Author

Bo Weng

Year

2011

Degree Name

Doctor of Philosophy

Department

Department of Chemistry

Abstract

The main goals of this work are to 1) synthesize and optimize inkjet printable polypyrrole (PPy) nanodispersions, 2) fabricate PPy films and microstructures on a range of substrates under various printing conditions by using nanodispersions developed in 1), and 3) ultimately apply these printed structures in various fields, including controlled drug release, biosensors and tissue engineering.

PPy was chemically synthesised using different surfactants that also acted as dopants, and polyvinylalcohol (PVA) as a steric stabiliser. The effects of employing different surfactants and oxidants on particle distribution in the product, surface tension and conductivity were studied. Consequently, the polymerization conditions were optimized and an inkjet printable PPy nanoformulation that would resulted in solide stuructures with reasonable conductivity (~1S/cm) was obtained and printed successfully using a Dimatix Materials Printer 2800 (DMP2800) with low cost, userfillable piezo-based jetting cartridges.

PPy films and micropatterns were inkjet printed onto multiple substrates, including glass slides, ITO-coated glass and PVDF membranes. The morphologies, physical properties, electrochemical properties and thermal properties of the resultant films were characterized by profilometery, SEM, AFM, UV-vis, and cyclic voltammetry. In addition, cytocompatibility of these printed structures was demonstrated using PC12 cells.

An investigation into the use of printed micropatterned PPy scaffolds in tissue engineering was carried out based on the studies 1) and 2). A novel complex electroactive PPy/collagen scaffold was inkjet printed onto AryliteTM film for cell patterning and stimulation. 100 μm wide PPy tracks, approximately 1.4 μm high, with conductivity of 1.1 S/cm were obtained. Collagen was subsequently deposited directly on to the PPy surface. In vitro cell studies using a PC12 cell line verified that this scaffold effectively guided and patterned PC 12 cells - more than 90% of the cells adhered to the PPy/collagen tracks. Electrical stimulation was shown to promote neurite outgrowth and orientation. Inkjet printing is a convenient route to producing patterned conducting polymer structures that can promote cellular adhesion and provide a platform for electrical stimulation.

In addition, inkjet printed PPy/enzyme biosensors were also studied. PPy/enzyme formulations were printed onto the screen printed carbon electrodes and used as biosensors for hydrogen peroxide. A continuous and stable response was obtained in a broad concentration range upon the addition of hydrogen peroxide/glucose. All printed biosensors were fabricated successfully by inkjet printing.

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