Impact of textile substrates, conductive and dielectric inks on capacitive sensors for e-textiles

The development of sensors based on conductive and dielectric inks integrated on textiles requires the knowledge of the parameters that influence on printing process, as well as the characteristics that the textile provides to the sensor. Dielectric inks are usually used to obtain the capacitive sensor, but in this work, a textile has been used directly as the dielectric part. Thus, the same textiles influence sensitively on the value of the permittivity and the thickness of the dielectric of the capacitor, two fundamental parameters on the estimation of its capacity. On the other hand, the choice of the conductive ink, its viscosity features, solid content, as well as printing parameters, such as printing direction, also impacts on the way of obtaining the electrodes of the capacitive sensor, a less important parameter for the estimation of the capacity, but determinant to select the fabrics that can be printed. This work studies the influence of fabrics, inks and printing parameters to print a capacitor on a textile. The results will contribute to smart textile applications based on projected capacitive technologies. The experiments carried out on different fabrics and inks have provided results with capacities of less than 60 pF, the limit where the sensors based on capacitive technologies are located.