Droplet-on-demand printing of polymer solutions

Abstract

Droplet-on-demand inkjet printing of polymer solutions offers the possibility to deposit in a patterned way very small amounts of polymer functional materials. One of the characteristics of jetting on demand polymer solutions is the existence of a long stretching fluid filament between the main droplet and the fluid contained in the nozzle. The forces generated in the stretching fluid filament may be so large that initially the droplet leaves the nozzle but is retracted in course of its flight. The very existence of the fluid filament is a sign of the viscoelastic nature of the ink used. By investigating carefully the kinematics and dynamics involved in the stretching of the fluid filament, the rheology of the ink can be retrieved, especially its elongational properties. The kinematics involves the stretching of the fluid filament, the growth of the droplet during flight and tail hooking. The dynamics involve the deceleration of the main droplet, viscous forces and surface tension.