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programming process. Unless otherwise stated, parameter adjustments assume that the
puller is in the TIME mode of active cooling (see Software Control Functions).
3.5.2
Micropipette/Microinjection Needle Fabrication
Consider the following programs using a 2.5 mm-box filament:
Sharp Microelectrode Program using 1.0 x 0.5 mm borosilicate glass
HEAT PULL
VELOCITY
TIME
PRESSURE
Ramp
150 75 250 500
Microinjection Pipette Program using 1.0 x 0.78 mm borosilicate glass
HEAT PULL
VELOCITY
DELAY
PRESSURE
Ramp 60 80 90 200
3.5.2.1
HEAT
The HEAT setting will affect the length and tip size of the pipette. Generally, higher HEAT
settings tend to give longer and finer tips. For trough filaments, the recommended starting
HEAT value is the ramp test value plus 15 units. For box filaments, the recommended
starting HEAT value is the ramp test value. The program listed above will typically have
heat on for 5 to 8 seconds after the <PULL> key is pressed. If the time is longer than eight
seconds and you are trying to pull a fine micropipette, increase the HEAT in 5 unit
increments until the pull takes place in less than eight seconds. If the pull occurs in less than
three seconds, decrease the HEAT until the pull takes place in 4 to 8 seconds. For the best
micropipette reproducibility with the finest tips, you should select a HEAT value that melts
the glass in 5 to 6 seconds. For microinjection pipettes, select a HEAT value that melts the
glass in about 7 seconds or longer.
3.5.2.2
PULL Strength
Low values of PULL strength in the range of 50 to 75 will give larger tips appropriate for
injection needles, while 80 to 150 give smaller tips appropriate for sharp microelectrodes. The
PULL strength can be set to any value desired with no danger of damaging the instrument.
3.5.2.3
VELOCITY (Trip Point)
The VELOCITY value determines the point at which the heat is turned off. VELOCITY
reflects the speed at which the two puller bars are moving during the weak pull. The lower
the VELOCITY value, the slower the speed of the bars when the trip point occurs. Although
VELOCITY can safely be set to any value from 1-255, all values over a maximal trip point
(usually about 150) will produce equivalent results. As the pull progresses, the speed of the
puller bars, as measured by the velocity transducer, reaches a point where further increases
in the VELOCITY trip point will not change the time point at which the heat is turned off.
VELOCITY is typically set between 80 to 90 for microelectrodes or 50 to 80 for microinjection
pipettes.
In a multiple cycle program, it is possible for the glass to separate before the trip velocity is
attained. Thus, the glass is subjected to heating as it separates. Such an occurrence can lead
to difficulties in forming tips as well as lack of reproducibility. If you are using a one-line,
looping program, try decreasing the VELOCITY a few units at a time. If your program is a
P-97 FLAMING/BROWN MICROPIPETTE PULLER OPERATION MANUAL – REV. 2.43 - DOM (20161118)
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