Automated pipetting: everything you need to know

What is automated pipetting?

Pipetting is the transfer of pre-determined measured volumes of liquid from one container to another. Typical to most modern laboratories, the micropipette was invented by Heinrich Schnitger in 1958 (1). Using a piston-stroke mechanism, micropipettes are manually operated by laboratory personnel to transfer small volumes of liquid. Automated pipetting, however, functions with a motorised pipetting system to perform the aspiration and dispensing of liquids into designated vessels, without the need for user interaction.

What is an automated pipette used for?

Often called ‘liquid handling robots’, automated pipetting systems are used to speed up the process of transporting small and precise volumes of liquids. Automatic pipettes can be programmed to set protocols for aliquoting, mixing, and serial dilution of liquid samples, to provide highly accurate and repeatable assay results.

What are the main components of an automated pipetting system?

Whilst there is some variation between different instruments, most automated liquid handling systems contain the following components.

Pipetting head

The pipetting head is where the liquid transfer occurs, using either single or multiple channels of pipette tips to transfer the liquid between vessels.

Control centre with a user interface

Movement of the robotic components that make up the automated pipetting system is controlled via the control centre. The unit will usually include a user interface that allows the operator to configure programmes and monitor the progress of the experiment.

Mechanical motors and actuators

Motors within the liquid handling instrument precisely control the placement of the pipetting head and other robotic elements, and actuators are used to govern the flow of liquid.

Working/substrate deck

A working area (also known as a substrate deck) is the allocated space within which the pipetting head can move around to aspirate and dispense the liquid into plates (or other containers) that are placed in a pre-defined location.

Pipette tips

The pipette tips are where the liquid is held once it has been aspirated. Automated pipette tips can be fixed onto the pipetting head permanently, or they can be disposable, depending on the intended application of the automated pipetting system and thus the consequence of cross-contamination.

Waste

A disposal system for waste by-products (e.g. disposable pipette tips or unwanted liquid) is incorporated into the system to achieve a fully automated, efficient operation (2).

What is the difference between manually-operated, semi-automated and automated pipettes?

Manual pipetting involves the transfer of small volumes of liquid by micropipette. Whilst this method can be useful for one-off procedures, you are limited to a low throughput of samples for simple experiments. There is a time and cost penalty associated with manual pipetting, as researchers are confined to performing tedious pipetting tasks by hand, rather than conducting higher-value experiments.

Manual pipetting incurs the greatest risk of variability between assays and researchers, as each operator will likely use a slightly different pipetting technique. For example, there will be discrepancies in the orientation of the micropipette, the speed at which the liquid is dispensed, and whether a reverse or forward pipetting technique is performed. At every stage, variation is introduced into the system and the final results can be highly erroneous.

A semi-automated pipetting instrument is the incremental next step toward a fully automated liquid handling system. For example, a semi-automated pipette may include a control centre to govern the aspiration/dispensing of liquids, but the pipetting head may still be hand-operated. These types of systems relieve researchers from manually setting volumes and operating the aspiration/dispensing, and they instead simply transfer the pipette head between containers.

Semi-automated pipettes ensure a lower risk of variation between researchers and thus enhance the reproducibility and reliability of experiments. A slightly higher throughput can be achieved with these semi-automated instruments, however, there is still a requirement for user intervention. Similarly to manual pipetting, researchers are not protected from handling hazardous samples, and there is still a proportion of researcher time wasted in the manual operation of the pipetting head.

A fully-automated pipetting system allows for high throughput liquid handling without the need for user intervention, eliminating the inconsistencies associated with manual and semi-automated pipetting.

Benefits of automated pipetting

There are many benefits associated with the use of automated liquid handling systems, in comparison to semi-automated or manual pipetting, including higher productivity, enhanced reproducibility, and a more efficient workflow.

Increased throughput and productivity

Using an automated pipette allows for the processing of more than 100 samples an hour, a significantly higher throughput than manual or semi-automated pipetting. Laboratory personnel can be more productive with their time, often having greater job satisfaction as the mundane pipetting tasks are now automated.

Improved reproducibility

Despite the high throughput, automated pipetting does not compromise on data quality. Automated liquid handling greatly enhances the reproducibility between assays, as monotonous pipetting tasks can be repeated without the robotic system tiring or deviating from its programmed operation, reducing the variability between scientists and assay repeats.

Efficient workflow

Manual pipetting can consume over 80% of a researcher's workday. In contrast, automated pipetting systems operate without the need for human intervention, alleviating the pipetting bottleneck and freeing up laboratory staff to perform more innovative research. The workflow of laboratory processes is made more efficient, saving on time and costs, and can even continue running on a 24/7 basis if required.

Handling of hazardous/precious samples

By completely removing the requirement for human interaction with the pipette head and/or tips in liquid handling automation, hazardous and precious samples can be safely pipetted. The transfer of liquids can be completed without concerns over the risk to the researcher, or the risk of losing important samples. The danger of laboratory staff developing repetitive strain injuries associated with manual pipetting is also eliminated (3).

Are automated pipettes accurate?

The precise control over the programmable automated liquid handling instruments means that they are able to be extremely accurate. Without researcher-to-researcher variability, the aspiration and dispensing of small volumes of liquid can be performed identically across assays, with high precision and accuracy.

Applications of automated pipetting

Automation is now a significant component of the workflow of many laboratories around the world, as scientific innovation becomes increasingly rapid. There is a growing demand for reliability and scalability of experiments, particularly in cell culture and genomics-focused laboratories, where sample preparation has become a considerable bottleneck. In such laboratories, there is a large proportion of routine practices that have the potential to be automated, for example, high throughput next-generation sequencing (NGS) for cancer genomics research.

It has been reported that UK laboratories take at least 6 days to complete NGS for genomics analysis, likely due to the fact that library preparation for NGS can consume 8 hours of hands-on time for one researcher (4). The use of benchtop automation can automate pipetting for genomics. Integration of an automated liquid handling system into the sequencing workflow would ensure a more time-efficient and cost-effective process, whilst improving the accuracy and reproducibility of results.

There are also benefits of automated liquid handling in cell culture laboratories. The precision of automated pipetting means that, for example, more than 95% of cells, when using liquid handling robots to aspirate cell media, will be retained (3). An automated pipetting system can provide a high throughput, streamlined ecosystem when embedded into a cell culture workflow. Job satisfaction will be boosted, as researchers can be reallocated to more fulfilling tasks, and productivity will rise as the sample preparation bottleneck is relieved.

Which pipetting system is right for my lab?

Pipetting systems range from manual pipetting, using micropipettes that are hand-operated by researchers, to highly sophisticated automated liquid handling instruments. If you want to optimise your laboratory workflow, with a high throughput sample processing ecosystem and more efficient use of researcher time, then integrating an automated pipetting system could prove a valuable choice. Manual pipetting can be useful for simple one-off procedures with low throughput, however, they lack the reproducibility and reliability of an automated system.

How to choose an automated pipetting system

In order to choose an automated pipetting system for your laboratory, there are several common considerations that must be taken into account:

Workflow. Consider the type of liquid that is required for aspiration/dispensing and its associated properties (e.g. viscosity and volatility), and whether tubes, plates or other accessories are to be used as containers.

Scale. Discuss whether single or multi-channel liquid handling is needed for the desired application.

Modularity. The need for additional equipment (such as plate shakers, heating blocks, centrifuges etc.) should be considered, as these extra components could allow the operation of many other functionalities that will enhance your workflow.

Programming. The complexity of the system should be contemplated to decide whether liquid handling is only required for a fixed, specific operation, or whether the ability to programme a multitude of tasks would be more appropriate.

Size. Practically, bench space in the laboratory must be considered, despite most liquid handling robots only requiring < 0.5 m². Space, however, can be more restrictive in the case of cell culture laboratories in which cross-contamination must be carefully managed.

 Cost. Automated liquid handling instruments can have a higher initial cost than the alternatives, however, the time and cost efficiencies could make up for the initial investment over time.

Automata’s modular lab automation solution can automate other manual processes such as plate handling, sample preparation, and more.

Further pipetting FAQs

What are the largest sources of pipetting problems?

Transportation of the pipette from aspiration to dispensing location. The force of the movement can influence the equilibrium between the liquid and air inside the pipette tip, inducing the formation of a small drop on the end of the tip.

Viscous liquids. Liquids that have high viscosities are particularly challenging to pipette manually, especially when it comes to dispensing the liquid into its desired new container. Often the blowout volume is not sufficient to dispense all the liquid from the tip.

What are the common pipetting errors, and how can automated pipetting prevent these?

Swap speed. The speed at which the pipette tip is removed from the aspiration liquid needs to be slow enough to remove excess liquid from outside the tip.

Settling time. A wait time is required for the liquid and air in the pipette tip to reach equilibrium before the liquid is dispensed.

Dispense velocity must be high enough to ensure a ‘clean cut’ between the dispensed liquid and the liquid that is retained within the pipette tip.

Orientation. Ideally, a vertical orientation of the pipette tip in the aspiration liquid should be used.

All of the above errors can be prevented by using automated pipetting, as liquid handling robots can be programmed to incorporate specific speeds, wait times and orientations into their protocols (5).

What is an acceptable error for pipetting?

There are systematic and random errors associated with pipetting, both of which can be reduced by removing user intervention (i.e. automated pipetting). For example, when properly calibrated 1000 μL micropipettes should not exceed ±8.0 μL (systematic error) and ±3.0 μL (random error).

Automated liquid handling robots include programmed quality control checks and calibration testing, ensuring that the systems are always operating to optimal performance.

Is an automatic pipette more accurate than a measuring cylinder?

Automatic pipettes are more accurate than measuring cylinders. Measuring cylinders use a subjective determination of volume conducted by eye.

Whereas, automated pipetting is set to a precise protocol that accounts for every drop of liquid. Typically, measuring cylinders are used for much larger volumes than pipettes as their inaccuracy becomes more significant as volume decreases.

What are the different types of pipetting techniques?

There are two different types of pipetting techniques: forward and reverse pipetting. Forward pipetting aspirates and dispenses the desired volume of liquid with a blow-out volume of air used to expel the remaining liquid in the tip.

In contrast, reverse pipetting aspirates a larger volume of liquid than desired, and dispensing expels only until the first stop, leaving the excess liquid in the pipette tip. Reverse pipetting is usually used for more viscous substances (6).

Refrences

1      Labmate, A Brief History of Pipettes and Liquid Handling, https://www.labmate-online.com/news/laboratory-products/3/breaking-news/a-brief-history-of-pipettes-and-liquid-handling/57036, (accessed 6 December 2022).

2      Automated Pipetting Systems - Comparison Guide | SPT Labtech, https://www.sptlabtech.com/automated-pipetting-the-complete-guide, (accessed 5 December 2022).

3      A. aurorabiodev, Beginner’s Guide to Understanding Automated Liquid Handling, https://www.aurorabiomed.com/beginners-guide-to-understanding-automated-liquid-handling/, (accessed 6 December 2022).

4      H. Tegally, J. E. San, J. Giandhari and T. de Oliveira, Unlocking the efficiency of genomics laboratories with robotic liquid-handling, BMC Genomics, 2020, 21, 729.

5      What are the common pipette handling errors?, https://capp.dk/blog/common-pipetting-errors/, (accessed 7 December 2022).

6      Forward, Reverse, Repetitive, & Heterogeneous Sample Pipetting | Thermo Fisher Scientific - UK, https://www.thermofisher.com/uk/en/home/life-science/lab-plasticware-supplies/lab-plasticware-supplies-learning-center/lab-plasticware-supplies-resource-library/fundamentals-of-pipetting/proper-pipetting-techniques/forward-reverse-repetitive-heterogeneous-sample-pipetting.html, (accessed 7 December 2022).