Case study: Active sensor feeding with micropumps
May 2021

Case Study

Active Sensor feeding with micropumps
What is microfluidics?
Microfluidics is the fine art of creation and manipulation of small portions of fluids, often realized by flow
within small, sub-millimeter-scale channels. These small dimensions allow the fluid flow to be controlledwith exquisite precision (Seifert, Thiele; 2020).
Microfluidic systems are used in many applications, including medical testing, drug delivery, chemical
analysis, chip cooling, etc. These systems have the advantages of small volume, low cost, high throughput
analysis (Gidde; 2020).
Further use of this method in the realm beyond academic research, such as that of commercial finechemical production, sensor development, or encapsulation of active substances, is presently being
explored. Microfluidics, though, is a demanding field and working area that requires both profoundtheoretical understanding and experimental skills. As there is no standard in education and training on
this method in many fields of study that actually can benefit most from this technique (Seifert, Thiele).
Micropumps are essential components in the microfluidic systems and are used to manipulate, transportand control the precise quantity of fluid in terms of microlitre and millilitre (Gidde; 2020). Comparing withthe conventional syringe pumps, microfluidic pumps have the capability of combining with other on-chips
functional units to realize portable micro total analysis systems (μTAS) (Gao; 2020). Micropumps havebeen developed on various principles for many different applications viz. drug delivery and biomedicalassays (Gidde; 2020).

About the mp6 micropump
The available, industrialized and commercialized example is the mp6 micropump by Bartels MikrotechnikGmbH. This micro pump is a positive displacement membrane pump utilizing piezo buzzers. With a volumeof 2250 mm3 (30 mm x 15 mm x 5 mm) it is, as a micro pump, dimensionally very beneficial.
It is built up in a „sandwich“ (stack) setup and combined and sealed in laser welding process.

There is absorbing and transparent plastic material that can be melted by a laser, so that the melted mass
unites the parts. There is no glue in contact with the fluid, but only the material the micropump is madefrom. Standard materials are PPSU, PI and PP. Due to the unibody and the fact that the pump does notcontain any moving parts, it is sterilizable, robust and reliable with a lifetime with more than 5000 h. The
micropump possesses two membrane stages in a series setup running with a 180° shift.

All values are approximate and no guarantee of specific technical properties.
Changes in the course of technical progress are possible without notice.

Case study: Active sensor feeding with micropumps
May 2021
These two stages behave like two micropumps in series doubling the pressure. Besides, this principle makes
it much more tolerant regarding gas bubbles. The mp6 is running at high voltages which regulate thebending of the piezo membranes and the frequencies which define the number of displacements per
second. The available ranges are 0-250 Vpp and 1-600 Hz. These electronic parameters applied to the piezo
membranes lead to the following typical fluidic values of the pump:▪
▪

Liquids (eta = 1 mPas): q = 5 - 8000 µl/min in free flow and p > 600 mbar
Gas: q > 25 ml/min in free flow and p > 150 mbar

The flow rate depends on the pressure. In addition, the performance of the mp6 is dependent on theviscosity of the liquids.
The mp6 micropump is made in Germany and leaves the factory after a 100% OQC.

Active sensor feeding with micropumps
Together with the request for higher safety
and efficiency in industrial processes, the useof sensors increases continuously. To
generate stable and defined measurement
values in these processes, the environmental
conditions of the sensor need to be kept at aconstant level. This especially applies tofeeding the sensor with an analyte fluid.
Besides a faster response to changing
analyte properties, a lowered target
concentration at the point of measurement
can be balanced as applied for catalytic
sensors for example.
As because of these reasons various sensors
can not be used with completely passive feeding, micropumps from Bartels Mikrotechnik open up new
fields of application. Due to their simple setup, they can be produced at a low cost level and with their
particle tolerance they prove performance under real conditions.
With its small dimensions, the pump can either be used as a subassembly together with the sensor or as
an OEM component to be integrated into a more complex unit. Especially for portable instruments, whereminiaturization plays an important role, the low energy consumption comes into play. Battery operation
can be easily realized. Dependent on the customers need the driving electronics can be either integrated
into the main PCB of the unit or even inside an enlarged pump housing.
The use of an inert polymer in combination with an optimized placement of the pump inside the systemenables operation also under difficult conditions.
The micropump mp6 provides a minimum flow rate of 6 ml/min with liquids and 18 ml/min with gases. By
using the available evaluation kit, the pump performance can be tested in the target application and thedriving parameters can be defined.
In a customer application, the pump has been used to monitor a mixture of hydrogen, oxygen and nitrogengas. Using a bypass channel, gas was extracted for analysis and fed to the sensor. During the systemevaluation of the pump, characteristic flow rates in dependence on driving voltage and frequency havebeen determined, as shown in the first graph.

All values are approximate and no guarantee of specific technical properties.
Changes in the course of technical progress are possible without notice.

Case study: Active sensor feeding with micropumps
May 2021

In a second application, a CO2 gas sensor fromthe company Sensirion was directly exposed toa changing CO2 concentration, once directly
and once by using of an mp6 micropump.
The direct couoling of the test gas to the test
beam slope of the IR sensor shows a significant
improvement in the time response.

1,1

Relatives Signal

The second graph shows the dependency
between the relative sensor signal and the gasflow. On the one hand this shows the signal
improvement with active sensor feeding, on theother hand the need to provide a stable flowrate throughout the measurement.

0,9Sensor 1Sensor 20,70,50,336912Flussrate [ml/min]

15Besides standard components, Bartels microComponents is specialized in the development of application
specific pumps and system integration

Bartels Mikrotechnik is a globally active manufacturer and development service provider inthe field of microfluidics. In the microEngineering division, the company supports industrial
customers in the modification, adaptation and new development of high-performance andmarket-oriented product solutions through the innovative means of microsystems technology.
The second division, microComponents, produces and distributes microfluidic products andsystems, especially for miniaturized and portable applications. Our key products aremicropumps that convey smallest quantities of gases or liquids and are used in a variety ofways in biotechnology, pharmaceuticals, medical technology and numerous other applications.
Bartels Mikrotechnik with passion for microfluidics!

Follow us:Contact us:
Bartels Mikrotechnik GmbH
Konrad-Adenauer-Allee 1144263 Dortmund Germany

www.bartels-mikrotechnik.de
info@bartels-mikrotechnik.de
Tel: +49-231-47730-500

All values are approximate and no guarantee of specific technical properties.
Changes in the course of technical progress are possible without notice.