Parker has designed a new syringe pump that provides outstanding low volume, non-contact dispense performance. This long life pump can deliver a minimum of 5 million cycles, in a lightweight and compact solution, helping to reduce overall instrument costs and footprint. The 30mm Smart Syringe Pump offers best in class performance for systems that require ultra-precise fluid delivery.

Kempton Park, October 2014 - Most instrumentation used to analyse liquid samples in laboratories requires some sort of fluid delivery system to introduce the sample into the instrument. The precision of this operation is critical as errors in sampling can often lead to errors in the final results. The addition of reagents to the sample is often required in a similarly precise manner. It follows that instrument manufacturers seeking to achieve the necessary precision need to use a highly capable fluid delivery system.

Dispensing small volumes down to low microlitre and nanolitre levels creates a problem for existing fluidic systems. This is because the fluid dynamics of small volumes can lead to issues with ensuring that the entire liquid volume being dispensed makes its way into the target vessel. Small volume dispensing tends to mean that sample droplets are retained on the end of the probe, compromising precision.

While the syringe and piston pumps used by instrument manufacturers can typically deliver larger volumes well with good liquid ejection from the probe tip, they struggle in ranges of 10 µl and lower. Many of these pump systems lack the required resolution to deliver small amounts of liquid precisely.

Most syringe and piston pumps utilise stepper motors to drive the syringe plunger or piston. However, stepper motors are limited in their resolution, which is measured in how many steps the syringe or plunger length can be divided into. Most are limited to between 20,000 and 30,000 steps (full stroke).

As a result, the strategy to improve small volume performance would appear to constitute the use of a small volume syringe barrel or liquid head. This leads to issues with priming the pump as bubbles tend to adhere to the small passageways inside the barrel or liquid head. A more serious limitation emerges as the system is called upon to eject the droplet from the end of the probe. Such small volumes limit the velocity of liquid being moved and do not create enough momentum and deceleration to overcome the surface tension that retains the droplet.

The solution is to use a larger volume syringe barrel or liquid head – typically 500 µl or larger. This creates enough fluid velocity behind the dispensing action, assuming the acceleration, running speed and deceleration of the motor is rapid enough to clear the droplet with precision. However, attempting to do this with existing stepper motor driven pump technology creates two issues: first, using a larger volume syringe or pump head means that the resolution of the pump will limit its ability to precisely deliver the correct amount of liquid at low dispensing volumes; and second, stepper motor technology is not capable of high enough acceleration, running speed and deceleration to reliably eject the droplet, leading to poor fluidic dispensing performance.

A further issue arises in that syringe and piston pumps are mounted deep in the instrument (due to their size) and use long transfer lines (around 1 m) to transport fluid to the probe. Unfortunately these transfer lines rob the pump of fluid metering performance, increase wasted liquid and decrease throughput.

Aware of the issues, the Precision Fluidics Division of Parker Hannifin Corporation recently interviewed an extensive list of laboratory instrument manufacturers to understand their needs. The result is the Parker Smart Syringe Pump, which utilises standard 30 mm syringe barrels but is one third the size and weight of competing syringe pumps and its life cycle is rated to a minimum of 5 million cycles.

Rather than a stepper motor, the pump makes use of a high torque-tuned servo motor with a wide speed range to drive the syringe plunger. The encoded servo motor generates 228,495 steps of resolution (full stroke).

The servo motor on the Parker Smart Syringe Pump is also capable of much higher acceleration, running speed and deceleration than stepper motor driven pumps. This combination means it is possible to use a large volume syringe barrel to obtain sufficient flow velocity behind the dispensing action to eject the droplet reliably. At the same time there is enough resolution to deliver the right amount of fluid to the desired site at high throughput and precision.

To prove this performance, Parker obtained 30 mm (half height) syringe pumps from the three leading manufacturers and compared their respective performance with the Parker Smart Syringe Pump. The models selected were capable of the highest level of precision among their respective product lines.

The systems were set up and optimised to give the best performance for low volume, non-contact dispensing. The pumps were also run at the maximum resolution possible to give the best precision performance balanced with motor torque availability. The same probe and 1000 µl syringe barrel was used with each of the pumps with one exception which required a different barrel plunger thread to interface with the particular pump.

The Parker Smart Syringe Pump showed a clear advantage in the precision of dispenses when connected the same way as the three competitor pumps using a 1 m transfer line. The Smart Syringe Pump also showed it could also deliver small volumes with greater precision when the transfer line was eliminated by mounting the probe directly on the pump.

The improved resolution, fluid velocity and deceleration characteristics of the Parker Smart Syringe Pump enables laboratory instrument manufacturers to quickly and reliably perform non-contact dispensing of small liquid volumes. The small size and weight of the pump also allows engineers to simplify the fluid circuit by eliminating the transfer line and its associated disadvantages, aiding reductions in the size of instruments being developed.

ENDS

About Parker Hannifin Corporation
With annual sales of $13 billion in fiscal year 2013, Parker Hannifin is the world's leading diversified manufacturer of motion and control technologies and systems, providing precision-engineered solutions for a wide variety of mobile, industrial and aerospace markets. The company employs approximately 58,000 people in 49 countries around the world. Parker has increased its annual dividends paid to shareholders for 57 consecutive fiscal years, among the top five longest-running dividend-increase records in the S&P 500 index. For more information, visit the company's web site at www.parker.com, or its investor information web site at www.phstock.com.

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October 2014    Ref: AUGE063A

Hydraulics