Description
Spinal cord injury affects between 243,000 and 347,000 people in the U.S. As a treatment, there are several methods being developed to stimulate neurons in the spinal cord after injury. The objective is to restore functionality to those individuals with damaged nerves. One approach involves electrical stimulation by using neural probes with microelectrodes. However, researchers have been using an external reference electrode which can cause areas of potential infection. In this work, we demonstrate a silver/silver chloride quasi-reference electrode with a new probe design to improve functionality. To fabricate it, silver was deposited, and silver chloride was grown on top with a ferric chloride solution. This type of quasi-reference electrode was chosen due to certain advantages such as: its simple construction, the inexpensive manufacturing, its stable potential and its nontoxic components. To simulate in-vitro the manner in which the devices would work in the body, we immersed them in Phosphate Buffered Solution that mimics body fluids. Afterwards, we tested the devices with several methods. First of all, Fourier-Transform Spectroscopy was used to acquire the spectrum of the quasi-reference electrodes. Second of all, Scanning Electron Microscopy was used to characterize the layer of silver chloride. Energy-Dispersive X-Ray Analysis allowed us to obtain quantifiable data of the surface of the quasi-reference electrode. Cyclic Voltammetry was used to obtain the charge storage capacity of the working electrodes and finally, Electromechanical Impedance Spectroscopy measured the impedance of the glassy carbon electrodes across a frequency range. Results from FTIR confirmed that silver-chloride had indeed grown on top of the silver layer. With EDX we observed that the silver sample had no chloride on it and, when analyzing different samples that had been submerged in FeCl3 we obtained between 2.58 and 10.22 weight % of chloride. With cyclic voltammetry we can also conclude that the behavior of both reference electrodes is the same and there is only a small shift of the quasi-reference electrode when compared to the original reference electrode. In addition, we compare the impedance values from EIS when using these two reference electrodes and we can conclude that they are very similar.
