Effect of the solvent evaporation rate of silver ink on the electrohydrodynamic-printing formability of textile-based printing electronics

The enabling electrohydrodynamic (EHD) printing technology in a one-step forming, continuous, and controllable manner has gained wide attention in the field of flexible printed electronics. The evaporation characteristic of ink solvent during the EHD printing greatly affects the shape of the jet as well as the penetration and diffusion of inks on fabrics, which is crucial to the formation of high-quality printed electronics. However, few works have deeply investigated the control of ink solvent evaporation to adjust the formability of EHD printing electronics on rough and porous textiles. Here, conductive inks with different solvent evaporation rates are formulated. The effect of solvent evaporation on the motion of inks is evaluated by the contact angle over time. Furthermore, the morphology and electrical properties under different deformation of EHD-printed conductive lines are observed and measured. The results show that the morphology of conductive lines printed on fabric could be accurately controlled by the ratios of the solvent in inks, and the solvent evaporation rate has a significant inverse-parabolic effect on electrical resistance and its stability under deformation. Moreover, the serviceability of the optimal ink is demonstrated by the performance of an EHD-printed antenna for ultra-high frequency radio frequency identification tags, and its maximum reading range is 9.1 m under typical application examples. These findings will provide a guide for ink formulation and process control of EHD printing in flexible textile-based electronics.