Automated Pipette: Liquid Handling System

By Ashma Shrestha •  Created: 07/10/22 •  6 min read

A pipette is equipment that helps measure and dispense liquid materials of desired measurements in any laboratory. Since almost all science laboratories require precise and accurate liquid measurement for their experiments, the pipette is used widely.

Automated Pipette
Solo Liquid Handler by Hudson Robotics

An automated pipette or automated liquid handling system is a pipette operated by software that commands a pipette/robotic liquid handling tool to aspirate the desired amount of sample and dispense it into the required container. Although these pipettes provide automated aspiration and dispensation, changing pipette tips, and placing and holding trays can be either automatic or manual. Commonly, automated pipettes are called liquid handling robots.

Liquid Handling System

There are various systems for handling liquids. Pipettes are one of the liquid handling systems. These can be manual, semi-automatic, or automatic. 

The manual pipetting requires calibrating the pipettes, entering the desired volume in the pipette, and aspirating and dispensing the liquid by laboratory workers. It works best for laboratories dealing with small sample volumes because only a sample is processed at a time.

The semi-automatic pipettes require user intervention during moving the plates/tube in-between steps or exchanging the tips but not during aspiration and dispensation. It provides handling of 10-100 samples at a time depending on the types. The pipettes can have a single channel or multiple channels for liquid handling.

The automatic pipettes or robotic liquid handlers have robotic arms for moving the plates/tubes and exchanging tips during experiments. Only the step of entering the desired volume in the software requires the intervention of humans, and it provides a walk-away facility. It also helps in handling more than 100 samples at a time.

Working Mechanism of Pipette

Pipettes usually work based on two mechanisms; air displacement and positive displacement. The basic principle of pipetting is to displace/dispense (pushing out) a sample volume after aspiration (pulling in). The plunger and piston control these actions. The difference in piston and displacement methods determines the types of pipettes. These methods use plastic tips for displacement.

Besides these, other methods that do not use tips are also available. The technique like acoustic droplet ejection method is one of the non-tip-based pipetting methods.

Air Displacement Method

As the name suggests, the air displacement method for aspirating a certain amount of liquid dispenses almost the exact amount of air. The air displacement method has a piston-cylinder system that helps in measurement. The piston is connected to a plunger that pushes out the air volume equal to the liquid to be aspirated. The aspiration creates an air cushion that separates the aspirated sample (liquid) in a plastic tip from the pipette piston.

With the expansion of the air in the cushion, the 2-8% extra liquid is drawn. In order to overcome the problem, proper calibration of the pipette is necessary. In addition, temperature, humidity, and air pressure of the liquid also determine the amount of air trapped which might create inaccuracy during aspiration.  

Positive Displacement Method 

The air displacement method is not applicable when handling liquid that has more density, higher viscosity, and high air pressure. Since the air displacement method lacks precision while handling such samples due to the air-cushioning, positive displacement overcomes these problems. The method’s accuracy depends on the disposable plastic tips used because these tips have integrated pistons. The piston is coupled to the piston rod of the dispensing devices. The method requires specially designed tips instead of tips from any other system.

The aspiration of liquid in positive displacement occurs by pulling the piston up rather than pushing down, preventing the formation of an air cushion. The pulling up creates a vacuum which draws the liquid into the tips.

Acoustic Droplet Ejection (ADE) Method

ADE method is an entirely contactless method of dispensing liquids. Here, placing the source of acoustics (sound energy) near the surface helps eject a small droplet of samples into the plate. The frequency of the sound determines the sample volume. 

Parts of Automated Pipette

The automated pipette has the following parts.

  • Control system: These control the movement of robotic arms.
  • Washing area: It is the place where cleaning or dispensing heads and plates occurs. 
  • Sensors: These feed information to the control systems and help maintain accuracy.
  • Dispensing heads: These control the liquid flow in the vessels.
Source: Hamilton OEM Liquid Handling

Benefits of Automated Pipette

The benefits of the automated pipette or liquid handling system are as follows:

  • Thorough output

The pipetting obtained by using automation is thorough or accurate. Unlike manual pipetting, there is a decrease in human errors because the machines carry out all the manual work.

  • Enhanced reproducibility

The automated pipetting provides increased reproducibility in the laboratory. That means the technique helps obtain consistent results.

  • Walk away facility

The machines carry out all the work, and the contamination decreases. Once the information is fed in, they can perform other laboratory duties by running the pipetting process in the background.

  • Decreased contamination

Since the machine carries out almost labor work susceptible to contamination, the risk of contamination due to human contact decreases. Likewise, continuous cleaning and maintenance also decrease the contamination. 

When to Switch to an Automated Pipette?

  • Conversion into a molecular laboratory

An automated pipette helps in many molecular techniques like sequencing and blotting because it provides precision while handling liquid samples. Also, it helps in processing multiple samples at a time.

  • One-time investment

The cost of automated pipettes is high compared to manual and semi-automatic pipettes, but it is sustainable in the laboratory that is opting for decreasing manual labor.

  • Automation 

Since many laboratories are switching to automation, an automated pipetting system is another good addition to the automation of the laboratory.

  • Processing a larger sample size

The processing of the liquid samples in your laboratory is increasing, leading to an increase in pipetting tasks. An automated pipette can pipette more than 100 samples in an hour, which helps complete the work faster with accuracy.

Limitation of Automated Pipette

The limitation of automated pipettes are as follows:

  • High installation cost

The cost of many robotic liquid handlers ranges from $1000K to $1500. This cost is almost not applicable to any smaller laboratory. 

  • High maintenance cost

The maintenance of an automated pipette needs to be carried out regularly, and the maintenance cost is also high. In addition, trained maintenance workers are scarce.  

References

Ashma Shrestha

Hello, I am Ashma Shrestha. I am currently pursuing my Master's Degree in Microbiology. Passionate about writing and blogging. Key interest in virology and molecular biology

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