Research Of Artificial Facial Nerve Electrode

Objectives: Facial paralysis often causes the loss of tone, eye closure dysfunction, and facial expressions due to facial nerve injury. There are currently no effective treatments for long-term peripheral facial paralysis, so we proposed and investigated a new method where we established an artificial facial nerve reflex to restore the denervation of facial features. We used an electronic chip to replace the control center of the facial nerve. In the process of establishing the reflex arc, there are three key problems need to solve. First, what subject is the best choice of the electrode and how to modify it.Second, is the interaction problem between the electrode and the surrounding tissue. The third problem we must solve is that we must find out the relationship between the electrical characteristics of the orbicularis oculi muscle and mechanical contraction characteristics. The theory of relationship between them decides the number of electrodes we want implant into the orbicularis oculi muscle, and also determines the location and spacing of these electrodes implanted. It is the key in the entire nerve reflex arc, and also is the third theorial problem of this research to solve. In our study on implants, we employed 20-μm diameter platinum wire as the microelectrode material. However, this wire is very thin and has high electrical impedance, so we coated the wire with nano platinum black, which significantly decreased the electrical impedance. We study the interactive influence of implanted nano platinum black electrode on rabbit orbicularis oculi muscle morphology and function. The other part is to study the electrical stimulation characteristics of orbicularis oculi muscle and the characteristics of the mechanical contraction. As an animal model of implantation, sweep key obstacles of establishment in facial nerve reflex arc and lay a theoretical foundation.Methods: 1. Experimental animals: New Zealand white rabbit(permission number: SCXK(SH)2012-0007, SYXK(SH)2009-0086). 2. Human facial nerve electrode material- science research According to comparison of different electrodes feature, and the comparison of electrode manufacture craft, choose suitable electrode and process for artificial nerve system. 2. Comparative studies on implantation of nano platinum electrode and pure platinum electrode in rabbit orbicularis oculi muscle We monitored the interactive influence of two types of electrodes(flexible nano platinum black electrode and traditional pure platinum electrode) on the orbicularis oculi muscle of rabbit model of facial paralysis by administering biological electric current and exciting current to biological tissue and identifying morphological and functional changes. Long-term electrical stimulation affected the orbicularis oculi muscle contraction, and electrode configuration and performance changes were observed before and after implantation. 3.Electrical stimulation characteristics of denervated orbicularis oculi muscle We observed the stimulus current diffusion regularity and its relationship with mechanical contraction in the orbicularis oculi muscle using an electrode gathering line. 4. Statistical method a. Data analyses were performed using SPSS software version 18.0(SPSS Inc., Chicago, IL, USA) and the means were compared using paired t-tests at p<0.05. b. SPSS18.0 software was used for statistical processing. Data is presented as the mean ± standard deviation(SD). Between-groups comparison was made using a paired t-test(mean ± standard error,SE), with p < 0.05 indicating a statistically significant difference.Results: [1]. we employed 20-μm diameter platinum wire as the microelectrode material. This wire is very thin and has high electrical impedance.We therefore coated the wire with nano platinum black, which significantly decreases the electrical impedance. [2]. Nano platinum black electrode is superior to pure platinum electrode in the following aspects: morphology and functionality, electrical excitation function of the orbicularis oculi muscle as assessed by electromyography(EMG), muscle contraction function, and animal model biological tissue observation. And nano platinum black electrode features have good stability. [3]. a. Under different stimulus intensities of 2 or 4,5 m A, the closer the recording electrodes were to the stimulating electrode, the larger was the amplitude. When the recording electrode and stimulating electrode distance increased, the amplitude declined linearly with decreasing function. In addition, current conduction across the muscle fiber was studied. b. Under different stimulus intensities of 2 or 4,5 m A, it was found that the closer the recording electrodes were to the stimulating electrode, the larger was the amplitude. When the recording electrode and stimulating electrode distance increased, the amplitude declined linearly with decreasing function. c. The transverse current reached a maximum 4 m A range, and increasing the current intensity did not increase the propagation range. Longitudinal current, even in the range of 6 mm, can still record electrical activity. d. At the same distance, and palpebral fissure rate is related to the intensity of stimulus, palpebral fissure and stimulation intensity changes comply with linear equation.Conclusions: 1) A biocompatible polymer parylene film, made with a plasma-enhanced chemical vapour deposition system, was used to cover the electrode and platinum wire(0.02 mm in diameter), acting as a flexible insulator. 2) The microelectrode surface modification with nano platinum black can effectively increase the microelectrode surface area, improve electrode performance, and feature good tissue compatibility. 3) Under different stimulation intensities, the larger the stimulus intensity, the greater is the potential change and the faster is the attenuation. 4) Longitudinal current, even in the range of 6 mm, can still record electrical activity. While a transverse current diffuser has a maximum range of 4 mm, increasing the current intensity does not increase the propagation range. 5) According to conclusion 3 and 4, artificial facial nerve stimulation electrode should be placed according to the edge of the orbicularis oculi muscle(cross) nerve fibers within 4 mm and within 6 mm along(a nerve fiber). 6) At the same distance, and palpebral fissure rate is related to the intensity of stimulus.