BUCHI Encapsulator B-395 Pro - Manual (Page 57)

6 Operation
57 B-395 Pro Operation Manual, Version C
NOTE
The stronger the circular dispersal of the bead stream the better is the bead homogeneity. This does
not only depend on the electrostatic tension, but the liquid flow rate and the vibration frequency are
also factors. Ideally, the bead should separate from the liquid jet within the electrostatic field between
the nozzle and the end of the electrode.
8. As soon as a symmetrical and stable dispersal is obtained, remove the plate from the beaker
filled with polymerization solution or replace the beaker of water with the beaker of polymerization
solution and the stir plate (and the grounding forceps), and collect the beads for about 1 minute.
Record the process parameters in table 6-5 while the beads are accumulating. Cover or switch
the beaker and stop the bead production by turning off the electrostatic voltage, air pressure
control and vibration control.
NOTE
Clean the nozzle thoroughly immediately after each run with distilled water to avoid nozzle clogging or
partial occlusion due to dried out polymer mixture.
9. Check the beads under a microscope with a micrometer scale eyepiece, and record your obser-
vations of diameter, uniformity and shape in table 6-6.
10. Repeat this process for each change in process parameters.
Table 6-6: Encapsulator trial test work sheet (pressure bottle)
Nozzle size [ µm]
Alginate concentr. [%]
Position of the flow regulating valve
Vibration frequency [Hz]
Amplitude
Approximate bead size [ µm]
Homogeneity [%]
Comments
NOTE
When producing small beads with a diameter <500 µm, it may occur that their shape is not spherical
but somewhat oval. This is mainly due to the surface tension of the polymerization solution. A very
critical point for the bead is it‘s entrance into the polymerization solution. If the surface tension is
high, then the bead is partially held back at the surface and polymerization starts before the bead can
regain a round shape. This problem can be eliminated by adding a small quantity of surfactant like
Tween 20 to the polymerization mixture.
11. Compare the influence of the electrostatic tension by collecting beads at the same vibration
frequency and pumping rate with and without the electrostatic tension function turned on.