Fabrication and electrical characterization of multi-layer capacitive touch sensors on flexible substrates by additive e-jet printing

Current consumer electronics, in particular touch displays and flexible electronics, were limited by the properties of existing commercial transparent conductor materials used as electrodes both in flat panel display and capacitive touch sensors. In this paper, an alternative fabrication technique using silver nanoink that can be used for rapid prototyping of high-resolution electrode arrays to replace indium tin oxide (ITO) for flexible electronics was presented. By direct printing silver nanoparticles on flexible substrates, capacitive touch sensors were fabricated onto polyethylene terephthalate (PET) film. Experiments were conducted to study the feasibility of electrohydrodynamic inkjet printing (e-jet printing) of high-resolution electrodes for touch sensors. Sensitivity of sub-20 μm capacitance sensor array was investigated in the study for droplet and humidity detection applications. The rapid prototyping method makes a significant impact in enabling simultaneously (1) customized and flexible touch sensors, (2) cost-effective manufacturing, and (3) high resolution and good sensitivity. The presented techniques can be used for the on-demand fabrication of customized conductive patterns for flexible and wearable electronics.