Surfactants influence jetting dynamics and drop formation in inkjet printing

Surfactants are used in many product formulations, including pharmaceuticals, motor oils, and household cleaning products. In recent years, these versatile surface-active agents have found application in biotechnology, microelectronics, and viral research. Antonopoulou et al evaluated surfactant behavior in the distinctly different application of inkjet printing.

The timescale involved in drop-on-demand inkjet printing (usually less than a microsecond) presents issues with surfactant transport. Through numerical simulations and experimental observations, the authors demonstrated the effects of surfactants on jet breakup and drop formation during jetting.

“The flow and surface expansion rates associated with jetting are much higher than typical timescales of surface diffusion and surface adsorption of surfactants,” said co-author Evangelia Antonopoulou. “Consequently, surfactants are unevenly distributed with a higher concentration on the surface of the drop compared to the ligament.”

Study results show a stronger surfactant can prevent breakup of the main drop when using viscous fluids. Marangoni forces arising from surface tension gradients can delay and even prevent the formation of satellite drops.

The model developed in this investigation could translate to other rapid drop formation processes, such as those found in sprays.

“Here, we focused on a simple surfactant water system,” said Antonopoulou. “However, our model could in principle be extended to consider fluids with more complex surface rheology, including surface active polymers and biological fluids containing phospholipids or proteins, for which dynamic surface tension can be used as a diagnostic tool.”

Source: “Effect of surfactants on jet break-up in drop-on-demand inkjet printing,” by E. Antonopoulou, O. G. Harlen, M. Pump, T. Segers, and M. A. Walkley, Physics of Fluids (2021). The article can be accessed at https://doi.org/10.1063/5.0056803 .