Small-diameter tubes are commonplace in today’s laboratories. They’re used for everything from collecting blood for quick point-of-care tests like hematocrit measurements to separating tiny samples through microcentrifugation. Labeling small-diameter tubes is essential to their performance—ensuring identification, traceability, and compliance.
The tiny size and curved surface of small-diameter tubes make labeling a challenge. Labs will want to consider factors like barcode format, label construction, and application when selecting a solution for their facility.
The Necessity of Reliable Small-Diameter Tube Labels
The modest size of small-diameter tube labels belies their significance. Labels play a critical role across operations, supporting everything from workflows to regulatory compliance. For example, small-diameter labels allow for easy sample identification, offer lifecycle traceability, provide chain-of-custody, enable automation, and meet regulatory standards.
The physical constraints of the limited usable area and curved surface of small-diameter tubes present several labeling challenges. However, understanding these obstacles can help you make informed decisions about what label solution will help streamline your workflows, safeguard your data integrity, prevent costly delays, and ultimately enhance your operational efficiency.
Barcode Symbology for Small-Diameter Tube Labeling
Small-diameter tubes offer limited space for labels. Consequently, information such as barcodes, human-readable text, logos, and regulatory-required information all compete for valuable space.
2D Barcodes
The best barcode symbology for your lab depends on factors such as how much data you need to encode, your scanners, industry standards, and lab process. 2D barcodes are a popular choice for use with small-diameter tubes, with DataMatrix being the most widely used. DataMatrix codes take up less space than linear 1D barcodes and offer:
- A compact footprint that takes up minimal space or can be placed on a tube cap.
- Significantly higher data capacity than 1D barcodes, so you can encode more information.
- Omnidirectional scanning, which allows barcodes to be read from any angle and supports automation.
- Strong error correction that enables scanners to read barcodes damaged or partially obscured by frost.
A common hurdle of using 2D barcodes on small-diameter tubes is that they require special scanners. Another is the bowtie effect, which is the distortion of the code when placed on a curved surface and can lead to scanning failures.
1D Barcodes
2D barcodes continue to make inroads into lab workflows, however 1D barcodes are prevalent in lab applications. 1D barcodes, also known as linear barcodes, encode information in a single row of parallel bars to support identification, asset tracking, and inventory control.
For lab applications, Code 128 is one of the most common 1D barcodes. Code 128 uses checksum validation to help ensure accurate scanning, and its required human-readable text enables manual verification. Code 128 is most often used in manual workflows, for example, handheld scanning.
1D barcodes like Code 128 are less prone to distortion when wrapped around the curved side of a label, which facilitates easier scanning. They’re also typically more compatible with older systems, which may not have scanners capable of reading 2D barcodes.
Multi-Code Strategy
Because both 1D and 2D barcodes offer unique advantages, many labs employ a multi-code labeling strategy for their small-diameter test tubes. For example, placing a 2D DataMatrix code for machine readability on the tube cap and a 1D Code 128 on the tube side for handheld scanning and data verification.
Small-Diameter Tube Label Placement
The diameter of small tubes requires careful label placement to avoid interference and keep automated workflows running smoothly.
Avoid Overlap
Small-diameter tubes have limited surface area and curvature not encountered on larger labware. As tube diameters get smaller, the margin for error for the physical placement of labels also shrinks. For example, too-large, misplaced, or misaligned labels can overlap and obscure key information or affect how a barcode presents to a scanner.
Quiet Zone
Barcodes require a quiet zone for smooth scanning—that is, a blank area on either side of a linear 1D barcode and on all four sides of a 2D barcode. On small-diameter tubes, labels can encroach on the required quiet space, negatively affecting scanning reliability. When engineering lab labels, it is important to account not just for a label that fits on your tubes and conveys critical information, but also one that leaves enough empty space for efficient scanning.
Tighter Tolerances
When labels get smaller, so does the room for sub-standard labels. High print quality with strong contrast between the barcode and background is vital. The barcodes themselves must have sufficient module density—or more simply, be large enough—for your scanner’s resolution. It’s also important to print on the proper material. For example, glossy and transparent surfaces can introduce glare and lead to scanning errors, particularly in high-throughput automated systems.
Optimize for Automation
High-speed automated lab systems using robotic handling, automated storage, rack readers, and sample-picking systems depend on barcode labels for everything from routing to testing to storage. To ensure automated systems work at their best, apply barcode labels to the same location on every tube. Inconsistent label placement can lead to scan errors, incorrect routing, and additional handling—all of which hurt your lab’s productivity.
Other Small-Diameter Tube Label Considerations
The environment your labels will operate in, from workflow to conditions, also plays a significant role in selecting the right label for your operation.
Cryo Resistance
If your lab exposes small-diameter tubes to ultra-low-temperature freezers or liquid nitrogen, consider cryogenic labels, such as the CryoLabel® line from Electronic Imaging Materials (EIM). Our CryoLabel® range can withstand temperatures as low as -196⁰C and stay securely adhered even after repeated freeze-thaw cycles.
Chemical Resistance
Small-diameter tubes are often exposed to a number of harsh chemicals, including ethanol, isopropanol, xylene, and bleach. Chemical-resistant labels, like our XyResist® labels, can withstand these aggressive solvents and remain securely attached and legible through your lifecycle.
Abrasion Resistance
Automated lab systems are tough on labels. Robotic grippers, rubbing in racks, decappers, and frequent handling can all scuff and scratch barcode labels, rendering them illegible and unscannable. Robust facestocks, high-quality printing, and protective topcoats can all help labels thrive in demanding lab workflows.
Testing
Labs are experts at testing the samples that move through their facility. That same rigor should extend to their labels. Before committing to a full run of labels, validate their performance in your workflow to see how they stand up to the real-world conditions they’ll face. At EIM, we love to talk with lab customers about our industry-leading labels. We also love when labs request samples. It allows us to show just how exceptional our label solutions are.
Electronic Imaging Materials, Inc.
Have questions about small-diameter tube labels or other hard-to-solve lab labeling issues? The Label Experts are here to help. Contact us and leverage our nearly four decades of labeling experience to optimize your labels and, in the end, your operation.
