Towards Advanced Bionics: Plasma Immersion Ion Implantation of Conductive Polypyrrole Films

Abstract

This thesis investigates the use of Plasma Immersion Ion Implantation (PIII) to modify electroploymerised polypyrrole (PPy) to allow for surface covalent binding of a range of biomolecules for biofunctionalized bionic applications. Synthesis regimes were investigated, aiming to produce PPy samples with the highest degree of batch consistency, chemical homogeneity and electroactivity. Galvanostatic samples at 0.2mA proved to produce superior PPy samples. PIII of nitrogen ions into PPy was modelled using TRIM/SRIM software. The depth of the treated volume of PPy was determined, along with the understanding of the atomic cascade into the PPy substrates. The modelling suggests that PIII of PPy will create an inhomogeneous treated volume with a composition that varies with depth. Surface carbonisation will occur as hydrogen atoms are recoiled or displaced. Changes in the composition and structure of PPy was investigated with a range of analytical techniques. PIII treatment of PPy was shown to produce a carbonised layer with increased carbon saturation. A threshold treatment time of between 40-80s is shown to exist, where any additional treatment beyond this amount has minimal impact on the composition and properties of PIII treated PPy. PIII treatment was shown to produce hydrophilic surfaces as a result of atomic reorganisation. A range of biological species were shown to be able to be covalently bound to PIII treated PPy. These include the ECM proteins tropoelastin and collagen I, the bioactive enzyme horseradish peroxidase, and the tropoelastin peptide fragment Pep36. Covalent binding was confirmed via use of SDS washing procedures. Conformation of the proteins and activity of the enzyme were shown to be maintained, as an outcome of the surface energy produced from treatment. The addition of ECM proteins to the treated surface were shown to increase the proliferation and binding of human dermal fibroblasts.