This article explains how available volume is calculated in FluentControl™, and which parameters we should change to reduce the dead volume.
Occasionally, during liquid level detection you will be prompted with “User Prompt” “Not enough liquid detected” with three volumes indicated in the prompt “Available volume”, “Needed volume” and “Detected volume” (Figure 1.).
Figure 1. User Prompt when not enough liquid is available for the aspiration.
“Needed volume” is volume that is defined in the “Aspirate” command, and it is given to that command during the runtime either via variable or fixed value.
“Detected volume” is calculated by FluentControl based on the geometries of the wells given in the “Labware definition” (Figure 2.). These geometries are compared with the position of the FCA arm in the Z-axis when the liquid detection signal is received. The FCA arm position is known by the Z motor driver as soon as a detection signal is received from the cLLD board.
Figure 2. Compartment Definition in “Labware definition” shows the dimensions defined for each well of the labware.
Once aspiration begins, it is important that the geometries are defined correctly as during the “Aspiration” step FCA can move faster or slower than the liquid and cause overspill or air aspiration.
“Available volume” is calculated by FluentControl based on the geometries of the wells, position of the FCA arm in the detection moment and Z-max defined in the “Positions/Teaching” of the “Labware definition” (Figure 3.).
Figure 3. Z-Coordinates in the “Positions/Teaching” tab important for the calculation of the “Available volume”.
Z-max is the lowest point in the labware where FCA arm can reach to aspirate liquid. If this position is defined too high, then the volume available to be aspirated will be too small. Typically, Z-max is defined as 0.5 mm from the bottom of the well. In applications like NGS, Z-max could be even lower.
Considering everything mentioned above it is evident that the “Dead volume” represents the difference between the “Detected” and “Available volume” and it is often direct consequence of incorrect geometries or Z-max being defined too high. Every labware will have some dead volume but with correct labware definition and teaching it can be minimized.
For troubleshooting of “Not enough liquid detected” please check our article “Troubleshooting for ‘’No Liquid Detected” or “Not Enough Liquid Detected”.
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