Novel Crease and Wash-Resistant Electrically Conductive Inks for SMART Textile Applications

Due to the worldwide aging population, methods have been sought to improve the
efficiency of health care services. It is envisaged that remote monitoring of patients would
form part of the solution. Monitoring of patients would be via the use of functionalised
undergarments with the required technology embedded within. There have been
significant advances in flexible electronics but metal wires are still required for electrical
interconnects which compromise the comfort that the garment offers when in contact with
skin. Electrically conductive polymers are considered as viable replacements for these
metal wires. Electrically conductive polymers can have high electrical conductivities but
they can be brittle due to their inherent stiffness.
From studies reported in this thesis, various routes to the synthesis of PEDOT,
which would lend itself to function in crease and wash resistant conductive inks, were
investigated. The task was highly challenging due to the confliction between high
conductivity and structural rigidity of typical conductive molecules. A series of monomers,
described within, were designed, synthesised and characterised. These monomers provide
a foundation for further syntheses to the subsequent novel electrically conductive
polymers. In order to assess potential challenges in the formulation of crease and wash
resistant conductive inks based on conductive polymers, systems containing PEDOT:PSS
were designed, prepared and characterised. It was found that the use of just PEDOT:PSS as
the coating for cotton fabric provided an electrically conductive coating which was
susceptible to degradation during creasing and washing. To overcome this challenge, a
composite of a synthesised latex and PEDOT:PSS was devised which provided an electrically
conductive coated cotton fabric with an electrically insulating surface. The electrical
resistance could still be measured by incorporating electrodes prior to the application of
the final latex layer. Encouragingly, this composite provided a formulation having very low
electrical resistances pre- and post-wash.