480450 Photopolymerizable Conducting Polymer-Hydrogel Composites
Electrically conductive hydrogels lend themselves to an array of biomedical applications, such as in vivo and in vitro bio sensing, neural stimulation, bioelectrical signal processing and controlled drug delivery. In this work, the fabrication and properties of poly(ethylene glycol) diacrylate (PEG-DA) as a scaffold matrix for the conductive polymer poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) was explored. The well-defined biocompatibility and electrical characteristics of PEDOT:PSS offer a way to impart conductivity and charge storage to PEG-DA hydrogels for biological implantation and instrumentation. On the other hand, the ability to photopolymerize the PEG-DA allows for the ability to microfabricate conducting polymer-hydrogel composites. Increases in electrical activity allow inert hydrogels to cross the threshold into interactive and controllable systems. Various characteristics of the PEGDA-PEDOT composites have been measured here. Compressive modulus, charge storage capacity and conductivity were determined by the use of dynamic mechanical analysis (DMA), cyclic voltammetry (CV) and four-point probe, respectively. Electrical and mechanical tests were performed on hydrogels with varying concentrations of the conducting polymer (from 0 to 15 wt%). Compressibility, charge storage capacity and conductivity ranges of 27.4 – 2709.9 KPa, 1.68 – 19.89 mC/cm2, 0.002-0.041 S/cm were determined respectively. Increasing PEDOT concentration was found to have an inverse relationship on the compressive modulus and path length of polymerization, while electrical characteristics dramatically improve with the addition of PEDOT. Finally, the viability of microstructure patterning was confirmed by UV photolithography techniques. The importance of these findings will enable hydrogels to be accurately tuned for conductive applications with defined mechanical stabilities by addition of PEDOT:PSS.
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