Electronic pipette
For use in automated immune workstations
Pipettes are long, thin tubes used to measure or transfer small amounts of liquid. They are widely used in diagnostic laboratories throughout the pharmaceutical and biotechnology industries.
Today, medical laboratories around the world are automating more and more processes. This trend allows healthcare providers to test and diagnose a wider range of conditions in hospitals or doctors' offices, rather than sending test results to remote labs. This helps in faster diagnosis and earlier detection of health conditions. However, this level of automation also requires faster and more accurate equipment.
How do pipettes work?
Pipettes work on a principle very similar to syringes. They create a vacuum, drawing liquid into the pipette and dispensing precise volumes each time. Pipettes come in various sizes, with volumes ranging from a few microliters to hundreds of milliliters. Pipettes are typically used in sterile environments, so preventing cross-contamination is crucial. Automated immunoassay workstations utilize a large number of electronic pipettes; these systems feature cams, pistons, and cylinders.
Several of the world's largest diagnostic laboratories use HKP products to power their automated immunoassay workstations. The variety of options provides machine designers with the flexibility to make these workstations smaller, faster, and more precise.
Application Requirements
• Accuracy and repeatability: Electronic pipettes can dispense specific volumes of liquid with great precision. The resolution of a pipette is typically less than 1% error for every 1 microliter increase. Repeatability is equally important, ensuring that the exact same volume of liquid is extracted or dispensed in every subsequent operation.
• Cost savings: The ability to improve accuracy allows laboratories to use fewer reagents in their analyses, thus reducing costs.
• Efficiency and Ergonomics: Electronic pipettes significantly reduce manual labor. Once the electronic pipette is installed, users can complete filling, emptying, and ejection operations with a single click. This increases productivity and the number of samples that can be processed in a given time.
Application Challenges
• Accuracy and repeatability: Pipettes typically have a resolution of 1 microliter increment with an error of less than 1%.
• The space between multichannel pipettes is very small. This requires the motor to be less than 16 mm in diameter and generally less than 100 mm in length.
• The thrust must be greater than 8 N and the speed must exceed 8 mm/s.
• Noise and vibration must be minimized.
Solution
The selection criteria for electric motors typically include size, performance, price, and efficiency. Most engineers will choose cost-effective linear stepper products or small brushless motors.
linear stepper motor
Linear stepper motors are an off-the-shelf solution for electronic pipetting applications. The built-in screw connects directly to the piston of the electronic pipette to provide the linear motion required to operate the device. Furthermore, because it is a stepper motor, no additional feedback sensors or encoders are needed to control the motor. The stepper motor rotates with each incremental current pulse, making it easy to control. The motor's linear stroke accuracy and the possibility of microstepping provide very high resolution, matching the high demands of electronic pipettes for accuracy and repeatability. In addition, the motor can hold its position without power, thus expanding the applicability of the device. Linear stepper motors are typically used for output speeds below 800 RPM.
Stepper motor with RGS linear guide
RGS is a screw-driven guideway system that offers excellent linear speed, precise positioning, a narrow base, and long service life. It is a compact and cost-effective component. RGS length and speed are not limited by critical screw speed, enabling high rotational and linear speeds even over long spans. • A wide selection of imperial or metric conductors; • Customizable lengths > 2.4 meters; • All moving surfaces are made of Kerkite® polymers running on a Kerkote® TFE coating; • Available only as guides, screw drives, electric actuators, and electric actuators with integrated drives.
brushless motor
An alternative to linear stepper motors is a coreless or hollow-cup brushless DC motor. This option is the most efficient technology because the stator consists only of coils and shafts (instead of a cored motor). Therefore, coreless motors have no iron losses, which improves motor efficiency and acceleration. Since electronic pipettes are battery-powered, this increased efficiency extends the usage time on a single charge.
The brushless product has a diameter of 13 mm and is equipped with a small encoder, gearbox, and lead screw. It can operate at speeds up to 60,000 RPM, and its excellent output power makes it suitable for use in small spaces.
For pipetting applications, both brushed and brushless DC motors require additional components, such as belt drivers and encoders, to convert rotary motion into linear motion and to control the motor. This solution is typically used in high-end models with multiple channels.
For more information on Pittman motion solutions for automated immunoassay workstations and electronic pipettes, please contact us.
