BUCHI Encapsulator B-395 Pro - Manual (Page 53)

6 Operation
53 B-395 Pro Operation Manual, Version C
6 .9 .2 Working with the syringe pump
1. Attach a 200 µm or 300 µm nozzle to the bead producing unit. Place the assembled cover
plate on the control unit. Attach it with the two thumb screws. Put the vibration unit on the bead
producing unit. Connect the electrode with the red wire to the electrostatic dispersion unit (EDU).
Put the magnetic stirrer below the nozzle and a large beaker on the stirrer. Fill the beaker with
100 mM CaCl
2
so that at least 2 cm (approx. ¾”) is filled with the polymerization liquid. Put a
magnetic stir bar in the beaker and adjust the stirrer, so that a slight vortex is visible. A vortex in
the liquid will create shear forces which may deform the beads. It is best to use a stir bar without
a spin ring (supplied) because the spin ring will raise up the stir bar and may crush the beads
beneath it. Also, place the grounded clip over the edge of the beaker and into the liquid. At this
time, either cover the beaker with a plate (petri dish) or move it and the stirrer out of the way and
position another beaker with water in it (and the grounding clip) under the nozzle in its place.
2. Fill a 60 mL syringe with the above 1.5 % alginate solution and install it on the Encapsulator.
3. Activate the vibration control system and set the vibration frequency at 1200 Hz for the 200 µm
nozzle or at 900 Hz for the 300 µm nozzle. Activate the syringe pump and set the pumping speed
to 5 mL/min for the 200 µm nozzle or 8 mL/min for the 300 µm nozzle. Depress the “turbo” button
until a continuous liquid jet is formed. Release the “turbo” button and the jet will soon stabilize at
the preset flow rate. Adjust the pumping speed and/or the frequency to obtain a clear bead chain
below the electrode.
4. Activate the electrostatic dispersion unit at 500 V. Increase the voltage by steps of 100 V to get a
circular dispersal of the bead stream 3 to 10 cm (1” to 4”) after the electrode. An optimal distance
is about 5 cm (approximately 2”) below the electrode. If nothing happens, verify that the electrode
is connected to the control unit.
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 he liquid flow rate and the vibration frequency are
also factors. They influence the way that the bead is separated from the liquid jet within the electro-
static field between the nozzle and the end of the electrode. Smaller beads are often separated from
the liquid jet nearer to the nozzle than larger beads.
5. As soon as a symmetrical and stable dispersal pattern is obtained, exchange the beaker with
the beaker containing polymerization solution. Collect the beads for about 1 minute. Record the
process parameters in table 6-4 while the beads are accumulating. Cover the beaker (or exchange
it with the previous beaker containing waste) and stop the bead production by turning off the
syringe pump, vibration control and electrostatic voltage.
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.