FAQ

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mp6 series

All wetted materials inside the standard mp6-hyb and mp6-gas are PPSU (PPSU and PI for the mp6-pi, PP and PI with the mp6-pp).

Please note that the mp6 is made with material of two grades of PPSU; natural-transparent and black. The lid is the natural grade with some blue colour additive.

The black PPSU material has some part of carbon black, see the related material safety data sheet for details. The other materials do not have carbon added. The mp6-series micropumps apply the technologies of laser welding and laser marking.

The mp6-series micropumps are made with material of two grades of PPSU: natural and black. The lid is the natural grade with some blue colour additive. Later, it will be switched to a black lid and transparent body, this improvement will allow the visual detection of air bubbles and particles in the pump chambers.

The adhesives that are used in the mp6 assembly are not in any contact with the liquid. However one of them, an epoxy, may contain carbon.

The functional principle of the Bartels micropumps 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. When the voltage decreases, the corresponding piezo deformation causes an upstroke of the membrane. The medium is sucked in and the chamber is filled again. In every second, the pump can do several hundreds of such pumping cycles. The pumping performance can be influenced by adjustment of the parameters.

The micropumps are capable of moving liquids with particles up to 50 µm. The smaller the particles the less risk of blockage. Depending on the particle material the particle load has influence. The higher the load the higher the risk of blockage. Blood particles are squishy and deformable which is not as problematic as for instance hard glass particles. Fibres are the most problematic particles as they easily get stuck.

If particles clog the pump different effects can be possible:

  • Pump rate may go down a bit with particles ladden media (based on liquid experiments), but this doesn’t need to indicate a possible blockage.
  • Partly blockage is present if the flow decreases further and does not recover when a media with no particles is pumped.
  • Severe blockage is present if flow and pressure generation is very low and cannot be regained.

It may be possible to clean the pump by pumping liquid for some time (TBD). However, if blocking particles can be rinsed out depends on the particles and the liquid as well as the kind of blockage. Fibres are nearly impossible to remove, same applies for very large particles.

The main causes for breakdown for long running times are the piezoceramic of the actuators and clogging of the fluidic path. Clogging can be avoided by filtering. The piezoceramic can be damaged by recurring voltage/current-spikes. So if the switch-on and switch-off action is done properly, i.e. without any voltage/current-spikes of the driving signal, the actuator will survive. If not, the piezoceramic will be damaged and the performance of the micropump will decrease.

If the pressure is the same inside and outside the pump, i.e. one tube connector is open to the surrounding, you can store it at any pressure you want. When the pump is inside a bag with some air and the bag is put under pressure this will be the same.

 

Everything needed is supplied by the electronic controllers offered by Bartels Mikrotechnik. The combination of signal, amplitude and frequency defines the performance of the micropump.

For laboratory applications, there is the extended micropump control mp-x. It is able to drive one micropump mp6, mp6-pi, mp6‑pp or mp6-AIR or two micropumps mp5 with different driving signals, the full range of amplitude and frequency manipulation and has an USB interface.

For quick starting with the micropumps, the evaluation boards mp6‑EVA and mp6‑QuadEVA offer easy to use controller hardware. The mp6-QuadKEY offers even more flexibility via an Arduino board.

For integration purposes in mobile devices, in devices of small construction sizes and generally onto PCBs of any kind, the OEM driver chips mp6-OEM and mp6-QuadOEM were designed to offer most of the functionality required to drive the micropumps.

The controllers mp-x, mp6-OEM and mp6-EVA from Bartels Mikrotechnik are optimized for driving a single mp6 pump. The mp6-QuadOEM and the mp6-QuadKEY allow controlling up to four mp6, mp6-pi, mp6-pp or mp6-gas micropumps up to a frequency of 800 Hz.

For serial applications we offer customized electronics that can be tailored to the customers’ requirements. Please contact us for more details.

We guarantee a lifetime of minimum 5.000 continuous working hours under lab conditions for the micropump mp6 series (>10.000 hours have been achieved without any notable failures). These values have been achieved by using a micropump from the mp6 series tested with the mp-x controller at 250 Vpp, 100 Hz for liquids and 300 Hz for gases and SRS signal. Even if we have reached more than 10,000 hours the warranty period of 5.000 hours has to be shared in this form, as the piezo supplier just guarantees this value.

If the pumps behave erratically, it is very often caused by improper priming. If air is still inside, which is on the one hand compressible and on the other hand uncontrollable to know when such an air bubble starts to come out, the flow rate can vary a lot.

NOTE:  For priming run the pump at max settings. The beginning of the priming may be difficult as plastic materials are in general hydrophobic, so that air bubbles may remain inside.

If the liquid is not degassed and remains inside the pump tiny gas bubbles will appear on the interior surfaces after some time. It is the same effect as in a glass of tap water. These gas bubbles are compressible and eat up a bit of actuator stroke and compression that lead to decreasing pump performance.

With high amplitudes of the pump the motion stress of the liquid is high and gas bubbles can be detached from the surfaces and transported out. The lower the amplitude of the pump the weaker the speed changes of the moved liquid during the actuator strokes hence gas bubbles are not removed.

The piezo actuators are driven by the electronic controller connected to the micropump. When the driving signal has fast amplitude changes and the set frequency is in the range of human perception, a sound can be heard. If a sinusoidal signal is used within low frequencies (e.g. up to 200 Hz), the lowest sound generation is reached. If a rectangular signal is used, the highest sound generation will be reached.

Evaluation Sets

Electronics

In general both parameters can be used. As lower amplitudes lead to lower compression in the pump chamber, it is better to do fewer large pump strokes over time. Therefore try to work at a high amplitude level and decrease the frequency until you reach the required flow rate level. In case the flow pulsation is too high, the amplitude should be lowered and frequency increased.

The mp-x controller generates three different signal forms: SRS, Sine, Rectangular. The mp6-OEM controller and the mp6-EVA board generates only one signal form, it is similar to rectangular. The mp6-QuadEVA board generates only one signal form as well – the sine signal. The mp6-QuadOEM controller and the mp6-QuadKEY board generate different signal forms: sine, rectangular and other.

The SRS signal is an optimized waveform generated by the mp-x controller to drive the actuator more efficiently. It makes the pump work at a lower sound level with increased long term stability of the flow rate. The SRS signal is used as the standard driving waveform.

With an electronic from the Quad-series it is possible to control up to four micropumps with one board, i.e. four pieces of mp6‑AIR micropumps. Nevertheless it is also possible to pump liquids, either with the mp6‑AIR; mp6‑pp, mp6-pi or the standard mp6 pump; though the higher frequencies will then not result in a performance boost.

  • The mp6-QuadOEM controller comes in a package similar to an integrated circuit that enables integration into system electronics or on a PCB. The driving frequency, amplitude and also the driving signal is adjustable. Every pump can be activated and deactivated individually. This driver is configured and controlled through an I2C interface.
  • With the mp6-QuadKEY you can control the mp6-QuadOEM controller through an Arduino Nano or pin compatible microcontroller. An external power supply terminal is available, but the board can also be powered through the microcontroller USB port. It comes with a demo software and a source code (LabView).

Driving the micropump with the mp-x allows you to gather comprehensive results in short time. You will also be able to consider the sometimes complex interaction of micro- and macrofluidics with direct measurements of your system right from the beginning. Furthermore you will also be able to conclude about how to integrate the micropump into any of your systems.

For that purpose you can connect the mp-x via USB-port with a PC, manually control it with the NI‑LabView interface and turn it into a fully automatized control. Experiments with systems in which pressure-, flow- or other –sensors gather additional data are easily achievable. You can start with basic LabView routines that we implemented already for you.

Independent of the NI‑LabView develop environment you can choose every other computer language that can handle the communication with an emulated serial interface.

Applications

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