BUCHI Encapsulator B-395 Pro - Manual (Page 56)

6 Operation
56 B-395 Pro Operation Manual, Version C
6 .9 .3 Working with the pressure bottle
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 slight vortex is visible. 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 the pressure bottle with the above described 1.5 % alginate solution and screw on the
assembled cap. Pass the silicon tube (4×7 mm) between the blades of the liquid flow regulating
valve and attach the male luer lock fitting of the silicon tube to the female Luer lock fitting of the
bead producing unit. Squeeze the valve by turning the knob clock wise so that the silicon tube is
closed.
3. Open the external pressurized air supply. The air inlet pressure is optimally at 1.5 to 2 bar (20 to 30
psi). However the system tolerates air inlet pressures of up to 7 bar (100 psi).
4. Set the air pressure to 0.4 bar at the pressure regulation system. Check the readout periodically to
verify that the air pressure still corresponds to the set value. Activate the vibration control system
and set the vibration frequency at 1100 Hz for the 200 µm nozzle and at 800 Hz for the 300 µm
nozzle.
5. Open the flow regulating valve by turning the knob counter-clock wise until the liquid flows through
the silicone tubing and the bead producing unit to the nozzle where it forms a continuous liquid jet.
Adjust the liquid flow and/or the frequency to obtain a good bead chain in the light of the strobo-
scope lamp. The desired setting is when the beads within the bead chain are clearly separated for
several centimetres, starting 3 to 5 mm below the nozzle. Record the position of the flow regu-
lating valve for this desired setting.
6. Increase the vibration frequency until the bead chain becomes unstable. Then increase the liquid
flow rate by slowly increasing the air pressure or by slowly opening the flow regulating valve until
a uniform bead chain is restored. Repeat this in the opposite direction by decreasing the flow rate
and compensating by decreasing the vibration frequency. This may be done until you become
familiar with the relationship between these two settings. Record the values in table 6-5.
NOTE
An air pressure setting from 0.1 to 0.8 bar is generally sufficient to pump the polymer mixture.
Working pressures greater than 1.0 bar should be avoided and are indicative of problems such as:
• Clogged nozzle,
• Overly viscous polymer mixture,
• Under sized nozzle for the polymer mixture in use.
7. 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 (approx. 2”) below the electrode.