system (PNS), which is functionally separated from them, belong to the ANS. Non-invasive methods, which have the advantage of reducing penetration damage, are not suitable for stimulating the relatively small ANS located deep area, so invasive methods are considered more suitable despite the potential for cell penetration damage. For this reason, the market for implantable medical device (IMDs) is growing every year, but the physical size of the battery in the IMD still increases invasiveness and acts as a factor that causes inflammation and discomfort to patients. In this study, we proposed the on demand manner neurostimulator that eliminates the volume of batteries by designing ultra-small antennas using wireless power transfer(WPT) technology based on simulation results and integrating and fabricating them with one IMD module. The small size receiving antenna has been designed for highly efficient IMD at 13.56HMz to meet ISM band specifications and the amount of energy required was reduced by developing ultra-low-power stimulation pulse generator. Both were implemented by PCB and integrated with one IMD for ANS stimulation to apply to animal models. Ex-vivo and in-vivo experiments were conducted to measure the power transmission efficiency(PTE) of the proposed inductive power transfer(IPT). After connecting the cuff electrode to the sciatic nerve of the rat model, the neural stimulator was located in the subcutaneous position and the incision was sutured. As soon as the power supply was started wirelessly, the rat model's femoral quadrant was observed to tremble significantly in line with the pulse iteration cycle, and the comparison with the measured EMG signal confirmed that the tremor was caused by the designed stimulus pulse. Finally, we confirmed that 7mm x 7mm x 3mm size IMD using a highly efficient ultra-small IPT system can sufficiently stimulate PNS, which can be extended to various ANS in the future. Neuromodulation of each nervous system may also contribute to the treatment of various diseases.