In this application note, we compare the flow accuracy and stability at low flow rates of two micropump drivers designed by Bartels Mikrotechnik GmbH: the mp-Lowdriver and mp-Highdriver. Mounted on the mp-Multiboard (main control board) and connected to a Bartels micropump, these pump drivers offer various ways of tuning the electrical signal applied to the pump.
Introduction to Bartels environment: the mp-Lowdriver and mp-Highdriver can be interfaced easily on the mp-Multiboard.
The mp-Multiboard is a complete interface with an Arduino microcontroller, which allows to connect and control mp6 micropumps, active valves, Sensirion SLF3S flow sensors and pressure sensors from the same software.
The Bartels micropumps are based on a piezo technology, and the input electrical signal has an impact on the performances of the pump. Therefore, 3 pump drivers have been developed: the mp-Lowdriver, the mp-Highdriver and the mp-Highdriver4. Unlike the mp-Lowdriver and the mp-Highdriver, the mp-Highdriver4 allows to control 4 pumps at the same time, while the other two allow to control only one pump at a time. We will focus on the mp-Lowdriver and mp-Highdriver, as the mp-Highdriver4 has the sames specifications than the mp-Highdriver.
Bartels Multiboard App: a unified user interface
Based on an Arduino framework, Bartels has developed an application to easily control any device connected to the mp-Multiboard. It allows you to vary the frequency and amplitude for each of the 4 pumps, close or open the 2 valves and, monitor the flow rate or pressure in real time.
In addition to this, it is possible to control the activation time of each of the pumps but also to determine which one should be switched off first. This app makes it easy to create small multi-step programs without any line of code!
mp-Lowdriver vs mp-Highdriver: which driver should you choose?
The mp-Lowdriver and mp-Highdriver micropump drivers were designed to meet the needs of researchers working between 5 µl/min and 10 ml/min. In microfluidics, flow rates under 100 µl/min are commonly used, and Bartels micropumps present a cost-effective alternative to current technologies. Comparing both pump drivers will help to choose the right driver for your application, but also to demonstrate the accuracy these micropumps and drivers can deliver.
Table 1: Comparison between the mp-Lowdriver and mp-Highdriver micropump drivers (Bartels Mikrotechnik GmbH).
| mp-Lowdriver | mp-Highdriver | |
| Dimensions | 10.16 x 25.4 x 2.64 mm | 10.16 x 25.40 x 2.82 mm |
| Amplitude | 0 to 150 Vpp | 10 to 150 Vpp |
| Frequency | 8 to 2000 Hz | 50 to 800 Hz |
| Signal form | sine, custom | sine, rectangular, custom |
Table 1: Comparison between the mp-Lowdriver and mp-Highdriver micropump drivers (Bartels Mikrotechnik GmbH).
The following flow measurements were made with a Sensirion SLF3S-0600F thermal flow sensor (+/- 5% accuracy on a range of +/- 2000 µl/min, min. accuracy of 0.5 µl/min), also used in the Bartels mpSmart-Lowdosing system.
mp-Lowdriver flow measurements
Two measurements at 5 and 10 µl/min were carried out with the mp-Lowdriver during a few seconds. These measurements allowed us to test the capabilities of the mp-Lowdriver at very low flow rates.
| mp-Lowdriver | 5 µl/min | 10 µl/min |
| Measured value (µl/min) | 5.22 | 10.86 |
| Standard error | 0.57 | 0.46 |
| Standard error (%) | 10.89 | 4.23 |
Table 2: Comparison between the target and measured values at 5 and 10 µl/min with a mp6-liq, mp-Multiboard and mp-Lowdriver (Bartels Mikrotechnik). Measured with a SLF3S-0600F (Sensirion) thermal flow sensor.
Figure 2: Actual flow rates with a mp6-liq micropump and mp-Lowdriver (Bartels Mikrotechnik) for target flow rates of 5 and 10 µl/min. Measured with a SLF3S-0600F flow sensor (Sensirion)
Bartels micropumps are indicated for flow rates higher than 5 µl/min. Though the mp-Lowdriver can go lower, the SLF3S-0600F flow sensor has a minimal accuracy of +/- 5% or 0.5 µl/min, which is only relevant for flow rates higher than 5 µl/min. The measurements realized at 5 and 10 µl/min show that the accuracy of the flow sensor is the limitation to accurately measure the output flow rates, but the flow accuracy is low enough to address most applications in microfluidics.
In order to better test the capabilities of the mp-Lowdriver, we have extended the measurement range beyond 10 µl/min to 50 µl/min. The results are shown below.
|
mp-Lowdriver |
20 µl/min |
30 µl/min |
40 µl/min |
50 µl/min |
|
Measured value (µl/min) |
21.04 |
30.57 |
39.99 |
51.21 |
|
Standard error |
0.53 |
1.30 |
1.47 |
0.89 |
|
Standard error (%) |
2.51 |
4.24 |
3.68 |
1.74 |
Table 3: Comparison between the target and measured values at 20, 30, 40 and 50 µl/min with a mp6-liq, mp-Multiboard and mp-Lowdriver (Bartels Mikrotechnik). Measured with a SLF3S-0600F (Sensirion) thermal flow sensor.
Figure 3: Actual flow rates with a mp6-liq micropump and mp-Lowdriver (Bartels Mikrotechnik) for target flow rates of 20, 30, 40 and 50 µl/min. Measured with a SLF3S-0600F flow sensor (Sensirion)
These results show that the mp-Lowdriver is very suitable for flow rates between 20 and 50 µl/min. Indeed, the error, in all cases, is less than 5% (flow sensor limit).
We can therefore conclude that the mp-Lowdriver can be used for applications requiring flow rates higher than 5 µl/min. Further tests should be done to address flow rates lower than 5 µl/min, using more accurate flow sensors.
mp-Highdriver flow measurements
We performed 4 measurements (50, 200, 500 and 850 µl/min) during a few seconds to test the capabilities of the mp-Highdriver for higher flow rates. The results are shown below.
|
mp-Highdriver |
50 µl/min |
200 µl/min |
500 µl/min |
850 µl/min |
|
Measured value (µl/min) |
51.62 |
202.86 |
498.09 |
849.35 |
|
Standard error |
0.96 |
1.05 |
1.86 |
2.79 |
|
Standard error (%) |
1.86 |
0.51 |
0.37 |
0.33 |
Table 4: Comparison between the target and measured values at 50, 200, 500 and 850 µl/min with a mp6-liq, mp-Multiboard and mp-Lowdriver (Bartels Mikrotechnik). Measured with a SLF3S-0600F (Sensirion) thermal flow sensor.
Figure 2: Actual flow rates with a mp6-liq micropump and mp-Highdriver (Bartels Mikrotechnik) for target flow rates of 50, 200, 500 and 850 µl/min. Measured with a SLF3S-0600F flow sensor (Sensirion).
The results for the mp-Highdriver are very satisfactory for the range tested. Indeed, the error, whatever the flow rate tested, is much lower than 2% (below the accuracy limit of the flow sensor) which reveals a very good stability of the device.
When discussing the target value of 50 µl/min measured with both mp-Lowdriver and mp-Highdriver, the results indicate very similar measured values. For this flow rate, the user has a choice between the mp-Lowdriver and the mp-Highdriver.
Conclusion
Bartels Mikrotechnik have created a powerful and easy-to-use environment to control and monitor fluids over a wide range of applications, from millifluidics to microfluidics. Coupled with the mp-Multiboard and a micropump, both mp-Lowdriver and mp-Highdriver offer efficient ways of driving fluids in a microfluidic system, with a good price/accuracy ratio.
Darwin Microfluidics is a worldwide distributor of Bartels products. Find all the components to create your microfluidic setup here!
