LIMS & Lab Automation
Barcoded Tube Rack Readers for Automation Stephen Knight and Neil Benn, Ziath Ltd
There are several manufacturers of 2D-barcoded rack readers for SBS/SLAS format tube racks and virtually all of them claim that their unit can be integrated with a laboratory liquid-handling robot. So how easy it is in reality?
Why add a barcode reader to the automation platform?
This may seem obvious, but there are actually good reasons not to add the reader to the platform. Most robots are designed with a certain number of spaces on the ‘deck’, or operational area, in which defi ned functions can be carried out. Whilst it is true that the robot can be specifi ed with more or less deck positions, the initial cost of the instrument increases as more positions are added. If the throughput of a laboratory using barcoded tubes is relatively low, it may not be sensible to dedicate one area of the deck just to hold a barcode rack reader. Instead the stand-alone unit can be on the bench nearby or in the sample processing area.
When to add a reader?
As throughput increases, it makes more sense to integrate a barcode rack scanner directly with the robot. Firstly, it saves bench space and secondly it can help to eliminate errors between reading the rack at a remote location and positioning it on the robot deck. This is normally caused by switching the orientation of the rack during transfer, which sounds simple and obvious, but occurs more often than you might think! However, a linear, or 1 dimensional, barcode on one short edge of the rack can help to eliminate this issue, as the rack can then only be read in one, correct, orientation. Many barcode rack scanners can also be fi tted with a linear reader to facilitate this, but robots can also carry their own linear barcode readers.
Where to put the reader?
There are two options for integration with an automation platform, either on-deck or off-deck. Off-deck in this case would mean adjacent to either the left or right short side of the system and this can be the most convenient position, especially if the reader is rather high in construction. On-deck allows easier access by the gripper arm and dispense needles in most cases, but can, of course, take up more than one plate position with most reader designs. The exception is the Ziath Express (Figure 1) which has a footprint not much greater than an SBS plate/rack and therefore only uses one position on some automation platforms. Another consideration will be where to run the power, signal and control cables for the scanner. In some basic units, these may be combined into one cable, usually a USB, but this limits the amount of power available for illumination of the rack underside during reading.
How high can you go?
Reader height is a big consideration if an on-deck integration is required. Some manufacturers of camera-based readers use relatively tall housings in order to achieve the longer focal length necessary to read tubes of different base heights - that is the height of the tube base in the rack relative to the scanner glass. The apparent depth of fi eld and the point of sharpest focus are critical to successful reading. By using pin-hole cameras with a longer focal length, the depth of fi eld can be increased, but at the expense of a higher instrument. Ziath has solved this problem in the Datapaq Mirage design (Figure 2) by using a 45-degree mirror to maintain focal length while reducing the height of the instrument. In the Datapaq Express design from Ziath, four separate cameras are used to divide the rack image which is later re-combined in software. By imaging only part of the rack area with each camera, the focal length can be shorter than that of a full rack imager and the scanner height can again, be kept to a minimum. A similar strategy is employed in the Ziath Cube scanner (Figure 3) which uses two cameras to image the larger cryo-racks, in addition to the SBS format.
Figure 2: DataPaq Mirage reader.
Figure 1: Express linear reader with TraceTraq 0.75ml yellow push caps.
Figure 3: Cube scanner with red screw capped tubes in rack.
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