Physico-mechanical design of conducting polymers for neural interface applications [thesis]

Sungchul Baek
A key limitation associated with conducting polymers (CP) for implantable electrode applications is their inferior physico-mechanical properties and the effect of this on biological performance. This research investigates the physico-mechanical cues of conventional conducting polymer coatings and aims to understand their effects on neural adhesion and neurite extension. The underlying hypothesis was that the biological performance of CPs can be effectively controlled by physical cues such as
more » ... face topography and mechanical softness. Poly(3,4-ethylenedioxythiophene) (PEDOT) doped with perchlorate, benzenesulfonate, tosylate (pTS), dodecylbenzenesulfonate and polystyrenesulfonate were compared across a range of baseline material properties. Additionally, the deposition charge used to produce PEDOT was varied from 0.05 to 1 C/cm2 to determine an optimal thickness for electrode coatings. To address the need for electroactive biomaterials with improved neural interfacing, nanobrush-CP hybrids were fabricated. Dense poly(2-hydroxyethyl methacrylate) (PHEMA) brushes were grafted via surface-initiated atom transfer radical polymerisation (SI-ATRP). PEDOT/pTS was electrochemically deposited through this nanobrush substrate. The formation of the hybrid was confirmed and characterised across implant performance metrics. The physical, mechanical, electrical and biological performance of PEDOT coatings was used to assess ideal fabrication parameters, optimised for neural cell interactions. Nanoindentation techniques were used to yield the first quantitative values for stiffness moduli of electrodeposited CP coatings on metal substrates. It was found that the nodularity of the CP surface increased with increasing coating thickness and decreasing dopant size. A major finding of this study was that high roughness of conventionally doped PEDOT produced on the micron scale, prevented attachment of neural cells. Consequently, thin PEDOT films doped with the low toxicity anion, pTS, supported the greatest cell attachment and neuri [...]
doi:10.26190/unsworks/15921 fatcat:nojop7mx3zdmzpqfpkk6pli52m