Barcodes can be especially useful and have numerous benefits, yet implementing them well can be challenging.
Implementing barcodes is a frequent topic for conversation when developing processes for automation. This seemingly benign topic can create havoc and can be a source of a multitude of issues when doing an automation project. Barcodes can be especially useful and have numerous benefits, yet implementing them well can be challenging. Anyone who has done a self checkout at the local grocery store will know that some barcodes are more easily read than others. Some require multiple attempts and sometimes they never decode. No doubt there are multiple reasons why this happens. Yet in a grocery store, troublesome barcodes can be rescanned with multiple pulls of the trigger or simply manipulated for a better angle on the scan. In lab automation systems, however, better reliability is required when decoding barcodes. Failure to scan or decode properly can cause significant headaches, and the barcodes can fail in numerous ways. The following article addresses many of the issues and failures that can occur when implementing barcodes in the lab.
Benefits for Using Barcodes in the Laboratory
|Reduce Manual Entry/ Reduce Errors||Barcodes and bar code scanning can be used to reduce if not eliminate manual data entry. An average person entering data will produce 1 error in 300 keystrokes. The worst-case for errors for a 1D code 128 barcode is 1 in 2.8M; a 2D data matrix barcode can produce 1 in 10.5 million.|
|Improve Productivity||Aid in streamlining and automating processes by eliminating manual intervention|
|Add Traceability||Barcodes are useful for tracking samples, inventory, and assay plates in the laboratory. If not implemented and maintained properly this issue can cause numerous headaches|
|Need for Accountability||Logging when a process was completed on a sample or assay plate or recording when someone did a required process task.|
|Improve Efficiency||In terms of large inventories, the use of barcodes and automation can greatly reduce labor costs.|
|Improve Accuracy (Accurately ID)||Less data entry and process errors.|
|Improve Customer & Employee Satisfaction||Another major constraint for automated system design is that laboratory square footage is expensive, and automation can take up a good deal of real estate. Having a laboratory with an open floor plan is the most ideal situation, but there are times when automation may have to literally fit in a closet.|
|Storage Requirements||When there is a new container that something will be held or stored for a period of time|
|Need for Identification||When you need to ID something (tips on a liquid handler)|
Types of barcodes
There are about 30 major barcode formats commonly used today. These can be grouped into three primary symbolic types.
- Numeric-only barcodes; These are one dimensional barcodes that encode only numbers. Some examples are UPC, code11 and Codabar.
- Alpha-numeric barcodes: These are also 1D barcodes. Some examples are CODE 39 & CODE 128
- 2-dimensional barcodes: These are graphical images that store information on both the horizontal and vertical planes. Some examples are QCR & Data Matrix
Any of these could be used in the lab but predominantly 1D barcodes used for tubes and plates are CODE 128 or possibly CODE 39. The other standard use barcode is the 2D data matrix barcode. The advantage of 2D over 1D is the ability to store more data in a single code and result in fewer errors deciphering codes. If using 2D barcodes, you need to ensure you have barcode scanners that can decode 2D (optical scanners).
The key disadvantage of barcodes is that they require a line of sight to be read. Barcode scanners usually must be within 15 feet or much closer to the barcode to read its data. Barcodes are typically printed on paper or plastic, which makes them easy to damage. A damaged barcode is difficult to read or cannot be read by a scanner. (Barcode scanning technology is rapidly improving, making decoding bad barcodes more successful)
Lab Instrument and Automation Barcode Scanners: These are not handheld but typically small scanners mounted to a fixed location on an automated system or are integrated internally within an instrument (plate reader, RT PCR instrument). There a variety of technologies on the market but for this discussion we will consider the three types typically used in lab automation: laser- single line, laser raster, and optical. All of these scanners work well for decoding barcodes in the right situation.
Single line laser: This is proven technology, and with a decent 1D barcode presented within the correct scan area it will decode 100% of the time. This is the least expensive option. Many automated liquid handlers and some lab instrumentation default to using this technology. Some of the downsides are that it cannot decode 2D barcodes. If the barcode is not presented within the proper scan area it will not be decoded. For example, when using a low profile assay plate (96, 384, etc.) that the skirt is only a few millimeters high, the label needs to be even shorter which results in little room to print a barcode. The margin for error is extremely tight for printing the barcode, for placement of the label on the plate, and for presenting the barcode in the proper scan area (there are similar issues for barcodes on tubes). The scan line and barcode need to match up perfectly for the decode to work. The bottom line is barcode placement as well as barcode scanner placement must be optimal with little to no deviation.
Raster Laser: These scanners can only decode 1D barcodes and the decode rate on a raster is not as high as a single line scanner. The advantage of the raster scan is that it increases the probability of an accurate read if there is a spot or void on the barcode and it allows for deviations in the placement of the label in front of the scanner. This is due to several points being scanned simultaneously. If you are purchasing an instrument such as a robotic liquid handler that comes with a barcode scanner, ask the vendor if the scanner can be a raster or, better yet, an optical scanner. Some vendors will do this for an upgrade price. It is money well spent as it will decrease many scanning issues.
Optical Scanners: This is the newest technology and offers some significant benefits. It can decode 1D and 2D barcodes. It can even decode multiple barcodes at the same time if desired. Simply put, your cell phone camera will outperform a laser scanner most of the time. The new technology in optical scanners have fewer errors and can decode poor barcodes better than most laser scanners.
|Placement of the Label||Many decode errors occur due to poor placement of the barcode. Simply put the scanner needs to be able to see/scan the entire barcode. Typical errors occur from barcode labels that are twisted/angled or wrapped around a test tube or lab plate. Improper height of the label on a plate often occurs with laser scanners. This error is seen most often when you have people or multiple people manually applying barcode labels to the tubes or plates. If your lab is typically labeling more than 50-100 plates or tubes per day, you may want to consider automating the printing and applying of the barcode. This will greatly increase the consistency of barcode placement, and quality as well as reduce labor needs by removing a manual process from your workflow.|
|Location of the Scanner||If you are planning to purchase an integrated automation system with a robotic arm and plate storage, this topic should not be an issue for you. The barcode scanner can be optimally located anywhere on the system, even on the robotic arm. On the other hand, many lab processes and the automation to accompany those processes are an evolution over time. Vendors of automation instrumentation follow no universal standard when it comes to location and placement of their proprietary integrated barcode scanner. The scanner could be located on the right, left, or even internal to a lab instrument (robotic liquid handler, plate reader, PCR instrument, etc.). It’s desirable to only have one label on a plate (north, south, east, or west side of a plate) If you have instruments with different requirements for placement, you could end up needing barcode labels on multiple sides of the plate which adds cost and time to labeling.|
|Bad Printer or Lack of Printer Maintenance||A printer that has overly used and had little maintenance or is just worn out can print bad/unreadable labels. This can cause washed out, blurred, faded, scratched, or a noisy background. An optical scanner may be able to decode some of these, but the failure rate is going to be too high if you want an end up needing barcode labels on multiple sides of the plate which adds cost and time to labeling.|
|Dots Per Inch (DPI)||Typical label printers are can have a DPI of 200 to 1200. The smaller the number the lower the resolution. The lower the resolution the more likely the barcode will be unscannable. If you are using short labels and/or small printed barcodes, go with a label printer of 600 dpi or better.|
|Bad or Wrong Labels||This issue is typically seen when someone is trying to save money on label cost. Often in the lab environment, a special material type label is needed as the plate/tube may be exposed to extreme heat or cold or a wet environment. Some of the chemicals used in the lab can also have effects on the label and printing. It is best to standardize on the best label type for your application. If you receive sample/plates from other off-site locations, make sure they are also maintaining the correct label type.|
|No White Space or Quiet Zone on Label||This can occur with 1D or 2D barcodes. The quiet zone is a blank area or margin on either end of a linear barcode where no text or other print should occur. (or the empty space around a 2D barcode. The empty space makes sure the barcode scanner does not pick up information that is not per tinent. Without the appropriate amount of white space, the barcode will not be decoded. This is usually encountered with barcodes that are too large and cover too much space on the label or are printed on the label too far to one edge, thus creating no white space at the end of the barcode. “If it’s not information you need to make a manual decision/action with the container, then do not include that information on the label”.|
|Too Much Information in the Barcode||Short answer is to keep it short. Limit the amount of information contained in the barcode to as little as possible. When using 1D code 128 barcodes, the more information the barcode contains the longer and larger the barcode. If you do need more information use 2D data matrix barcodes, as they can contain more information in a smaller space. Another suggestion is to just use generic numbered barcodes. Then use your LIMS system to correlate any specific data and information to that generic barcode. If your LIMS can do this it has the added benefit of streamlining the barcode labeling process.end up needing barcode labels on multiple sides of the plate which adds cost and time to labeling.|
|Too Much Textual Information on the Barcode||It is not unusual for lab staff/management to want a lot of text information included with barcode label. The label can quickly get crowded, leaving little room for the barcode. In this situation, the barcode becomes an afterthought and is typically too small to be decoded. For best readability, 1D barcodes require at least 2 pixels per element. 2D barcodes require at least 4 pixels for each module. The best rule to follow when including text on a label is that if it is not information you need to make a manual decision/action with the container, then do not include that information on the label.|