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Increasing use of syringe pumps

Jan. 17, 2022

Syringe pumps represent a very special case in the wide range of metering pumps. They are the result of highly developed modern mechanical engineering, which now makes it possible to manufacture very high-precision gears, as well as control technology based on specific computer software. Their task is to continuously transport fluids of different viscosities in precise volumes. It all started 65 years ago with a primitive drive. Modern syringe pumps have little to do with this original equipment. In the vast majority of cases essentially continuous fluid transfer is still done using peristaltic infusion pumps equipped with sliding members. While these can achieve a constant flow rate with low pulsation, the actual volume delivered is only as accurate as the volume of the pipe with shaft rotation compression. In contrast, in syringe pumps, the continuous flow rate is limited by the flow rate of the syringe itself (1-50 mL). The main task of such a pump is the precise and constant metering of small volumes.


Increasing use of syringe pumps

 

Structure of the syringe pump

Although modern syringe pumps may have different designs depending on their field of application, they all contain the same basic components: the syringe holder, the threaded shaft that drives the syringe plunger, and the control program. In most cases, the spindle drive can deliver a continuous volume with a tolerance of typically + 2%. The actual volume of fluid delivered depends on the predefined drive speed as well as on the volume of the syringe. Thus, the decisive factor is the distance the syringe plunger must travel in a given time to achieve the desired fluid flow at the syringe volume used. Absolute volume control is achieved by means of the direct displacement principle.

In modern pumps, many parameters can be selected and adjusted. In principle, syringe pumps can also be used in suction mode. It is important to note that the transferred media are never in contact with the mechanical pump assembly. Instead, they are located in a closed syringe system. The different syringe sizes are easily interchangeable, so syringe pumps can be used for a variety of applications. There are also devices that allow for multiple arrangements of up to 10 syringe pumps. In addition to high-precision pumps, mention must also be made of high-pressure syringe pumps, which can be used for all technical applications requiring pulsation-free, precise metering of specific delivery media, such as high-viscosity solutions.

However, syringe pumps should not be used for human medical applications without proper authorization. Infusion syringe pumps suitable for pump design and operating at infusion rates typically between 0.01 mL/h and 200 mL/h are authorized for such applications. Output options (e.g. mL/h) can be freely selected. Various alarm functions are also available, such as bubble detection in the case of an infusion pump. Due to the need for power, it may sometimes be necessary to use a rechargeable battery to operate the pump if the entire unit must be removable.

Recently, low-pressure syringe pumps that can deliver very small volumes of 0.005 µL/h with high precision have become available.

 

Application areas of syringe pumps

Syringe pumps are now used in many other applications, especially where precise metering is required.

Modern syringe pumps are also used in the field of medicine and pharmaceutical research. They are of particular value when volumes in the µL range must be dispensed precisely, for example in order to add minute concentrations of active ingredients during experiments or to mix very small amounts of reagents.

As examples of typical applications, the manufacturer of syringe pumps lists, for example, the intravenous administration of products in animal experiments, the dispensing of adhesives, the use of filling systems, or, more generally, all types of mixing processes. For the purpose of biological research, the Ruhr-University Bochum has developed an electrochemical robotic system for the implementation of electroanalytical methods and bioassays on micro-titration plates and, more generally, for the study of biological problems that also involve the use of syringe pumps.

It is also known that syringe pumps, especially those operating at high pressures, are also used for transporting chemicals, feeding reactors or for use in the field of catalysis. The requirement is always to be precise and to provide a stable, pulsation-free flow. High-pressure, high-temperature syringe pumps that can achieve low flow rates - i.e. pumps equipped with heatable syringes - are suitable for core repulsion experiments.

Gas-tight syringes can now also be used to perform specific microvaporization operations, for example in microchip manufacturing.

The use of syringe pumps capable of delivering very small fluid flows in the nL range is growing significantly. In the fields of microfluidics (the behavior of fluids in very small spaces), flow chemistry (reactions in continuously flowing fluids), and microreaction technology, the pulsation-free nature of the resulting fluid flow is extremely important.

In instrumental analysis, syringe pumps are used to implement chromatographic methods in the field of HPLC (High Performance Liquid Chromatography) and LC-MS (Liquid Chromatography/Mass Spectrometry) in order to minimize background noise during electrochemical detection with high precision and stable transport of the mobile phase.

Finally, it is also necessary to consider another extremely important field of application. When performing analytical examinations at very low concentrations, it does not make sense to use normal dilution methods to prepare the stock solutions required for calibration. In this case, syringe pumps capable of dispensing very small volumes (µL or nL) of solutions with known, analytically controlled elemental ratios with high precision are well suited. This should eventually make it possible to develop reference processes for use in specialized areas of nanotechnology or in the life sciences.

 

New syringe pumps

The Hedy syringe pump is designed for metering different fluids in the microliter and nanoliter range. Mechanical highlights are the gearless stepper motor for the carriage drive, the high precision carriage itself, the adjustable syringe holder and the resulting possibility to change syringes. The extremely high resolution of 25,600 steps per revolution makes each step imperceptible, while ensuring accurate delivery of 4 pL per pulse when using standard syringes. the total volume delivered varies between 0.5 nL and 44 mL per minute, depending on the volume of the syringe used. Both disposable and metal-free precision syringes can be used in adjustable holders as needed. If multiple different fluids need to be dispensed, up to six units can be operated on a single USB interface, and this number can be doubled as an option. Individual units or entire systems can be configured from a PC.

Use the software-controlled three-way valve to switch between metering and fill or aspiration modes, allowing refilling of the syringe without removing it from the adjustable holder. Dosing operations can also be initiated using a foot switch so that the operator always has both hands free.

With the software, the Hedy syringe pump is even more versatile. A basic function is the individual adjustment of the flow rate during dosing and filling. In addition, it is possible to set the units of continuous fluid delivery for a given time period, or to specify the minimum delivery volume for each individual step. This also applies to automatic repeat cycles of the syringe, rest periods, emptying and filling levels, and control of solenoid valves.

The software and firmware can be updated via the Internet. the Hedy syringe pump is a state-of-the-art device that can be used in a wide range of applications in R&D as well as in industrial practice.