Page 377 - IJB-10-3

International Journal of Bioprinting Multi-physical field control inkjet bioprinting

Figure 5. Effect of the applied pulse width on the microdroplet diameter (A) and velocity (B). (C) Experiments show that the microdroplet diameter and
velocity increased at first and remained constant as the pulse width increased.

Da tb e= 3 + 3 ( t − 02/ .) + c 1 (VI) was approximately 1 m/s. Equation VI was calculated
by integrating the pressure and pulse width function
(Equation III) and fitting the test data (the formula
where D and t are the diameter and pulse width, derivation process shown in the Supplementary File). The
respectively, and a , b , and c are -28.1, -711.3, and 695.1, relationship between microdroplet velocity and the pulse
3
1
3
respectively. Analyzing the experimental results showed width, as defined by Equation VII, is:
that when a microdroplet was extruded, the pressure
remained positive for a short time, and the microdroplet V =− a e ( t − 02/ .) + b 4 (VII)
4
was not dispensed entirely. The negative pressure caused
the microdroplet to snap earlier, which reduced the
where V and t are velocities and pulse width,
microdroplet diameter. As shown in the chart, the positive respectively, and a and b are 3.27 and 1.12, respectively.
pressure time increased with the increase in pulse width, In Figure 5C, several special pulse widths were selected
4
4
increasing the microdroplet’s diameter. When the pulse to display the velocity and diameter of the microdroplets.
width increased to 0.8 ms, the positive pressure pushed The figure shows the variation of microdroplet velocity and
the microdroplets entirely away from the nozzle, and diameter with pulse width. These formulas for pulse width
thus the pulse width had little effect on the diameter of remain valid even if the printing material is altered. Only
the microdroplet.
the coefficients of the formulas need to be determined
Figures 5B shows that when the pulse width was 0.25 through experiments before using them. The reasons for
ms, the minimum speed was approximately 0.2 m/s. When the experimental results for microdroplet speed were
the pulse width reached 0.8 ms, the maximum velocity analyzed. When the pulse width was small, a large part

Volume 10 Issue 3 (2024) 369 doi: 10.36922/ijb.2120