This blog post provides a summary of the application note: A Guideline for Operating Micropumps at Low Flow Rates.

The Bartels mp6 micropump is a piezoresistive diaphragm micropump targeting flow rates up to 7 millileters per minute (ml/min) for liquids and 18 ml/min for gases with no backpressure and 600 mbar maximum pressure at no flow. Users can adjust the pumping rate by modifying the amplitude and frequency. 

To achieve low flow rates, the user should lower the amplitude. The consequence of doing this without a restrictor is that the generated pressure levels are also lowered which may be unsuitable. A minor pressure raise could also cause clogging since the maximum backpressure is too low to overcome. When a restrictor is applied (preferably to the pump exit), the flow rate is reduced by the fluidic resistance. That means with the maximum amplitude and optimal frequency, the flow rate is only as high as the restrictor allows. The pressure generation of the pump is the same as without the restrictor. (see the chart below).

The restrictor can be a short piece of narrow tubing (capillary) for a simple application or a precision orifice with an exact inner dimension. The application note focuses primarily on using capillaries as the user can adjust the flow rate by changing the length. Orifices come in preset dimensions - diameter and length - and it may not be possible to find the correct orifice for a specific flow rate.

Calculating the correct restrictor can be done by treating the pump as an electrical circuit, calculating the internal fluidic resistance of the pump, adding the restrictor as a resistor and applying the law of Hagen-Poiseuille to determine the resistance. The maximum flow rate is dependent on the total resistance of this system. Detailed steps are available in the application notes.

Once the restictor is finally set, it is then possible to vary the flow rate by changing the amplitude from the new restricted max flow to zero. The full range of the amplitude allows smaller flow rate steps with voltage changes than with the unrestricted pump. See the calculation results in the example below based on an mp6 pumping water.

Possible capillary material includes PEEK tubing and polyimide (PI) tubing which is available in a wide variety of diameters and is readily available from many suppliers. PEEK and PI material are resistant to a wide variety of pumping media.

Download the complete application note

Visit the mp6  micropump specification page

The mp6 micropumps from Bartels Mikrotechnik GmbH are suitable for pumping liquids and gases for a variety of different applications. Here we are highlighting the use of the mp6 in a germ detection device used in hospitals.

Bartels and the Austrian Gesundheits-Cluster Oberösterreich worked together with the project goal being the automation of "Genspeed", a medical system for fast diagnosis of hospital germs of Greiner Bio-One International AG. The newly developed on-spot instant diagnosis device "Genspeed R2" is able to verify the existence of different infectious germs - including, among others, antibiotic-resistant bacteria such as MRSA at the human body - from different samples within 75 minutes.

Technological core elements of the device are a microfluidic-chip and a miniaturized automated dispensing system based on the mp6 micropumps. Different reagents can be disposed with microliter accuracy into the inlet opening of the microfluidic chip. The controlled liquid volumes are precisely applied in the correct succession with testing results shown on a computer screen. This method delivers results much faster than the traditional diagnosis chain of sending a sample to a laboratory. This is a perfect example of the capability of microfluidics in respect to optimization of standard processes, reduction of waiting times - and therefore costs - as well as improving patient treatment response times. This system uses 3 mp6 pumps and 1 mp6-oem controller.

Learn more about the mp6 micropump and also try our product & pricing guide for micropumps.

Since the end of 2012, Servoflo has been selling the mp6 micropump, made by Bartels of Germany.

This unique micropump focuses on pumping up to 7 ml/min of water and 18 ml/min of air/gas. Other liquids can also be pumped. Typical applications for the micropump include medical drug delivery, cell culturing applications, fuel cells, consumer, nebulizers and much more.

mp6 micropumpThe functional principle is based on a piezoelectric diaphragm in combination with passive check valves. A piezo ceramic mounted on a coated brass membrane is deformed when voltage is applied. By the resulting down stroke, the medium is being displaced out of the pump chamber below. The check valves on both sides of the pump chamber define the flow direction. 

The response to this product has been tremendous, and we are excited about the many new possibilities for this interesting product.

Bartels has release 4 new tech notes to assist customers in their use of the pump:

Amplitude and Frequency Effects on Flow Performance - Based on the diaphragm pump principle, themp6 has a typical flow and pressure performance. By controlling the piezo actuator deflection, the performance can be varied. The amplitude determines the height of the piezo deflection and thereby the displaced volume and the frequency the number of deflections.

Running Multiple mp6 Micropumps - Applications requiring higher flow rates can be done by combining pumps together, in either series for higher backpressure situations (600 mbar for liquid) or in parallel for higher flow rate (about 7 ml/min per pump for water).

Media Compatability of the mp6-pp - The mp6-pp is a polypropylene version of the micropump. This table shows the chemical resistance of the polyproplyene for different media.

Viscosity Effects on Pump Performance - This note discusses the effect of different viscosities on pump flow and pressure performance.

In addition, there are many other application notes and demonstration videos which may be of interest. 

See a listing of all application notes

Check out video demonstrations of the mp6 pump

Review technical specifications of the mp6 micropump