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4.8.2.5 Delay Mode (Cooling)
In TIME mode, especially when using larger and or thicker walled glass, active cooling may
not be sufficient to produce short pipette tapers. This may even be true at increased
PRESSURE settings (i.e., >500). In this case, it is recommended that the Delay mode of
active cooling be used. The method for changing to the Delay mode is described under
“Software Control Functions” and a brief description of the two modes of cooling is given in
“Programs”.
After switching to DELAY mode, one then has direct control over the delay between turning
the heating filament off and initiating of the hard pull. Because the cooling air is turned on
when the filament is turned off, increasing DELAY profoundly increases glass cooling before
and during the hard pull.
With a range of control over the degree of pipette cooling one can control the rapidity of
pipette taper. Higher DELAY values (longer delay) increase cooling and form a pipette with a
more rapid taper (shorter shank) while lower DELAY values (shorter delay) decrease cooling
and form a pipette with a more gradual taper (longer shank). Fortunately, cooling induced
changes in pipette taper generally occur with little effect on tip size. This is quite valuable as
the resistance of pipettes is a strong function of the length of the taper. By making a pipette
with a sharper taper, one can often decrease pipette resistance significantly without changing
the size of the pipette tip. Furthermore, the ability to control tip length is invaluable for
experiments where long tips are necessary for penetration into deep tissues or where short
stiff tips are necessary for adequate beveling.
Minimum and maximum useable values of DELAY can be expected; their exact values are
dependent on glass thickness and diameter. If DELAY is too short, the glass will not cool
sufficiently to form a tip and a long wispy fiber of glass will be formed. Values under 40 units
tend to be ineffective. At some maximal value of DELAY, the glass may be cooled too much to
separate during the hard pull. Under these conditions, the puller will typically execute
multiple cycles in order to separate the glass and the glass may break at a large tip diameter.
Maximum usable values of DELAY will be dependent on glass dimensions but are expected to
be near 200 units (200 ms) of delay.
4.8.2.6 PRESSURE Adjustment
The pressure setting controls the pressure of the cooling air delivered to the filament. The
higher the pressure, the shorter the pipette taper will be. Because thin walled glass cools
more rapidly than thick walled glass, the recommended values are ≤ 300 for thin walled
tubing and 500 for thick walled or standard walled tubing. By varying PRESSURE around
these values, the user can control pipette tip length over a moderate range.
4.8.2.7 Filament Width
Further control over pipette tip length can be accomplished by varying filament width.
Longer tips can be formed by using wider filaments and conversely shorter tips can be
formed by using narrower filaments.
4.8.3 Patch Pipette Fabrication
Micropipettes used for the electrophysiological recording technique of “patch clamping” are
generally characterized by short, stubby shanks and relatively large diameter tips (> 0.7
P-1000 FLAMING/BROWN MICROPIPETTE PULLER SYSTEM OPERATION MANUAL – REV. 3.02 (20161118)
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