Electrochemically deposited conducting polymers for reliable biomedical interfacing materials: formulation, mechanical characterization, and failure analysis
| Author(s) | Qu, Jing | |
| Date Accessioned | 2017-04-26T11:15:35Z | |
| Date Available | 2017-04-26T11:15:35Z | |
| Publication Date | 2017 | |
| Abstract | Conjugated polymers such as poly(3,4-ethylenedioxythiophene) (PEDOT) are of interest for a variety of applications including interfaces between electronic biomedical devices and living tissue. These polymers provide an improved interface compared to metal and semiconducting electrodes because of their ionic conductivity, relatively lower stiffness, and ability to incorporate biological molecules. Even though the signal transfer and biocompatibility of conjugated polymers are superior as the biointerfacing materials, the durability has been the weakest part for the long-term applications. Some efforts have been made to improve the durability of conjugated polymers, however, little quantitative information of the improved cohesion, adhesion and durability has been reported. ☐ In this thesis, the methods of improving the durability of conjugated polymer films, especially PEDOT, were investigated, including alternating the processing methods and components in synthesis. The 7-month in vivo testing showed a superior neural signal recording performance, however the durability of PEDOT films still needed to be improved. ☐ As a coating for biosignal transfer, the cohesion, adhesion and electrochemical stability of PEDOT are vital to determine the long-term performance. By far, not much information of cohesion and adhesion of conjugated polymer coatings has been dug out. In this thesis, a thin film cracking method was developed to measure the stiffness, strength and the interfacial shear strength (adhesion) of electrochemically deposited PEDOT. The estimated Young’s modulus of the PEDOT films was 2.6 ± 1.4 GPa, and the strain to failure was around 2%. The tensile strength was measured to be 56 ± 27 MPa. The effectiveness of crosslinker and adhesion promoter was demonstrated by this method. It was shown that 5 mole% addition of a tri-functional EDOT crosslinker increased the tensile strength of the films to 283 ± 67 MPa, while the strain to failure remained about the same (2%). With the modification of EDOTacid to the surface of stainless steel substrate, the interfacial shear strength was improved from 11.8 MPa to 32.5 MPa. ☐ To correlate the adhesion with the durability of PEDOT coatings, a tribology test was introduced. It was found that the durability of PEDOT on Au electrode was exceptionally good, and even better than the adhesion promoted coatings with EDOTacid on stainless steel and ITO substrates. The characterization method developed in this thesis made a critical difference in systematically comparing different materials, and provided valuable information for materials development and selection. | en_US |
| Advisor | Martin, David | |
| Degree | Ph.D. | |
| Department | University of Delaware, Department of Materials Science and Engineering | |
| Unique Identifier | 984148295 | |
| URL | http://udspace.udel.edu/handle/19716/21258 | |
| Publisher | University of Delaware | en_US |
| URI | https://search.proquest.com/docview/1884708017?accountid=10457 | |
| Title | Electrochemically deposited conducting polymers for reliable biomedical interfacing materials: formulation, mechanical characterization, and failure analysis | en_US |
| Type | Thesis | en_US |