Biotek MicroFlo select, Operator'S Manual

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28 | Essential Concepts
BioTek Instruments, Inc.
How it works
The MicroFlo Select dispenses fluid using a peristaltic pump. It works by expelling a
portion of fluid trapped between advancing rollers. The shape of the tubing between
the rollers is similar to sausage links in a continuous strand.
The volume of fluid in a single sausage depends on the tubing size and linear distance
between rollers. As the rollers spin the fluid advances and is expelled at the tip in finite
aliquots (or sausages). The volume of each aliquot is the amount of fluid squeezed
between two adjacent rollers.
The stepper motor turns the pump a determined number of steps. The pump drum can
be advanced in smaller increments than the distance between rollers to expel a fraction
of the full aliquot. However, the volume of the fractions is variable, depending as it
does on many factors (exact rotor position, tubing tension, tip geometry, etc.). The
variation between volumes of fractional aliquots is significantly higher than between
dispenses done with full aliquots. Thus, the best possible performance and
reproducibility from dispense to dispense is done in full aliquot increments. That is, 1
µL dispenses when using the 1 µL cassette, 5 µL dispenses when using the 5 µL
cassette, and 10 µL dispenses when using the 10 µL cassette.
The tubing cassettes are calibrated by stretching the tubing to the size required to
accurately dispense the expected volume per aliquot. BioTek calibrates cassettes to
meet the MicroFlo’s specifications before shipping them. Over time the tubing’s
properties will alter slightly, but the cassettes can be recalibrated to restore expected
performance, in most cases.
Review the
Specifications on page 7 to learn the expected life of the tubing cassettes.
Rollers
1 aliquot