CASE
STUDY

Characterization of
mp6-micropump-driven
vibrating meshes

July 2021
Authors:
Florian Siemenroth
Udo Janzyk
Alexander Friebe

Case study: mp6-micropump-driven vibrating meshes
July 2021

Controlled nebulization ofdifferent liquids

Active fluid
transportation

Medical, LiveScience,Automotive

In strongly growing fields of Medical, Lifescience, Automotive, Aerospace and several otherindustries, the controlled nebulization of different kinds of liquids by advanced products istremendously increased. In order to keep the needed devices as small as possible not only pipes,
valves and connectors for fluid passage have to be miniaturized. Of even equal importance: the active
element for fluid transportation.
For that purpose, we investigated Vibrating Meshes of two different well-known suppliers whichwere driven by our mp6 micropumps. In addition, we performed several reference experiments for
fluid delivery to the mesh. The results demonstrate unbeatable advantages, which recommend themp6 micropump for that task.
Figure 1:
Product photo of a “Premounted” Aerogen-Mesh(left above); Model “Solo”,
surface (Topside = Inlet)
with 100fold (right above)and 500fold (below)
magnification.

The Aerogen Mesh exhibit a pore size of ~5,1 µm for the droplet generation while the complete “InletFunnel” show a diameter of ~ 108 µm. The distance of the pores was determined to be ~ 117 µm; thisresult represents quite common values for Meshes on the market for numerous applications. Besides theAerogen-Mesh we implemented 2 different Meshes from Optnics. Figure 2a shows the second kind ofMesh(es), used in this study.

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

Case study: mp6-micropump-driven vibrating meshes
July 2021
Figure 2:left (a), interieur of anOptnics Mesh; right (b),mp6 micropump ofBartels Mikrotechnik(Photo taken in 2017).
Figure 2b introduces our mp6 micropump which acts as an excellent Mesh-Driver. For this study we havedesigned four different experiments in sum to demonstrate the possibilities of applications as well as theflexibility which can be achieved in combination with the mp6 micropump. The following Figure 3illustrates Experiments #1 - #3.
Figure 3:Experiments #1 - #3
(with gas permeablehydrophobic seal) for
nebulization ofliquids, performed inBartels` laboratories.

In all experiments, our Malvern-Spraytec-Analyzer has been used for the determination of the generated
particle sizes. This method of particle characterization is based on light scattering; monochromatic lightsource: He-Ne-Laser (633 nm wavelength). Experiment #1. A small amount of 200 µL Liquid is placed on
the Mesh-Inlet. Experiment #2. Much more applicable, the Mesh is equipped with a reservoir of ~6000 µL
for liquid which enables a much longer operating time. Experiment #3, advantages in summary. If 2 pcs.
of mp6 micropumps are even combined, an extremely extended duration of nebulization can be achieved,
because the reservoir can contain a much higher amount of liquid and rather be placed elsewhere in athinkable “Device”; i.e., right next, above or below – the mp6 pump can deliver “upwards” to the mesh –the place of nebulization; the porous seal prevents a loss of liquid. Furthermore, due to the design of theset-up, the mesh can be orientated in any direction for continuous runs.
Table 1 summarizes the results of these experiments. For that, we have chosen 2 different meshes fromOptnics – one size below and one size above the Aerogen-Mesh with respect to its pore diameter (small:~4,4 µm = Optnics-Mesh #A vs. medium ~5,1 µm Aerogen-Mesh vs. huge: ~7,5 µm Optnics-Mesh #B).

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

Case study: mp6-micropump-driven vibrating meshes
July 2021
Several aspects of the results have to be highlighted. Nebulization of ethanol, often used as a solvent for
medical drugs, led to a bit smaller particle size as compared to water. This effect could be compensated byan increased pore diameter if ~5 µm particles are desired (~4,4 µm → ~6 µm pore diameter). The mostinteresting point is the measured volume flowrate if the delivery by a reservoir (Experiment #2) is comparedwith those of a mp6-driven set-up in experiment #3. In the experiments with mesh #A & #B, the mp6
micropumps were adjusted to ~50% of their capacity (~125 Vpp = ~4 mL/min @ 60 Hz). It can be seenthat meshes with “common” pore sizes such as Optnics Mesh #A as well as the Aerogen-Mesh can beemphasized to the 2fold nebulization-effectivity. In conclusion, a mp6-driven mesh is delivered by“convection” and not by a simple steady bulk of liquid in a reservoir.
Figure 4 below shows a typical test set-up using the Aerogen-Mesh in combination with 2 pcs. of mp6
during the characterization of the particle size.

Figure 4:
Experiment #3, Aerogen-Mesh (Reservoir open; equal to flexible), forward & backward-pipes, driver-cable,
mp6 micropumps and pressure less liquid source, respectively; components mounted in the actually active
Malvern-Spraytec-Analyzer.
Figure 5a-f below presents six randomly selected plots of “Particle-Frequency” & cum. Volume vs. Particle
Diameter. The most relevant information is that in any case the change from the “Reservoir-Driven Mesh”
to the “mp6-Driven Mesh” (i.e., a → b, c → d and e → f) led not to a significant change with respect tothe calculated Dv50-Particle-Size. Relevant data in Figure 7 (incl. standard deviation) below clearlysupports that finding. A negligible, not relevant change in case of the Size-Distribution can be detected
for Mesh #A of Optnics (4,4 µm Pore Diameter) and Aerogen (5,1µm). In order to compensate / modulate
this minor effect, we are working on optimization of the mp6-Frequency beyond 60Hz, even downwards
or upwards as well as its waveform. In contrast, Mesh #B of Optnics (~7,5 µm Pore-Size) shows nearly nochange which clearly indicates that the smaller meshes were not driven in the 100% optimal “Window”.

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

Case study: mp6-micropump-driven vibrating meshes
July 2021

Figure 5a-f:(in general, from left to right, Reservoir-driven → mp6-driven): a&b above, Mesh #A from Optnics; c&d in
the center, Mesh #B from Optnics; e&f below, Mesh from Aerogen.
Finally, in order to vary the manner of spraying, Figure 6 shows Experiment #4. Here, we orientated two
reservoir-driven meshes from Aerogen in an angle of 90° to each other. Also in this experiment, the “SweetSpot” to interfere with the laser beam of the Malvern-Spraytec-Analyzer was adjusted to be ~5 cm behindthe operating mesh, inhere, the chosen collision point of both meshes was the same.
Figure 6:
Reservoir-driven “Dual-Mesh-Setup” Experiment #4 using
two meshes from Aerogen. “Sweet-Spot” = point ofmeasurement = 5cm.

In all performed experiments, we have detected no significant differences of the measured Dv50-Value forthe generated particle size, no matter if ethanol or water was sprayed, single or dual. The desired, inhalable
particle size of ~5 µm is maintained, even, as long as the pore size is approx. 5 µm or smaller. Figure 7
summarizes the core results of our study.

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

Case study: mp6-micropump-driven vibrating meshes
July 2021
Figure 7:
Data-Summary ofvarious SprayExperiments; 128 kHz
Aerogen-Driver (vs.
108 kHz OptnicsDriver, cf. Table 1).

By evaluating the data presented in Figure 7, we can conclude that both, critical medical formulations canbe sprayed by dual-driven meshes as well as mp6-driven runs will perform equal in order to guarantee thedesired Dv50-Value with respect to the particle size. In many cases, medical drugs are not soluble in water,
hence, ethanol is the solvent of choice (or mixtures of both).
In the next step of this study, we enlarged the range of application in order to clarify another relevant
issue: not every medical formulation deals with the viscosity of water or ethanol (1,0 . . . ν . . . 1,2 cP @20°C). For that purpose, we selected two “Model-Compounds”, namely, saccharose (table sugar) andglycerin (99%, pure) for increase of the viscosity of aqueous test-solutions. Figure 8 below summarizes theresults of the Particle-Size distribution (Dv50-Value) vs. viscosity of the model-Solution of both SystemSpecies; Mesh vs. Collision-Nozzle.
Figure 9: Particle size
distribution (Dv50) vs. viscosityof the nebulized ModelLiquids.

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

Case study: mp6-micropump-driven vibrating meshes
July 2021
Surprisingly, if the solutions` viscosity is suggestively increased, the Aerogen-Mesh maintains the Dv50value. We assume that this result is caused by the mechanism of the particle generation. The Mesh forms
the droplets by shaking off the liquid “piece-by-piece” from the ends of the filled outlet-funnels. Anothercorrelating point is that the mesh does not operate any more, if the viscosity is more than ~3,5 cP. In thatcase, Mesh`s Driving-Force for shaking off the liquid tents to be smaller as compared to the needed force
for “pore-dewetting” (5,1 µm Outlets of the Mesh).

Outlook: Ongoing experiments (in progress) have shown that Mesh #B from Optnics (~7,5 µm Porediameter) shifts the data points of Mesh #A simply upwards, parallel the x-Axis, independently from theviscosity. This indicated a brilliant tool for the controlled particle generation with every desired dropletdiameter.

Components and systems used:
••••
•
•

mp6 micropump by Bartels Mikrotechnik
mp-Labtronix by Bartels Mikrotechnik
vibrating mesh “Solo” by Aerogen
two vibrating meshes by Optnics
Saint-Gobain Tygon LMT-55
Malvern Spraytec Analyzer

Acknowledgement:
Our Partner, Aerogen from Galway, Ireland,
was instrumental in defining our researchpath, whereby we were able to develop agreat solution for active and accurate
atomization of liquids generating a welldefined aerosol. For that, we are extremely grateful and we are looking forward to our close collaboration.
In case you are interested in the above-described microfluidic solution for mist generation or if you areinterested in getting in touch with either one of us, Aerogen or Bartels Mikrotechnik, please feel free tocontact us. You can find the contact details below.

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

Case study: mp6-micropump-driven vibrating meshes
July 2021

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!

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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.