As automated liquid handlers (ALHs) become increasingly popular for expanding throughput and improving reproducibility, more and more labs are contemplating buying their first instrument. To help ALH buyers evaluate and select the right device we have put together a few key points.
This is one of the more obvious points, and as you may expect the amount you spend directly correlates with flexibility, throughput and ease-of-use. Instruments can range from less than $10K to more than $250K, with device size and the complexity of what you can accomplish reflected in the price.
Making sure your laboratory can accommodate a specific ALH is another obvious consideration, but there is more to think about beyond the horizontal and vertical dimensions of the instrument itself.
Consider your workflows
When thinking about possible positions for a new ALH, examine your lab’s organization. Locate sample and reagent preparation stations as well as where the samples will go after the automated steps are performed, and place the ALH in close proximity to both. We have had great success increasing efficiency in our labs by taking a LEAN approach to organization, and the introduction of a new instrument is an excellent time to re-evaluate your setup. You can apply LEAN principles to the lab as a whole as well as to individual bench tops.
In addition, many laboratories use mobile tables to maximize flexibility of tasks and workflows. All mobile tables are not created equal. Some are designed for heavy devices and some are not, so make sure the table you are considering can handle the weight, movement of the robotic system, and the required utilities.
When designing the deck layout you will need to think about overall speed, minimizing contamination by avoiding passing over clean labware (e.g., tips, plates, reagent reservoirs), location of light-sensitive materials with respect to direct light, whether to complete each assay before moving to the next or to work in batches, how easy it is to replace consumables during a run, temperature zones within a deck that has other components like incubators or readers, etc.
Consider the local environment
Because the environmental conditions experienced by your ALH can affect the reproducibility of your results, especially when working with small volumes (<10 µL), you will want to choose a location for your ALH that has stable temperature, humidity, air flow, and light (both sunlight and ambient). This is because changes in temperature, humidity and pressure can alter the accuracy and precision of pipetting (Figure 1). In addition, with most plates left open on the ALH deck, the air flow from vents and temperature fluctuations from sunlight can lead to a gradient of evaporation across wells in an individual plate (see our poster on Troubleshooting Automation).
Will ALH users be expected to write their own scripts or will they need the simplicity of pre-built programs that can be activated with the touch of a button? Will the ALH be used in different ways by different people and need the ability to store multiple programs and/or have multiple logins?
Making a list of different users, their capabilities, and their workflows can help you choose an instrument that can meet the needs of all.
At its most basic, an ALH consists of a deck to place source reagents, samples, and plates, and a pipetting head to transfer liquids. However, there are additional attachments and capabilities that enable automation of virtually any workflow.
Choosing a pipette head/pipette format
There are a number of different pipette head formats, with the most common being 8-channel, 96-channel, and 384-channel.
8-channel pipette heads are ideal when you need flexibility and are often used for serial dilutions, hit picking, and reformatting.
96- and 384-channel pipette heads enable dramatically high throughputs and are typically used for plate stamping, plate washing, and full or partial plate transfers.
When choosing your pipette head be sure to check out the manufacturer’s specifications. In addition to ensuring that the specifications will support your assays, remember that they are typically only guaranteed with the manufacturer’s tips, so be aware that you may not meet those specifications if you use another brand of tips.
Choosing a pipette head/pipette format
If you do use another brand, be sure to qualify each lot (Figure 2), since small variances in tip quality and design can affect the quality of the liquid transfer.
In addition, whichever pipette format you choose, remember to budget the time and resources for calibrating each channel in the pipette head. You have several options for calibrating a liquid handler. Whether it is a manual pipette or an ALH, each method has its pros and cons. Low liquid volumes and non-aqueous liquids require special care in the calibration routine.
You will get the most accurate and reproducible performance from your ALH if you optimize the liquid class for every liquid transfer step—learn more about optimizing liquid classes here.
When considering the assays you will be automating on your ALH, write out what happens at each step. You may be able to configure your new ALH to include the needed capability by adding a device like a plate gripper, incubator, wash station, plate shaker, magnetic separator, cooler, and more.
Automated liquid handlers are a great way to increase productivity as well as reproducibility, and the wide range of available instruments can support many of the most common workflows in life science labs. Methodically thinking through the different aspects of workflows, users, locations, and budget will ensure that your lab reaps the full benefits an ALH can deliver.