Optimisation of a novel direct-write dispenser printer technique for improving printed smart fabric device performance

Common fabrics such as cotton and polyester cotton have a rough and high porosity surface compared to typical printed electronics substrates such as FR4 and Kapton. This surface type adversely affects uniformity and performance of printed electronic layers. This paper reports for the first time, an optimisation process for a dispenser printable ink on 65% polyester 35% cotton blend woven fabric for printed smart fabric applications. In this work, the ink is an interface layer material, (Fabinks-IF-UV-1004) which is printed directly on the untreated fabric to provide a smooth homogenous platform allowing the printing of subsequent electronic ink layers. This work makes use of dispenser printing, a direct-write process where an electrically functional ink is directly deposited on the areas of substrate defined by a computer pattern. It is a novel state of the art process which has been developed for use in printed smart fabrics by the University of Southampton. It offers features of: custom digital patterning, the ability to print multi-layered and multi-material structures and is a rapid prototyping process. The optimised interface layer reduced the surface roughness of the fabric (characterised by surface roughness parameter Ra) by 74%. The optimisation of interface layer on the polyester cotton, detailed in this work, can be replicated on most types of fabrics.