Page 69 - IJB-2-1

Hui Wang, Sanjairaj Vijayavenkataraman, Yang Wu, et al.

which is commonly referred to acetic acid was used as
the solvent. Polycaprolactone (PCL) pellets with an
average molecular weight of 80 kDa (Polycaprolac-
tone, Scientific Polymer Products Inc, Ontario, NY)
was used as the solute biomaterial. PCL pellets were
put in the acetic acid solution (50%, 60%, 70%, 80%
and 90%) (w/v) and sonicated by using an ultrasonic
sonicator at 30°C and 40 kHz for 3 hours. Then, the
mixture was stirred well and re-sonicated for another

1.5 hours in order to obtain a homogeneous solution. Figure 1. Conceptual diagram of E-jetting system.
The solution was left at room temperature for a while
before unloaded it into the syringe for E-jetting pur- IDE is the software that controls the movement of the
pose. Polished silicon wafers with the diameter of 100 XYZT stage through a communication interface,
mm were used as substrates. which also gives the real-time position and velocity
2.2 Experimental Setup information for effective monitoring and control.
The working principle is based on the balance be-
An E-jetting system was built in-house for the purpose tween the electrostatic force and the combined surface
of fabrication of scaffolds. The schematic diagram of tension and viscoelastic force of the liquid. A high
the experimental setup and the actual system are voltage (DC) is applied between the nozzle and the
shown in Figure 1 and Figure 2, respectively. The substrate, typically in the order of 2−3 kV. The sur-
main components of the system are namely, the high face tension force of the liquid at the nozzle tip was
voltage power source, a high precision XYZT stage overcome by the electrostatic force between the nozzle
along with the controller, a syringe pump and a and substrate, hence forcing the solution to come out
computer. The software for stage control, connecting of the nozzle and printed onto the substrate. The
tubes, syringes and needles are other components. A whole process happens in two stages. The first stage
13 mm internal diameter syringe and 0.5 mm internal was the formation of the Taylor cone at the apex of
diameter needle were used in all the experimental tri- the conical meniscus, due to which the electric field
als. The high precision stage, purchased from Aerotech stretches the liquid. Then it progresses to the second
Company (Pittsburgh, PA, USA) was driven by linear stage of Rayleigh-Plateau instability. As the electric
motors. The X and Y axis has the travel distance of up field force increases, Rayleigh-Plateau instability be-
to 150 mm and can be precisely controlled up to 3 comes larger than the combined surface tension and
μm, while the Z axis has the travel distance of 50 mm viscoelastic force, while a jet of liquid is formed and
and can be precisely controlled up to 5 μm. Ensemble ejected continuously onto the substrate. The substrate

Figure 2. In-house E-jetting system.
International Journal of Bioprinting (2016)–Volume 2, Issue 1 65