Study of Pinch-Off Locations during Drop-on-Demand Inkjet Printing of Viscoelastic Alginate Solutions.

The ligament pinch-off process of viscoelastic fluids during jetting is a key step in various biotechnology and dropwise three-dimensional printing applications. Various pinch-off locations have been investigated as a function of material properties and operating conditions during the drop-on-demand (DOD) inkjet printing of viscoelastic alginate solutions. Four breakup types are identified on the basis of the location of the first pinch-off position: front pinching is mainly governed by a balance of inertial and capillary effects, exit pinching is affected by the external actuation-induced hydrodynamic instability and mainly governed by a balance of elastic and capillary effects, middle pinching usually occurs any place along a uniform thin ligament under dominant viscous and elastic effects, and hybrid pinching happens when front pinching and exit pinching occur simultaneously as a special case.