I just read this article:
“University of Tokyo researchers have developed a new ink that can be printed on textiles in a single step to form highly conductive and stretchable connections. This new functional ink will enable electronic apparel such as sportswear and underwear incorporating sensing devices for measuring a range of biological indicators such as heart rate and muscle contraction.”
Conductive ink, especially when printed on a stretchable or flexible medium such as cloth fabric, is notorious for its inconsistencies in electrical properties, particularly resistivity, caused by environmental forces.
According to the research group, “We were able to achieve this by use of a [fluorine surfactant] that allowed the silver flakes to self-assemble at the surface of the printed pattern, ensuring high conductivity.” Interestingly, fluorine surfactant helps make fabrics water-resistant. Furthermore, fluorine surfactants play key economic roles for DuPont, 3M, and W. L. Gore & Associates.