Synthetic Neural Interface
Authors:Samuel Beach, Jason Farkas
Mentor:Luke Theogarajan, Associate Professor of Electrical and Computer Engineering Dept., Ventura Community College
We have established that a neural cell can be stimulated by a small increase in the background concentration of potassium ions in the extra-cellular fluid (an increase from 5mM to just 10mM is enough to cause sufficient cell stimulation). A 2-D array of artificial ion pumps, controlled by a light detecting sensor, could use this method of neural stimulation to restore vision in those with neurodegeneration of the retina. The current focus of this project is design and material selection for the ion pump. During this phase a planar proof of concept ion pump was used for testing.
We tested seven types of conjugated polymers (PEDOT:PSS, PANI, TCNQHE + Polyurethane, PEDOT:PSS with Silquest 187A, PANI / PEDOT co-polymer, and PANI plated on PEDOT). Each of these polymers were subject to the following tests; cyclic voltammetry using a potentiostat, submersion in salt solutions, and resistance inspection with an ohmmeter. These tests examined the polymers for electrical conductivity, membrane stability, potassium ion permeability, and the reversibility of their reduction/oxidation reaction. The chosen polymer was then incorporated into the proof of concept pump and the pump was tested for ion transport by cyclic voltammetry. The current through the pump when reservoirs were loaded with an ionic solution (1M of KCl, NaCl, or CaCl2) was compared to the current through the pump when the reservoirs were loaded with de-ionized water.
Our findings are that the only polymer that possesses the desired properties is the PEDOT:PSS with Silquest 187A. The current through the pump was 1 to 2 orders of magnitude greater when the reservoirs were loaded with ionic solutions versus de-ionized water, which indicates ion transport. The next phase of the project is to produce a stacked version of the ion pump with potassium ion selectivity.