Aerodynamically assisted jetting (AAJ) and threading

The jet phenomenon referred to as aerodynamically assisted jetting (AAJ) takes place within a pressurised chamber having within it a needle(s) accommodating the controlled flow of media (Figure 1). The developed pressure gradient derives from the input of controlled pressure to a sealed chamber, which at the top end has the needle or needles, which holds the flow of media (single or multi-phase) with the exit orifice (on the base plate) placed centrally and in-line with the needle exit(s). The input of a controlled pressure develops within the chamber, giving rise to a pressure gradient across the exit orifice (which is on the base plate) and generates an aerodynamic flow field. This developed flow field provides the driving mechanism for drawing out media emerging from the needle(s) through the exit orifice. Subsequently a liquid cone is formed at the exit of the needle(s) with the formation of a jet, which could be controlled to undergo instabilities at different lengths from the exit orifice, giving rise to the generation of droplets. Aerodynamically assisted jetting shares a unique feat with electrosprays, that is the ability to switch with ease from the generation of droplet to threads with the rather simple modulation of the media’s rheological properties in particular viscosity and viscoelasticity, which provide the elongational element for generating continuous threads from which scaffolds to membranes are conceived. AAJ much like electrosprays have the ability to handle high viscosity suspensions which could contain a wide range of materials from which fine micro to nanoscales structures are generated. Figure 2 demonstrate a multi-needle system. In addition to the aerodynamically assisted approaches we have alternative methods which do not require a pressurised chamber and is referred to as pressure assisted jetting and threading. All these approaches have been explored for directly handling advanced structural, functional and biological (from immortalised and primary cells to those stem cell cultures) materials. The living cells directly handled by these approaches have been shown to have a similar viability as BES and have been assessed from a molecular level upwards.