Produced in Partnership with OpentronsApr 16 2024Reviewed by Louis Castel
The Opentrons OT-2 is an automated liquid-handling robot capable of pipetting difficult liquids. Molecular assays need precise pipetting reagents and samples that offer a diverse set of attributes; this includes viscous liquids that can clog tips, have uneven distribution, and complicate reproducibility.
The default parameters set in the Opentrons Protocol Python API have been optimized to handle wet reagents efficiently and accurately.
Reagents can have different viscosities, rates of evaporation, and surface tension on their list of attributes. Commonly used reagents differ in viscosity, evaporation rate and surface tension, among other properties.
This article discusses best practices for automating the handling of viscous liquids utilizing the Opentrons OT-2 based on testing with computer vision-based and gravimetric methods.
Methods
Opentrons developed the optimization strategy for viscous liquid handling by combining the specifications of the pipettes, the labware profile to be used, and the OT-2 derived from the rheological properties of the liquids.
The study was restricted to the viscous liquid handling capacity of Opentrons GEN2 Single-Channel pipettes. The liquid handling functions used were aspiration and dispensing. The parameters may not apply to mixed or formed complex liquids, and differences in workflows could mean different parameters.
Conclusion
Results from viscous testing validated that the OT-2 with Opentrons GEN2 Single-Channel Pipettes could handle liquids with a variety of viscosities, producing accurate results that are comparable to the water handling capacity of OT-2.
The optimized parameters and recommended guidelines improved the liquid handling performance of OT-2, ensuring the successful run of protocols.
The application of the viscous liquid class is demonstrated in Figure 2 and Figure 3. The lower flow rates combined with critical set times allow viscous liquids to settle. Extra steps like a slower blow out minimize the loss of viscous liquid and enable the efficient use of reagents, increasing accuracy in results.
Blow out volume can be too low or too high for liquid dispensing, requiring the addition of an air gap before aspirating the viscous liquid. A slower rate of dispensing instead of a slower blow out can achieve the required air volume to move the viscous liquid out of the tip, resulting in less liquid being aspirated than the maximum limits of the pipette.
This would not represent a suitable use for the Opentrons GEN2 P20 Single-Channel pipette. Finally, to prevent droplets from sticking on the tip and reagents from spilling in the labware, slower withdrawal speeds after aspirating and dispensing is highly recommended.
The OT-2, Opentrons GEN2 Single-Channel pipettes, Opentrons Tips and Opentrons Filter Tips can handle viscous liquids and improve protocol accuracy exponentially.
Figure 2. Strategizing an aspiration cycle with Opentrons Python Protocol API. Image Credit: Opentrons
Figure 3. Strategizing a dispense cycle with Opentrons Python Protocol API. Image Credit: Opentrons
About Opentrons
Today, biologists spend too much time pipetting by hand. We think biologists should have robots to do pipetting for them. People doing science should be free of tedious benchwork and repetitive stress injuries. They should be able to spend their time designing experiments and analyzing data. That's why we started Opentrons.
We make robots for biologists. Our mission is to provide the scientific community with a common platform to easily share protocols and reproduce each other's results. Our robots automate experiments that would otherwise be done by hand, allowing our community to spend more time pursuing answers to some of the 21st century’s most important questions.
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