Developing pressure sensors from impregnated textile sandwiched in inkjet-printed electrodes

This work presents an interesting fabrication route toward development of pressure sensing patch by utilizing electrically conductive cotton fabric sandwiched between two parallel electrodes. An all-printing strategy is adopted to simplify the manufacturing and minimize the overall cost. A conductive nanocomposite solution is developed by mixing carbon-based paste and an organic conductor PEDOT-PSS (poly(3,4-ethylenedioxythiophene). Several mixing ratios were investigated to analyze the optimal coating parameters and resulting percolation thresholds. A nanofibrous and stretchable cotton fabric is selected for impregnation with the nanocomposite solution, which is used as the pressure sensing layer. The metallic plates and interconnect lines are developed by inkjet printing Ag nanoparticles-based solution on a PET (polyethylene terephthalate) substrate. The thermally sensitive resin on one side of PET substrate enables sandwiching the impregnated fabric through lamination. A 3 × 3 sensing array is developed with each sensing cell having 5 × 5 mm² effective area. The piezoresistance is determined by exploiting the change in bulk resistance of the electrically conducting fabric caused by the physical deformations at microscale in the conductive threads partly due to percolation mechanism. The produced sensors are tested and are able to record resistance variation for as small as 1 gm weight. The results show that this type of sensors can successfully be applied for a wide variety of pressure mapping and force monitoring system requiring deployment on large areas.